CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (11,357)	$ (2,674)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,417	4,532
Stock-based compensation	7,796	7,756
Amortization of debt discount and issuance cost	2,425
Loss on disposal of property and equipment	2
Allowance for doubtful accounts	95	(268)
Deferred income taxes	102	(97)
Change in fair value of escrowed shares and contingent consideration, net	7,350	(2,585)
Changes in operating assets and liabilities:
Accounts receivable	(4,433)	264
Prepaid expenses and other current assets	(1,634)	(1,295)
Accounts payable and other current liabilities	(5,783)	(1,749)
Accrued compensation and benefits	(5,901)	(4,843)
Deferred revenues	668	726
Net cash used in operating activities	(6,253)	(233)
Cash flows from investing activities:
Purchases of property and equipment	(1,713)	(1,637)
Purchases of short-term investments	(25,721)	(25,078)
Proceeds from maturities of short-term investment	34,750	50,116
Net cash provided by investing activities	7,316	23,401
Cash flows from financing activities:
Proceeds from issuances of common stock under stock plans	1,675	1,144
Payments for taxes related to net share settlement of equity awards	(6,857)
Principal payments on promissory note and capital lease obligations	(82)	(9)
Net cash provided by (used in) financing activities	(5,264)	1,135
Effect of exchange rates on cash and cash equivalents	13	9
Net increase (decrease) in cash and cash equivalents	(4,188)	24,312
Cash and cash equivalents at beginning of period	334,635	106,174
Cash and cash equivalents at end of period	330,447	130,486
Supplemental disclosures of cash flow information:
Cash paid for income taxes	42	24
Cash paid for interest	8
Supplemental disclosures of noncash investing and financing activities:
Fixed asset purchases not yet paid	$ 320	562
Computer equipment acquired under promissory note		819
Property and equipment acquired under capital lease		$ 31