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 loss	$ (37,710)	$ (13,870)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	10,172	7,646
Amortization of deferred costs	3,928	4,140
Loss on disposal of assets	112	15
Deferred income taxes	101	62
Accretion of interest on convertible senior notes	3,435
Non-cash investment income	(308)	(74)
Provision for doubtful accounts and sales reserve	158	588
Change in fair value of contingent consideration	(250)
Stock-based compensation	20,007	4,838
Increase (decrease) in operating assets and liabilities:
Accounts receivable	1,524	(3,591)
Prepaid expenses	(2,439)	(1,552)
Deferred costs	(6,991)	216
Other assets	(1,584)	(5,336)
Accounts payable	(113)	820
Accrued payroll and employee related liabilities	2,109	2,263
Accrued expenses	(621)	(54)
Deferred revenue	7,237	7,801
Other liabilities	457	467
Net cash (used in) provided by operating activities	(776)	4,379
Cash flows from investing activities:
Capital expenditures	(855)	(1,337)
Proceeds from sale leaseback		794
Payments for acquisition of business, net of acquired cash	(35,857)	(21,235)
Purchase of short-term investments	(57,709)	(29,955)
Maturities of short-term investments	74,069	6,000
Additions to intangibles	(184)
Additions to capitalized software development costs	(6,722)	(4,586)
Net cash used in investing activities	(27,258)	(50,319)
Cash flows from financing activities:
Restricted stock units withheld to settle employee tax withholding liability	(7,921)
Principal payments on capital leases	(61)
Payment of contingent consideration	(431)	(3,750)
Payment on note payable	(59)
Proceeds from follow on offering, net		10,444
Payments of public offering costs		(872)
Payments of debt issuance costs	(84)	(40)
Proceeds from employee stock purchase plan	1,758	1,540
Proceeds from stock option exercises	8,821	2,087
Net cash provided by financing activities	2,023	9,409
Effect of exchange rates on cash and cash equivalents	(746)	(309)
Net decrease in cash, cash equivalents and restricted cash	(26,757)	(36,840)
Cash, cash equivalents and restricted cash—beginning of period	103,051	60,765
Cash, cash equivalents and restricted cash—end of period	76,294	23,925
Supplemental disclosures of cash flow information:
Interest	771
Taxes, net of refunds received	43	25
Supplemental disclosure of non-cash activities:
Capitalized assets included in accounts payable and accrued expenses	278	24
Debt issuance costs included in accounts payable and accrued expenses		100
Note payable issued for asset acquisition	52
Stock-based compensation capitalized for software development	$ 250	$ 34