Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (26,197)	$ (29,260)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	7,700	6,328
Amortization of deferred costs	3,607	2,513
Loss on disposal of assets		84
Deferred income taxes	83	101
Accretion of interest on convertible senior notes	2,424	2,274
Non-cash investment income	(245)	(228)
Provision for doubtful accounts and sales reserve	389	24
Change in fair value of contingent consideration		(250)
Stock-based compensation	15,793	16,512
Changes in operating assets and liabilities:
Accounts receivable	(1,387)	5,627
Prepaid expenses	(3,461)	(2,011)
Deferred costs	(4,398)	(4,198)
Other assets	83	(1,005)
Accounts payable	3,669	93
Accrued payroll and employee related liabilities	(2,864)	305
Accrued expenses	(719)	566
Deferred revenue	1,523	1,061
Other liabilities	511	12
Net cash used in operating activities	(3,489)	(1,452)
Cash flows from investing activities:
Capital expenditures	(3,875)	(414)
Proceeds from landlord reimbursement	1,143
Payments for acquisition of business, net of acquired cash	(6,764)	(35,857)
Purchase of short-term investments	(1,975)	(30,932)
Maturities of short-term investments	44,265	70,645
Additions to intangibles		(168)
Additions to capitalized software development costs	(3,949)	(4,038)
Net cash provided by (used in) investing activities	28,845	(764)
Cash flows from financing activities:
Restricted stock units withheld to settle employee tax withholding liability	(449)	(3,772)
Payment of contingent consideration		(431)
Payment on note payable	(427)
Payments on finance lease obligation	(121)
Proceeds from public offering, net of costs	139,110
Payments of debt issuance costs		(84)
Proceeds from employee stock purchase plan	1,283	881
Proceeds from stock option exercises	13,487	5,835
Net cash provided by financing activities	152,883	2,429
Effect of exchange rates on cash, cash equivalents and restricted cash	(52)	(665)
Net increase (decrease) in cash, cash equivalents and restricted cash	178,187	(452)
Cash, cash equivalents and restricted cash—beginning of period	60,068	103,051
Cash, cash equivalents and restricted cash—end of period	238,255	102,599
Supplemental disclosures of cash flow information:
Interest	863	771
Taxes, net of refunds received		41
Supplemental disclosure of non-cash activities:
Capitalized assets included in accounts payable and accrued expenses	217	85
Capitalized development costs included in accounts payable and accrued expenses	14
Stock-based compensation capitalized for software development	$ 338	$ 204