Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (35,252)	$ (13,932)	$ (31,895)
Adjustments to reconcile net loss to cash flows provided by operating activities:
Depreciation and amortization of property and equipment	8,486	7,970	11,961
Amortization of intangible assets	17,112	7,500	7,107
Stock-based compensation	25,657	19,768	21,699
Impairment of intangible assets	5,471	0	0
Deferred income taxes	(20,361)	1,088	752
Other	(1,340)	(1,265)	(784)
Changes in operating assets and liabilities:
Accounts receivable	(30,759)	(851)	11,369
Inventory	5,786	4,858	(1,001)
Other operating assets	269	506	4,915
Accounts payable	13,415	(821)	(1,257)
Accrued expenses and other long-term liabilities	(4,263)	(7,778)	(4,134)
Deferred revenue	23,859	2,149	1,137
Net cash provided by operating activities	8,080	19,192	19,869
Cash flows from investing activities:
Purchases of property and equipment	(3,999)	(4,626)	(7,792)
Business acquisitions, net of cash acquired	(42,951)	(20,669)	(10,897)
Purchases of marketable securities	(28,731)	(78,528)	(54,772)
Sale/maturities of marketable securities	96,112	75,178	67,980
Proceeds from the sale of intangible assets	576	1,298	896
Net cash provided by (used in) investing activities	21,007	(27,347)	(4,585)
Cash flows from financing activities:
Borrowings under revolving line of credit	15,500	0	0
Principal payments on revolving line of credit	(13,500)	0	0
Principal payments of capital lease obligations	(99)	(43)	(76)
Payment of debt issuance costs	(731)	0	0
Proceeds from the sale of common stock in connection with employee stock purchase plan	1,252	1,360	2,378
Proceeds from the exercise of stock options	617	153	1,757
Payment of tax withholding obligations related to net share settlements of restricted stock awards	(7,523)	(1,810)	(2,344)
Repurchase of common stock	0	(9,530)	(7,917)
Net cash used in financing activities	(4,484)	(9,870)	(6,202)
Effect of exchange rate changes on cash and cash equivalents	547	(163)	(128)
Net increase (decrease) in cash and cash equivalents	25,150	(18,188)	8,954
Cash and cash equivalents, beginning of year	31,923	50,111	41,157
Cash and cash equivalents, end of period	57,073	31,923	50,111
Supplemental disclosure of cash flow information:
Interest paid	317	41	64
Income taxes paid	2,290	1,249	1,430
Income tax refunds received	274	511	357
Supplemental disclosure of non-cash investing activities:
Capital expenditures incurred, but not yet paid	1,043	277	375
Property and equipment acquired under capital lease	0	36	137
Business acquisition purchase consideration - common stock issued	413,982	0	0
Business acquisition purchase consideration - note issued to selling equity holders	22,500	0	0
Supplemental disclosure of non-cash financing activities:
Total fair value of restricted stock awards, restricted stock units, performance-based stock awards and performance-based stock units on date vested	$ 20,515	$ 10,376	$ 9,138