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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Trading Symbol	CASA
Entity Registrant Name	Casa Systems Inc
Entity Central Index Key	0001333835
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		82,774,851

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 308,350	$ 260,820
Accounts receivable, net of provision for doubtful accounts of $686 and $692 as of September 30, 2018 and December 31, 2017, respectively	79,750	122,634
Inventory	41,233	36,148
Prepaid expenses and other current assets	3,627	5,151
Prepaid income taxes	299	538
Total current assets	433,259	425,291
Property and equipment, net	29,641	29,363
Accounts receivable, net of current portion	3,062	4,710
Deferred tax assets	18,791	9,718
Other assets	3,091	615
Total assets	487,844	469,697
Current liabilities:
Accounts payable	17,796	15,833
Accrued expenses and other current liabilities	34,864	48,250
Accrued income taxes	172	118
Deferred revenue	30,085	34,224
Current portion of long-term debt, net of unamortized debt issuance costs	2,173	2,156
Total current liabilities	85,090	100,581
Accrued income taxes, net of current portion	9,120	8,810
Deferred revenue, net of current portion	14,094	14,691
Long-term debt, net of current portion and unamortized debt issuance costs	293,824	295,459
Total liabilities	402,128	419,541
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000 shares authorized as of September 30, 2018 and December 31, 2017; no shares issued and outstanding as of September 30, 2018 and December 31, 2017
Common stock, $0.001 par value; 500,000 shares authorized as of September 30, 2018 and December 31, 2017; 84,847 and 81,043 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	85	81
Additional paid-in capital	153,580	128,798
Accumulated other comprehensive income (loss)	(1,426)	194
Accumulated deficit	(66,523)	(78,917)
Total stockholders’ equity	85,716	50,156
Total liabilities and stockholders’ equity	$ 487,844	$ 469,697

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Provision for doubtful accounts	$ 686	$ 692
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares, outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	84,847,000	81,043,000
Common stock, shares outstanding	84,847,000	81,043,000

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total revenue	$ 71,506	$ 94,259	$ 229,302	$ 233,613
Cost of revenue:
Total cost of revenue	14,575	25,266	61,015	66,502
Gross profit	56,931	68,993	168,287	167,111
Operating expenses:
Research and development	16,403	15,217	53,629	43,912
Sales and marketing	10,234	8,747	31,123	26,983
General and administrative	7,671	4,866	21,401	14,387
Total operating expenses	34,308	28,830	106,153	85,282
Income from operations	22,623	40,163	62,134	81,829
Other income (expense):
Interest income	1,821	600	4,596	1,674
Interest expense	(5,032)	(4,483)	(14,579)	(12,937)
Gain (loss) on foreign currency, net	69	138	(445)	773
Other income, net	411	193	978	632
Total other income (expense), net	(2,731)	(3,552)	(9,450)	(9,858)
Income before provision for (benefit from) income taxes	19,892	36,611	52,684	71,971
Provision for (benefit from) income taxes	995	12,288	(5,406)	12,334
Net income	18,897	24,323	58,090	59,637
Other comprehensive (loss) income—foreign currency translation adjustment	(1,117)	560	(1,620)	1,279
Comprehensive income	17,780	24,883	56,470	60,916
Net income attributable to common stockholders:
Basic	18,897	10,390	58,090	7,689
Diluted	$ 18,897	$ 11,795	$ 58,090	$ 7,689
Net income per share attributable to common stockholders:
Basic	$ 0.22	$ 0.31	$ 0.69	$ 0.23
Diluted	$ 0.21	$ 0.27	$ 0.62	$ 0.18
Weighted-average shares used to compute net income per share attributable to common stockholders:
Basic	86,167	33,701	83,701	33,657
Diluted	92,032	43,123	93,180	43,198
Product
Revenue:
Total revenue	$ 60,817	$ 84,196	$ 199,544	$ 205,155
Cost of revenue:
Total cost of revenue	13,272	23,824	57,612	62,865
Service
Revenue:
Total revenue	10,689	10,063	29,758	28,458
Cost of revenue:
Total cost of revenue	$ 1,303	$ 1,442	$ 3,403	$ 3,637

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - 9 months ended Sep. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balances at Dec. 31, 2017	$ 50,156	$ 81	$ 128,798	$ 194	$ (78,917)
Balances, shares at Dec. 31, 2017		81,043
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes	14,022	$ 7	14,015
Exercise of stock options and common stock issued upon vesting of equity awards, net of shares withheld for employee taxes, shares		6,894
Foreign currency translation adjustment, net of tax of $0	(1,620)			(1,620)
Follow-on offering selling stockholders profit disgorgement, net of offering costs of $41	3,770		3,770
Stock repurchase program	(45,699)	$ (3)			(45,696)
Stock repurchase program, shares		(3,090)
Stock-based compensation	6,997		6,997
Net income	58,090				58,090
Balances at Sep. 30, 2018	$ 85,716	$ 85	$ 153,580	$ (1,426)	$ (66,523)
Balances, shares at Sep. 30, 2018		84,847

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Statement Of Stockholders Equity [Abstract]
Foreign currency translation adjustment, tax	$ 0
Follow-on offering selling shareholders profit disgorgement, offering costs	$ 41

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)
$ in Thousands

9 Months Ended

Sep. 30, 2018

Sep. 30, 2017

Cash flows from operating activities:

Net income

$ 58,090

$ 59,637

Adjustments to reconcile net income to net cash provided by operating activities:

Depreciation and amortization

7,037

5,576

Stock-based compensation

6,542

5,893

Deferred income taxes

(9,130)

1,347

Decrease in provision for doubtful accounts

(6)

Excess and obsolete inventory valuation adjustment

(3,185)

673

Changes in operating assets and liabilities:

Accounts receivable

38,062

Inventory

(3,344)

13,074

Prepaid expenses and other assets

(849)

1,651

Prepaid income taxes

238

Accounts payable

4,309

(16,694)

Accrued expenses and other current liabilities

549

(2,331)

Accrued income taxes

383

(4,558)

Deferred revenue

(4,594)

(15,280)

Net cash provided by operating activities

94,102

49,054

Cash flows (used in) provided by investing activities:

Purchases of property and equipment

(6,224)

(4,703)

Proceeds from maturities of marketable securities

14,589

Net cash (used in) provided by investing activities

(6,224)

9,886

Cash flows used in financing activities:

Principal repayments of debt

(2,476)

(2,468)

Proceeds from exercise of stock options

14,035

204

Payments of dividends and equitable adjustments

(6,472)

(198,187)

Follow-on offering selling stockholders profit disgorgement

3,811

Repurchases of common stock

(45,699)

Payments of initial public offering costs

(1,148)

(1,511)

Employee taxes paid related to net share settlement of equity awards

(13)

(3,788)

Net cash used in financing activities

(37,962)

(205,750)

Effect of exchange rate changes on cash and cash equivalents

(1,374)

775

Net increase (decrease) in cash, cash equivalents and restricted cash

48,542

(146,035)

Cash, cash equivalents and restricted cash at beginning of period

260,820

329,554

Cash, cash equivalents and restricted cash at end of period

^[1]

309,362

183,519

Supplemental disclosures of cash flow information:

Cash paid for interest

13,441

12,197

Cash paid for income taxes

4,252

15,204

Supplemental disclosures of non-cash operating, investing and financing activities:

Purchases of property and equipment included in accounts payable

963

901

Prepaid expenses and other current assets included in accounts payable

515

Deferred public offering costs included in accounts payable and accrued expenses and other current liabilities

Unpaid equitable adjustments included in accrued expenses and other current liabilities

4,189

9,178

Release of customer incentives included in accounts receivable and accrued expenses and other current liabilities

$ 6,314

$ 13,930

[1]	See Note 2 of the accompanying notes for a reconciliation of the ending balance of cash, cash equivalents and restricted cash as shown in these condensed consolidated statements of cash flows.

Nature of Business and Basis of Presentation	9 Months Ended
Nature of Business and Basis of Presentation	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	1. Nature of Business and Basis of Presentation Casa Systems, Inc. (the “Company”) was incorporated under the laws of the State of Delaware on February 28, 2003. The Company is a global communications technology company headquartered in Andover, Massachusetts and has wholly owned subsidiaries in China, France, Canada, Ireland, Spain, Colombia and the Netherlands. The Company offers solutions for next-generation centralized, distributed and virtualized architectures for cable broadband, fixed-line broadband and wireless networks. The Company’s solutions enable customers to cost-effectively and dynamically increase network speed, add bandwidth capacity and new services for consumers and enterprises, reduce network complexity and reduce operating and capital expenditures. The Company is subject to a number of risks similar to other companies of comparable size and other companies selling and providing services to the communications industry. These risks include, but are not limited to, the level of capital spending by the communications industry, a lengthy sales cycle, dependence on the development of new products and services, unfavorable economic and market conditions, competition from larger and more established companies, limited management resources, dependence on a limited number of contract manufacturers and suppliers, the rapidly changing nature of the technology used by the communications industry and reliance on resellers and sales agents. Failure by the Company to anticipate or to respond adequately to technological developments in its industry, changes in customer or supplier requirements, changes in regulatory requirements or industry standards, or any significant delays in the development or introduction of products could have a material adverse effect on the Company’s operating results, financial condition and cash flows. In December 2017, the Company closed its initial public offering (“IPO”) of 6,900 shares of its common stock at an offering price of $13.00 per share, including 900 shares pursuant to the underwriters’ option to purchase additional shares of the Company’s common stock. The Company received net proceeds of $79,327, after deducting underwriting discounts and commissions of $6,279 and offering costs of $4,094. Upon the closing of the IPO, all 4,038 shares of the Company’s then-outstanding preferred stock automatically converted on a ten-for-one basis into an aggregate of 40,382 shares of the Company’s common stock. Upon conversion of the preferred stock, the Company reclassified $97,439 from temporary equity to additional paid-in capital and $40 from temporary equity to common stock. On April 30, 2018, the Company closed its follow-on offering in which certain stockholders sold 7,350 shares of the Company’s common stock at a price of $25.00 per share, before deducting underwriting discounts and commissions (the “follow-on offering”). The Company did not sell any common stock in the follow-on offering and did not receive any of the proceeds from the sale of the Company’s common stock by the selling stockholders. In connection with the sale of the Company’s common stock in the follow-on offering, certain of the selling stockholders disgorged $3,770 of profits recognized from the sale, after deducting $41 of offering costs, to the Company in accordance with Section 16(b) of the Securities Exchange Act of 1934, as amended, which was recorded as an increase in additional paid-in capital. The Company incurred $856 of transaction costs in connection with the follow-on offering, of which $815 was recorded in general and administrative expenses in the accompanying condensed consolidated statements of operations. The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”), and may remain an emerging growth company until the last day of the fiscal year following the fifth anniversary of the initial public offering, subject to specified conditions. The JOBS Act provides that an emerging growth company can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected not to “opt out” of such extended transition period, which means that when a standard is issued or revised and it has different application dates for public or private companies, the Company will adopt the new or revised standard at the time private companies adopt the new or revised standard, provided that the Company continues to be an emerging growth company. The JOBS Act provides that the decision to take advantage of the extended transition period for complying with new or revised accounting standards is irrevocable. The accompanying condensed consolidated balance sheet as of September 30, 2018, the condensed consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2018 and 2017, the condensed consolidated statements of cash flows for the nine months ended September 30, 2018 and 2017 and the condensed consolidated statements of stockholders’ equity for the nine months ended September 30, 2018 are unaudited. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2018 and 2017 are also unaudited. The accompanying condensed consolidated balance sheet as of December 31, 2017 was derived from the Company’s audited consolidated financial statements for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 7, 2018 (the “Annual Report on Form 10-K”). The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) regarding interim financial reporting. Certain information and note disclosures normally included in the consolidated financial statements prepared in accordance with GAAP have been condensed or omitted. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Annual Report on Form 10-K. There have been no material changes to the Company’s accounting policies from those disclosed in the Annual Report on Form 10-K that would have a material impact on the Company’s condensed consolidated financial statements. The unaudited interim condensed consolidated financial statements have been prepared on a basis consistent with that used to prepare the audited annual consolidated financial statements and, in the opinion of management, include all adjustments, consisting of only normal recurring adjustments, necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods, but are not necessarily indicative of the results of operations and cash flows to be anticipated for the full year ending December 31, 2018 or any future period. The accompanying condensed consolidated financial statements include the accounts and results of operations of the Company and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods.

Significant estimates and judgments relied upon by management in preparing these condensed consolidated financial statements include revenue recognition, provision for doubtful accounts, reserves for excess and obsolete inventory, valuation of inventory and deferred inventory costs, the expensing and capitalization of software-related research and development costs, amortization and depreciation periods, recoverability of net deferred tax assets, valuations of uncertain tax positions, provision for income taxes, warranty allowances, the valuation of the Company’s common stock and other equity instruments, and stock-based compensation expense.

Although the Company regularly reassesses the assumptions underlying these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period in which they become known. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances existing at the time such estimates are made.

Cash, Cash Equivalents and Restricted Cash

Cash and cash equivalents include all highly liquid investments maturing within three months from the date of purchase. As of September 30, 2018 and December 31, 2017, the Company’s cash and cash equivalents consisted of investments in certificates of deposit, commercial paper and money market mutual funds.

Restricted cash, which was included in other assets as of September 30, 2018, consisted of a certificate of deposit of $1,000 pledged as collateral for a stand-by letter of credit required to support a contractual obligation. The Company did not have any restricted cash as of December 31, 2017.

The following table is a reconciliation of cash, cash equivalents and restricted cash included in the accompanying condensed consolidated balance sheets that sum to the total cash, cash equivalents and restricted cash included in the accompanying condensed consolidated statements of cash flows:

	September 30, 2018		September 30, 2017
Cash and cash equivalents	$	308,350	$	183,519
Restricted cash included in other assets		1,012		—
	$	309,362	$	183,519

Accounts Receivable

Accounts receivable are presented net of a provision for doubtful accounts, which is an estimate of amounts that may not be collectible. Accounts receivable for arrangements with customary payment terms, which are one year or less, are recorded at invoiced amounts and do not bear interest. The Company generally does not require collateral, but the Company may, in certain instances based on its credit assessment, require full or partial prepayment prior to shipment.

For certain customers and/or for certain transactions, the Company provides extended payment arrangements to allow the customer to pay for the purchased equipment in monthly, other periodic or lump-sum payments over a period of one to five years. Certain of these arrangements are collateralized by the underlying assets during the term of the arrangement. Payments due beyond 12 months from the balance sheet date are recorded as non-current assets. In addition, amounts recorded as current and non-current accounts receivable for extended payment term arrangements at any balance sheet date have a corresponding amount recorded as deferred revenue because the Company defers the recognition of revenue for all extended payment term arrangements and only recognizes revenue to the extent of the payment amounts that become due from the customer.

Although there is no contractual interest rate for customer arrangements with extended payment terms, the Company imputes interest on the accounts receivable related to these arrangements and reduces the arrangement fee that will be recognized as revenue for the amount of the imputed interest, which is recorded as interest income over the payment term using the effective interest method. For the periods presented in the accompanying condensed consolidated financial statements, the impact of imputing interest on revenue and interest income was insignificant.

Accounts receivable as of September 30, 2018 and December 31, 2017 consisted of the following:

	September 30, 2018		December 31, 2017
Current portion of accounts receivable, net:
Accounts receivable, net	$	72,721	$	106,114
Amounts due from related party (see Note 14)		4,707		13,367
Accounts receivable, extended payment arrangements		2,322		3,153
		79,750		122,634
Accounts receivable, net of current portion:
Accounts receivable, extended payment arrangements		3,062		4,710
	$	82,812	$	127,344

The Company performs ongoing credit evaluations of its customers and, if necessary, provides a provision for doubtful accounts and expected losses. When assessing and recording its provision for doubtful accounts, the Company evaluates the age of its accounts receivable, current economic trends, creditworthiness of the customers, customer payment history, and other specific customer and transaction information. The Company writes off accounts receivable against the provision when it determines a balance is uncollectible and no longer actively pursues collection of the receivable. Adjustments to the provision for doubtful accounts are recorded as general and administrative expenses in the condensed consolidated statements of operations and comprehensive income.

As of September 30, 2018 and December 31, 2017, the Company concluded that all amounts due under extended payment term arrangements were collectible and no reserve for credit losses was recorded. During the nine months ended September 30, 2018 and 2017, the Company did not provide a reserve for credit losses and did not write off any uncollectible receivables due under extended payment term arrangements.

Concentration of Risks

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and accounts receivable. Cash and cash equivalents consist of demand deposits, savings accounts, commercial paper, money market mutual funds, and certificates of deposit with financial institutions, which may exceed Federal Deposit Insurance Corporation limits. The Company has not experienced any losses related to its cash and cash equivalents and does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

Significant customers are those that represent 10% or more of revenue or accounts receivable and are set forth in the following tables:

	Revenue
	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Customer A		35	%		58	%		29	%		36	%
Customer B	*			*			*				11	%
Customer C		21	%	*				16	%	*
Customer D		11	%	*			*			*
Customer E		10	%	*			*			*

	Accounts Receivable, Net
	September 30,			December 31,
	2018			2017
Customer A		28	%		44	%
Customer B	*				10	%
Customer C		32	%	*
Customer D	*				17	%

*	Less than 10% of total

Customer B is a related party, Liberty Global Affiliates (see Note 14).

Certain of the components and subassemblies included in the Company’s products are obtained from a single source or a limited group of suppliers. In addition, the Company primarily relies on two third parties to manufacture certain components of its products. Although the Company seeks to reduce dependence on those limited sources of suppliers and manufacturers, the partial or complete loss of certain of these sources could have a material adverse effect on the Company’s operating results, financial condition and cash flows and damage its customer relationships.

Impact of Recently Adopted Accounting Standards

In November 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASU 2016-18”), which requires that amounts generally described as restricted cash or restricted cash equivalents be included with cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The standard is effective for public companies for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. The standard is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual periods beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. The Company retrospectively adopted ASU 2016-18 during the second quarter of 2018, and there was no material impact on its condensed consolidated financial statements.

Impact of Recently Issued Accounting Standards

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes existing revenue recognition guidance under GAAP. The core principle of this standard is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delays the effective date of ASU 2014-09 such that the standard is effective for public companies for annual periods beginning after December 15, 2017 and for interim periods within those fiscal years. The standard is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual reporting periods beginning after December 15, 2018. Entities are not permitted to adopt the standard earlier than the original effective date for public entities. This standard can be adopted either retrospectively to each prior reporting period presented or as a cumulative effect adjustment as of the date of adoption. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (“ASU 2016-08”), which further clarifies the implementation guidance on principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing (“ASU 2016-10”), clarifying the implementation guidance on identifying performance obligations and licensing. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), which clarifies the objective of the collectibility criterion, presentation of taxes collected from customers, non-cash consideration, contract modifications at transition, completed contracts at transition and how guidance in ASU 2014-09 is retrospectively applied. ASU 2016-08, ASU 2016-10 and ASU 2016-12 have the same effective dates and transition requirements as ASU 2014-09. The Company continues to assess the potential impact that the adoption of ASU 2014-09, ASU 2016-08, ASU 2016-10 and ASU 2016-12 will have on its condensed consolidated financial statements. Based on its assessment to date, the Company does expect that the adoption of this new accounting standard will impact the timing and amount of assets, liabilities, revenue and/or expenses recorded and the financial statement disclosures related to the Company’s revenue from contracts with its customers. For example, the treatment of extended payment terms, contingent revenue elements, commissions and costs to obtain customer contracts may change under the new accounting standard. The Company plans to adopt the new accounting standard as of January 1, 2019 using the modified retrospective approach and apply the guidance to contracts not completed as of that date. The cumulative effect of adoption will be recorded as an adjustment to the opening balance of retained earnings as of the adoption date. The Company continues to assess the impact of this new accounting standard on its business processes, accounting systems and internal controls. This assessment is subject to change, and the Company may identify other impacts on its condensed consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases (“ASU 2016-02”), which will require lessees to recognize most leases on their balance sheets as a right-of-use asset with a corresponding lease liability, and lessors to recognize a net lease investment. Additional qualitative and quantitative disclosures will also be required. This guidance is effective for public companies for annual reporting periods beginning after December 15, 2018 and for interim periods within those fiscal years. This guidance is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual reporting periods beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early application is permitted. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842: Leases (“ASU 2018-10”), which affects narrow aspects of the guidance issued in the amendments in ASU 2016-02. ASU 2018-10 has the same effective dates and transition requirements as ASU 2016-02. Additionally, in July 2018, the FASB issued update ASU 2018-11, Leases (Topic 842), Targeted Improvements (“ASU 2018-11”), which provided for an additional (and optional) transition method with which to adopt the new lease standard in ASU 2016-02. The additional method allows entities to apply the new leases standard at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company is currently assessing the potential impact that the adoption of ASU 2016-02, ASU 2018-10 and ASU 2018-11 will have on its condensed consolidated financial statements.

In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). This guidance requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions and reasonable and supportable forecasts that affect the collectibility. This guidance is effective for public companies for annual reporting periods beginning after December 15, 2019 and for interim periods within those fiscal years. This guidance is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual reporting periods beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. The Company is currently assessing the potential impact that the adoption of ASU 2016-13 will have on its condensed consolidated financial statements.

In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”), to address diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The standard is effective for public companies for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. The standard is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual periods beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019. The Company is currently assessing the potential impact that the adoption of ASU 2016-15 will have on its condensed consolidated financial statements.

In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfer of Assets Other than Inventory (“ASU 2016-16”), which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. The standard is effective for public companies for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. The standard is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual periods beginning after December 15, 2018, and interim reporting periods within annual periods beginning after December 15, 2019. The Company is currently assessing the potential impact that the adoption of ASU 2016-16 will have on its condensed consolidated financial statements.

In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging—Targeted Improvements to Accounting for Hedging Activities (“ASU 2017-12”), which aims to improve the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements. The standard is effective for public companies for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. The standard is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual periods beginning after December 15, 2019, and interim reporting periods within annual periods beginning after December 15, 2020. The Company is currently assessing the potential impact that the adoption of ASU 2017-12 will have on its condensed consolidated financial statements.

In June 2018, the FASB issued ASU 2018-07, Compensation – Stock Compensation (Topic 718) (“ASU 2018-07”), which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The amendments specify that Topic 718 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. The standard is effective for public companies for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. The standard is effective for private companies, and emerging growth companies that choose to take advantage of the extended transition periods, for annual periods beginning after December 15, 2019, and interim reporting periods within annual periods beginning after December 15, 2020. Early adoption is permitted, but no earlier than an entity’s adoption date of Topic 606. The Company is currently assessing the potential impact that the adoption of ASU 2018-07 will have on its condensed consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (“ASU 2018-13”), which modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurement, regarding transfers between levels of financial instruments, amounts of unrealized gains and losses included in other comprehensive income for Level 3 fair value measurements and the information used to determine the fair value of Level 3 fair value measurements. The standard is effective for both public companies and emerging growth companies that chose to take advantage of the extended transition periods, for annual periods beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. The Company is currently assessing the potential impact that the adoption of ASU 2018-13 will have on its condensed consolidated financial statements.

Inventory

9 Months Ended

Sep. 30, 2018

Inventory Disclosure [Abstract]

Inventory

3. Inventory

Inventory as of September 30, 2018 and December 31, 2017 consisted of the following:

	September 30, 2018			December 31, 2017
Raw materials	$	4,646		$	5,135
Work in process		17			7
Finished goods:
Manufactured finished goods		40,660			36,321
Deferred inventory costs		1,375			3,344
		46,698			44,807
Valuation adjustment for excess and obsolete inventory		(5,465	)		(8,659	)
	$	41,233		$	36,148

Property and Equipment

9 Months Ended

Sep. 30, 2018

Property Plant And Equipment [Abstract]

Property and Equipment

4. Property and Equipment

Property and equipment as of September 30, 2018 and December 31, 2017 consisted of the following:

	September 30, 2018			December 31, 2017
Computers and purchased software	$	15,138		$	12,343
Leasehold improvements		1,322			1,268
Furniture and fixtures		1,915			1,752
Machinery and equipment		20,578			17,911
Land		3,091			3,091
Building		4,765			4,765
Building improvements		5,189			4,906
Trial systems at customers’ sites		7,507			7,458
		59,505			53,494
Less: Accumulated depreciation and amortization		(29,864	)		(24,131	)
	$	29,641		$	29,363

During the nine months ended September 30, 2018 and 2017, the Company transferred trial systems from inventory into property and equipment with values of $50 and $960, respectively, net of transfers of trial systems to cost of revenue. In addition, the Company transferred $279 and $1,666 of equipment from inventory into property and equipment during the nine months ended September 30, 2018 and 2017, respectively.

Total depreciation and amortization expense was $2,369 and $2,007 for the three months ended September 30, 2018 and 2017, respectively, and $7,037 and $5,576 for the nine months ended September 30, 2018 and 2017, respectively.

Accrued Expenses and Other Current Liabilities

9 Months Ended

Sep. 30, 2018

Payables And Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

5. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities as of September 30, 2018 and December 31, 2017 consisted of the following:

	September 30, 2018		December 31, 2017
Accrued compensation and related taxes	$	18,696	$	22,465
Accrued warranty		777		1,246
Dividends and equitable adjustments payable (see Note 10)		4,189		10,661
Accrued customer incentives		4,749		8,437
Other accrued expenses		6,453		5,441
	$	34,864	$	48,250

Accrued Warranty

Substantially all of the Company’s products are covered by warranties for software and hardware for periods ranging from 90 days to one year. In addition, in conjunction with customers’ renewals of maintenance and support contracts, the Company offers an extended warranty for periods typically of one to three years for agreed-upon fees. In the event of a failure of a hardware product or software covered by these warranties, the Company must repair or replace the software or hardware or, if those remedies are insufficient, and at the discretion of the Company, provide a refund. The Company’s warranty reserve, which is included in accrued expenses and other current liabilities in the condensed consolidated balance sheets, reflects estimated material, labor and other costs related to potential or actual software and hardware warranty claims for which the Company expects to incur an obligation. The Company’s estimates of anticipated rates of warranty claims and the costs associated therewith are primarily based on historical information and future forecasts. The Company periodically assesses the adequacy of the warranty reserve and adjusts the amount as necessary. If the historical data used to calculate the adequacy of the warranty reserve are not indicative of future requirements, additional or reduced warranty reserves may be required.

A summary of changes in the amount reserved for warranty costs for the nine months ended September 30, 2018 and 2017 is as follows:

	Nine Months Ended September 30,
	2018			2017
Warranty reserve at beginning of period	$	1,246		$	1,256
Provisions		990			1,448
Charges		(1,459	)		(1,403	)
Warranty reserve at end of period	$	777		$	1,301

Fair Value Measurements

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

6. Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the price that would be received for an asset or the exit price that would be paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Level 1—	Quoted prices in active markets for identical assets and liabilities.

Level 2—	Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities at the measurement date; quoted prices in markets that are not active for identical or similar assets and liabilities; or other inputs that are observable or can be corroborated by observable market data.

Level 3—	Unobservable inputs that involve management judgment and are supported by little or no market activity, including pricing models, discounted cash flow methodologies and similar techniques.

The following tables present information about the fair value of the Company’s financial assets and liabilities as of September 30, 2018 and December 31, 2017 and indicate the level of the fair value hierarchy utilized to determine such fair values:

	Fair Value Measurements as of September 30, 2018 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Certificates of deposit	$	—	$	20,160	$	—	$	20,160
Certificates of deposit—restricted cash		—		1,012		—		1,012
Commercial paper		—		51,377		—		51,377
Money market mutual funds		226,724		—		—		226,724
Foreign currency forward contracts		—		74		—		74
	$	226,724	$	72,623	$	—	$	299,347
Liabilities:
SARs	$	—	$	—	$	1,699	$	1,699
Foreign currency forward contracts		—		85		—		85
	$	—	$	85	$	1,699	$	1,784

	Fair Value Measurements as of December 31, 2017 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Certificates of deposit	$	—	$	18,905	$	—	$	18,905
Commercial paper		—		11,483		—		11,483
Money market mutual funds		224,555		—		—		224,555
	$	224,555	$	30,388	$	—	$	254,943
Liabilities:
SARs	$	—	$	—	$	2,155	$	2,155
Foreign currency forward contracts		—		150		—		150
	$	—	$	150	$	2,155	$	2,305

During the nine months ended September 30, 2018 and 2017, there were no transfers between Level 1, Level 2 and Level 3.

There were no changes to the valuation techniques used to measure asset and liability fair values on a recurring basis during the nine months ended September 30, 2018 from those included in the Company’s audited consolidated financial statements for the year ended December 31, 2017. The following table provides a summary of changes in the fair values of the Company’s SARs liability, for which fair value is determined by Level 3 inputs:

	Nine Months Ended September 30,
	2018			2017
Fair value at beginning of period	$	2,155		$	1,195
Change in fair value		(456	)		(128	)
Exercises		—			—
Fair value at end of period	$	1,699		$	1,067

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Derivative Instruments	9 Months Ended
Derivative Instruments	Sep. 30, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative Instruments	7. Derivative Instruments The Company has certain international customers that are billed in foreign currencies. To mitigate the volatility related to fluctuations in the foreign exchange rates for accounts receivable denominated in foreign currencies, the Company enters into foreign currency forward contracts. As of September 30, 2018, the Company had foreign currency forward contracts outstanding with notional amounts totaling 19,399 Euros maturing in the fourth quarter of 2018 and first and second quarters of 2019. As of December 31, 2017, the Company had foreign currency forward contracts outstanding with notional amounts totaling 5,924 Euros maturing in the first and second quarters of 2018. The Company’s foreign currency forward contracts economically hedge certain risk but are not designated as hedges for financial reporting purposes, and accordingly, all changes in the fair value of these derivative instruments are recorded as unrealized foreign currency transaction gains or losses and are included in the condensed consolidated statements of operations and comprehensive income as a component of other income (expense). The Company records all derivative instruments in the condensed consolidated balance sheet at their fair values. As of September 30, 2018, the Company recorded an asset of $74 and as of September 30, 2018 and December 31, 2017, the Company recorded a liability of $85 and $150, respectively, related to outstanding foreign currency forward contracts, which were included in prepaid expenses and other current assets and in accrued expenses and other current liabilities, respectively, in the condensed consolidated balance sheets.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The Company’s effective income tax rate was 5.0% and 33.6% for the three months ended September 30, 2018 and 2017, respectively, and (10.3)% and 17.1% for the nine months ended September 30, 2018 and 2017, respectively. The effective income tax rate is based on the estimated annual effective tax rate, adjusted for discrete tax items recorded in the period. The provision for (benefit from) income taxes was $995 and $12,288 for the three months ended September 30, 2018 and 2017, respectively, and $(5,406) and $12,334 for the nine months ended September 30, 2018 and 2017, respectively. The Company determines its estimated annual effective tax rate at the end of each interim period based on estimated pre-tax income and facts known at that time. The estimated annual effective tax rate is applied to the year-to-date pre-tax income at the end of each interim period with certain adjustments. The tax effects of significant unusual or extraordinary items are reflected as discrete adjustments in the periods in which they occur. The Company’s estimated annual effective tax rate can change based on the mix of jurisdictional pre-tax income and other factors. The effective income tax rate for the three and nine months ended September 30, 2018 and 2017 differed from the federal statutory rate due to the foreign tax rate differential, permanent differences, research and development tax credits, excess tax benefit from stock-based transactions, state taxes and impacts of the legislation commonly referred to as the Tax Cuts and Jobs Act (the “TCJA”). Permanent differences primarily included the nondeductible stock-based compensation expense. The change in the provision for (benefit from) income taxes for the three and nine months ended September 30, 2018 compared to the three and nine months ended September 30, 2017 was primarily due to an increase in tax benefits from stock-based transactions. As of December 31, 2017, the Company has accounted for the impacts of the TCJA to the extent a reasonable estimate could be made and recognized provisional amounts related to the deemed repatriation tax, offset by the remeasurement of deferred tax assets and liabilities to record the effects of the tax law change in the period of enactment. This treatment is provided for in Staff Accounting Bulletin 118, which allows a company to record a provisional amount when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law during the measurement period. The measurement period ends when the company has obtained, prepared, and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. During the first quarter of 2018, the Internal Revenue Service issued additional guidance providing clarification on certain aspects of the deemed repatriation tax calculation. The additional guidance did not result in an adjustment to the provisional amounts recorded as of December 31, 2017. The Company will continue to monitor for new guidance related to provisional amounts recorded.

Debt

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Debt

9. Debt

The aggregate principal amount of debt outstanding as of September 30, 2018 and December 31, 2017 consisted of the following:

	September 30,		December 31,
	2018		2017
Term loans	$	294,750	$	297,000
Mortgage loan		7,035		7,261
Total principal amount of debt outstanding	$	301,785	$	304,261

Current and non-current debt obligations reflected in the condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 consisted of the following:

	September 30,			December 31,
	2018			2017
Current liabilities:
Term loans	$	3,000		$	3,000
Mortgage loan		311			303
Current portion of principal payment obligations		3,311			3,303
Unamortized debt issuance costs, current portion		(1,138	)		(1,147	)
Current portion of long-term debt, net of unamortized debt issuance costs	$	2,173		$	2,156
Non-current liabilities:
Term loans	$	291,750		$	294,000
Mortgage loan		6,724			6,958
Non-current portion of principal payment obligations		298,474			300,958
Unamortized debt issuance costs, non-current portion		(4,650	)		(5,499	)
Long-term debt, net of current portion and unamortized debt issuance costs	$	293,824		$	295,459

Term Loan and Revolving Credit Facilities

On December 20, 2016, the Company entered into a credit agreement with JPMorgan Chase Bank, N.A., as administrative agent, various lenders and JPMorgan Chase Bank, N.A. and Barclays Bank PLC providing for (i) a term loan facility of $300,000 and (ii) a revolving credit facility of up to $25,000 in revolving credit loans and letters of credit.

As of September 30, 2018 and December 31, 2017, $294,750 and $297,000 in principal amount, respectively, was outstanding under the term loan facility (the “Term Loans”) and the Company did not have any outstanding borrowings under the revolving credit facility; however, as of December 31, 2017, the Company had used $1,000 under the revolving credit facility for a stand-by letter of credit that served as collateral for a stand-by letter of credit issued by Bank of America to one of the Company’s customers pursuant to a contractual performance guarantee. As of September 30, 2018, the stand-by letter of credit that served as collateral was terminated, and the Company did not use any amount under the revolving credit facility. In addition, the Company may, subject to certain conditions, including the consent of the administrative agent and the institutions providing such increases, increase the facilities by an unlimited amount so long as the Company is in compliance with specified leverage ratios, or otherwise by up to $70,000.

Borrowings under the facilities bear interest at a floating rate, which can be either a Eurodollar rate plus an applicable margin or, at the Company’s option, a base rate (defined as the highest of (x) the JPMorgan Chase, N.A. prime rate, (y) the federal funds effective rate, plus one-half percent (0.50%) per annum and (z) a one-month Eurodollar rate plus 1.00% per annum) plus an applicable margin. The applicable margin for borrowings under the term loan facility is 4.00% per annum for Eurodollar rate loans (subject to a 1.00% per annum interest rate floor) and 3.00% per annum for base rate loans. As a result of the completion of the Company’s IPO in December 2017, the applicable margin for borrowings under the revolving credit facility is 1.75% per annum for Eurodollar rate loans and 0.75% per annum for base rate loans, subject to reduction based on the Company’s maintaining of specified net leverage ratios. The interest rates payable under the facilities are subject to an increase of 2.00% per annum during the continuance of any payment default.

For Eurodollar rate loans, the Company may select interest periods of one, two, three or six months or, with the consent of all relevant affected lenders, twelve months. Interest will be payable at the end of the selected interest period, but no less frequently than every three months within the selected interest period. Interest on any base rate loan is not set for any specified period and is payable quarterly. The Company has the right to convert Eurodollar rate loans into base rate loans and the right to convert base rate loans into Eurodollar rate loans at its option, subject, in the case of Eurodollar rate loans, to prepayment penalties if the conversion is effected prior to the end of the applicable interest period. As of September 30, 2018, the interest rate on the Term Loans was 6.24% per annum, which was based on a one-month Eurodollar rate of 2.24% per annum plus the applicable margin of 4.00% per annum for Eurodollar rate loans. As of December 31, 2017, the interest rate on the Term Loans was 5.69% per annum, which was based on a three-month Eurodollar rate of 1.69% per annum plus the applicable margin of 4.00% per annum for Eurodollar rate loans.

Upon entering into the term loan facility, the Company incurred debt issuance costs of $7,811, which were initially recorded as a reduction of the debt liability and are amortized to interest expense using the effective interest method from the issuance date of the Term Loan until the maturity date. Principal payments of $750 were made under the term loan facility during each of the three months ended September 30, 2018 and 2017, and $2,250 of principal payments were made during each of the nine months ended September 30, 2018 and 2017. Interest expense, including the amortization of debt issuance costs, totaled $4,881 and $4,328 for the three months ended September 30, 2018 and 2017, respectively, and totaled $14,114 and $12,443 for the nine months ended September 30, 2018 and 2017, respectively.

The revolving credit facility also requires payment of quarterly commitment fees at a rate of 0.25% per annum on the difference between committed amounts and amounts actually borrowed under the facility and customary letter of credit fees. For each of the three months ended September 30, 2018 and 2017, interest expense related to the fee for the unused amount of the revolving credit facility totaled $16 and $15, respectively. Interest expense related to the fee for the unused amount of the revolving credit facility for each of the nine months ended September 30, 2018 and 2017 totaled $46 and $45, respectively.

The Term Loans mature on December 20, 2023, and the revolving credit facility matures on December 20, 2021. The Term Loans are subject to amortization in equal quarterly installments, which commenced on March 31, 2017, of principal in an annual aggregate amount equal to 1.0% of the original principal amount of the Term Loans of $300,000, with the remaining outstanding balance payable at the date of maturity.

Voluntary prepayments of principal amounts outstanding under the term loan facility are permitted at any time; however, if a prepayment of principal is made with respect to a Eurodollar loan on a date other than the last day of the applicable interest period, the Company is required to compensate the lenders for any funding losses and expenses incurred as a result of the prepayment. Prior to the revolving credit facility maturity date, funds borrowed under the revolving credit facility may be borrowed, repaid and reborrowed, without premium or penalty.

In addition, the Company is required to make mandatory prepayments under the facilities with respect to (i) 100% of the net cash proceeds from certain asset dispositions (including casualty and condemnation events) by the Company or certain of its subsidiaries, subject to certain exceptions and reinvestment provisions, (ii) 100% of the net cash proceeds from the issuance or incurrence of any additional debt by the Company or certain of its subsidiaries, subject to certain exceptions, and (iii) 50% of the Company’s excess cash flow, as defined in the credit agreement, subject to reduction upon its achievement of specified performance targets.

The facilities are secured by, among other things, a first priority security interest, subject to permitted liens, in substantially all of the Company’s assets and all of the assets of certain of its subsidiaries and a pledge of certain of the stock of certain of its subsidiaries, in each case subject to specified exceptions. The facilities contain customary affirmative and negative covenants, including certain restrictions on the Company’s ability to pay dividends, and, with respect to the revolving credit facility, a financial covenant requiring the Company to maintain a specified total net leverage ratio in the event that on the last day of any fiscal quarter the Company has utilized more than 30% of its borrowing capacity under the facility. As of September 30, 2018 and December 31, 2017, the Company had not utilized more than 30% of its borrowing capacity under the revolving credit facility and compliance with the financial covenant was not applicable.

Commercial Mortgage Loan

On July 1, 2015, the Company entered into a commercial mortgage loan agreement in the amount of $7,950 (the “Mortgage Loan”). Borrowings under the Mortgage Loan bear interest at a rate of 3.5% per annum and are repayable in 60 monthly installments of $46, consisting of principal and interest based on a 20-year amortization schedule. The remaining amount of unpaid principal under the Mortgage Loan is due on the maturity date of July 1, 2020. Upon entering into the Mortgage Loan, the Company incurred debt issuance costs of $45, which was initially recorded as a direct deduction from the debt liability and are amortized to interest expense using the effective interest method from issuance date of the loan until the maturity date.

The Company made principal payments under the Mortgage Loan of $76 and $73 during the three months ended September 30, 2018 and 2017, respectively, and $226 and $218 during the nine months ended September 30, 2018 and 2017, respectively. Interest expense, including the amortization of debt issuance costs, totaled $66 and $68 for the three months ended September 30, 2018 and 2017, respectively, and $196 and $204 during the nine months ended September 30, 2018 and 2017, respectively.

The Mortgage Loan is secured by the land and building purchased in March 2015 and subjects the Company to various affirmative, negative and financial covenants, including maintenance of a minimum debt service ratio. The Company was in compliance with all covenants of the Mortgage Loan as of September 30, 2018 and December 31, 2017.

As of September 30, 2018, aggregate minimum future principal payments of the Company’s debt are summarized as follows:

Year Ending December 31,
2018	$	827
2019		3,314
2020		9,644
2021		3,000
2022		3,000
Thereafter		282,000
	$	301,785

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Special Dividends to Holders of Common and Preferred Stock November 2017 Special Dividend On November 30, 2017, the board of directors declared a special dividend to the holders of common stock and preferred stock of record on that date, contingent upon the closing of the Company’s IPO. The cash dividend declared to stockholders was $0.5802 per share of common stock, $5.8020 per share of Series B convertible preferred stock (the “Series B Preferred Stock”) and $5.8020 per share of Series C convertible preferred stock (the “Series C Preferred Stock”). Related to this special dividend declared in November 2017, the Company paid $865 of dividends to the common and preferred stockholders during the nine months ended September 30, 2018, and as of December 31, 2017, dividend payments to be made totaled $865 and were included in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheet. No dividend payments with respect to this special dividend were payable as of September 30, 2018. In connection with this special dividend declared in November 2017, the board of directors also approved, contingent upon the payment of the November 2017 special dividend, cash payments to be made to holders of the Company’s stock options, SARs and RSUs as an equitable adjustment to the holders of such instruments in accordance with the provisions of the Company’s equity incentive plans. The equitable adjustment payments to the holders of the stock options, SARs and RSUs are equal to $0.5802 per share multiplied by the net number of shares subject to outstanding equity awards after applying the treasury stock method. The cash payments to such holders will be made as their equity awards vest through fiscal year 2021. During the nine months ended September 30, 2018, the Company paid $996 to the holders of such vested equity awards. As of September 30, 2018 and December 31, 2017, equitable adjustment payments to be made as equity awards vest through fiscal year 2021, net of estimated forfeitures, totaled $739 and $1,735, respectively, and were included in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheets. The cash dividends declared to the holders of common stock, Series B Preferred Stock and Series C Preferred Stock totaled $19,572, $1,039 and $22,391, respectively, and the equitable adjustment to the holders of stock options, SARs and RSUs, net of estimated forfeitures, totaled $6,928. The $49,930 aggregate amount of such dividends and equitable adjustments was recorded as a charge to additional paid-in capital during the year ended December 31, 2017. May 2017 Special Dividend On May 10, 2017, the board of directors declared and the stockholders approved a special dividend to the holders of common stock and preferred stock of record on that date. The cash dividend declared to stockholders was $1.1774 per share of common stock, $11.7744 per share of Series B Preferred Stock and $11.7744 per share of Series C Preferred Stock. Related to this special dividend declared in May 2017, the Company paid $87,133 of dividends to the common and preferred stockholders during the nine months ended September 30, 2017. No dividend payments with respect to this special dividend were payable as of September 30, 2018 and December 31, 2017. In connection with the special dividend declared in May 2017, the board of directors also approved cash payments to be made to holders of the Company’s stock options, SARs and RSUs as an equitable adjustment to the holders of such instruments in accordance with the provisions of the Company’s equity incentive plans. The equitable adjustment payments to the holders of the stock options, SARs and RSUs are equal to $1.1774 per share multiplied by the net number of shares subject to outstanding equity awards after applying the treasury stock method. The cash payments to such holders will be made as their equity awards vest through fiscal year 2021. During the nine months ended September 30, 2018 and 2017, the Company paid $1,303 and $10,136 to the holders of such vested equity awards. As of September 30, 2018 and December 31, 2017, equitable adjustment payments to be made as equity awards vest through fiscal year 2021, net of estimated forfeitures, totaled $989 and $2,292, respectively, and were included in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheets. The cash dividends declared to the holders of common stock, Series B Preferred Stock and Series C Preferred Stock totaled $39,585, $2,108 and $45,440, respectively, and the equitable adjustment to the holders of stock options, SARs and RSUs, net of estimated forfeitures, totaled $12,723. The $99,856 aggregate amount of such dividends and equitable adjustments was recorded as a charge to additional paid-in capital (until reduced to zero) and a charge to accumulated deficit during the year ended December 31, 2017. December 2016 Special Dividend On December 21, 2016, the board of directors declared, and on December 29, 2016, the stockholders approved, a special dividend to the holders of common stock and preferred stock of record on December 27, 2016. The cash dividend declared to stockholders was $2.3306 per share of common stock, $23.3058 per share of Series B Preferred Stock and $23.3058 per share of Series C Preferred Stock. Related to this special dividend declared in December 2016, the Company paid $77,153 of dividends to the common and preferred stockholders during the nine months ended September 30, 2017 and no dividend payments with respect to this special dividend were payable as of September 30, 2018 and December 31, 2017. In connection with the special dividend declared in December 2016, the board of directors also approved cash payments to be made to holders of the Company’s stock options, SARs and RSUs as an equitable adjustment to the holders of such instruments in accordance with the provisions of the Company’s equity incentive plans. The equitable adjustment payments to the holders of stock options, SARs and RSUs are equal to $2.3306 per share multiplied by the net number of shares subject to outstanding equity awards after applying the treasury stock method. The cash payments to such holders will be made as their equity awards vest through fiscal year 2020. During the nine months ended September 30, 2018 and 2017, the Company paid $2,672 and $22,731 to the holders of such vested equity awards, respectively. As of September 30, 2018 and December 31, 2017, equitable adjustment payments to be made as equity awards vest through fiscal year 2020, net of estimated forfeitures, totaled $2,054 and $4,726, respectively, and were included in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheet. June 2016 Special Dividend On June 17, 2016, the board of directors declared and the stockholders approved a special dividend to the holders of common stock and preferred stock of record on that date. The cash dividend declared to stockholders was $0.5891 per share of common stock, $5.8910 per share of Series B Preferred Stock, and $5.8910 per share of Series C Preferred Stock. Related to this special dividend declared in June 2016, the Company paid no dividends to the common and preferred stockholders during the nine months ended September 30, 2018 and 2017, and, as of September 30, 2018 and December 31, 2017, no dividend payments with respect to this special dividend were payable. In connection with the special dividend declared in June 2016, the board of directors also approved cash payments to be made to holders of the Company’s stock options, SARs and RSUs as an equitable adjustment to the holders of such instruments in accordance with the provisions of the Company’s equity incentive plans. The equitable adjustment payments to the holders of stock options, SARs and RSUs are equal to $0.5891 per share multiplied by the net number of shares subject to outstanding equity awards after applying the treasury stock method. The cash payments to such holders will be made as their equity awards vest through fiscal year 2020. During the nine months ended September 30, 2018 and 2017, the Company paid $597 and $940, respectively, to the holders of such vested equity awards. As of September 30, 2018 and December 31, 2017, equitable adjustment payments to be made as equity awards vest through fiscal year 2020, net of estimated forfeitures, totaled $383 and $980 and were included in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheet. November 2014 Special Dividend On November 30, 2014, the board of directors declared and the stockholders approved a special dividend to the holders of common stock and preferred stock of record on that date. The cash dividend declared to stockholders was $0.3835 per share of common stock, $3.8346 per share of Series B Preferred Stock and $3.8346 per share of Series C Preferred Stock. Related to this special dividend declared in November 2014, the Company paid no dividends to the common and preferred stockholders during the nine months ended September 30, 2018 and 2017, and, as of September 30, 2018 and December 31, 2017, no dividend payments with respect to this special dividend were payable. In connection with the special dividend declared in November 2014, the board of directors also approved cash payments to be made to holders of the Company’s stock options and SARs as an equitable adjustment to the holders of such instruments in accordance with the provisions of the Company’s equity incentive plans. The equitable adjustment payments to the holders of stock options and SARs are equal to $0.3835 per share multiplied by the net number of shares subject to outstanding equity awards after applying the treasury stock method. The cash payments to the holders of stock options and SARs will be made as equity awards vest through fiscal year 2018. During the nine months ended September 30, 2018 and 2017, the Company paid $39 and $94, respectively, to the holders of stock options and SARs for vested equity awards. As of September 30, 2018 and December 31, 2017, equitable adjustment payments to be made as equity awards vest through fiscal year 2018, net of estimated forfeitures, totaled $24 and $63, respectively, and were included in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheets. Stock Repurchase Program On August 14, 2018, the Company announced a stock repurchase program authorizing it to repurchase up to $75,000 of the Company’s common stock. During the nine months ended September 30, 2018, the Company repurchased and retired 3,090 shares for $45,637, before commissions. As of September 30, 2018, $29,363 remained authorized for repurchases of the Company’s common stock under the stock repurchase program, and was used to repurchase and retire shares subsequent to September 30, 2018.

Stock-based Compensation

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

11. Stock-based Compensation

2017 Stock Incentive Plan

The Company’s 2017 Stock Incentive Plan (the “2017 Plan”) provides for the Company to sell or issue common stock or restricted common stock, or to grant qualified incentive stock options, nonqualified stock options, SARs, RSUs or other stock-based awards to the Company’s employees, officers, directors, advisers and outside consultants. The total number of shares authorized for issuance under the 2017 Plan was 10,129 shares as of September 30, 2018, of which 8,495 shares remained available for future grant.

Stock Options

The following table summarizes the outstanding stock option activity and a summary of information related to stock options as of and for the nine months ended September 30, 2018:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding at January 1, 2018		15,579		$	4.55		6.18	$	205,717
Granted		666			21.88
Exercised		(6,394	)		2.19
Forfeited		(143	)		10.68
Outstanding at September 30, 2018		9,708		$	7.21		6.57	$	77,921
Options exercisable at September 30, 2018		6,618		$	4.58		5.72	$	67,279
Vested or expected to vest at September 30, 2018		9,534		$	7.08		6.53	$	77,521

The fair value of each option is estimated on the date of grant using the Black-Scholes option-pricing model using the following assumptions:

Three Months Ended September 30,

Nine Months Ended September 30,

2018

2017

2018

2017

Risk-free interest rate

3.0%

2.0%–2.1%

2.7%–3.0%

2.0%–2.1%

Expected term (in years)

6.1–6.2

6.0–6.2

Expected volatility

30.6%–31.3%

33.9%–35.7%