Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (52,250)	$ (47,515)	$ (19,634)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	19,671	13,693	10,207
Amortization of deferred costs	7,982	5,472	5,947
Accretion of interest on debt	5,711	4,616	493
Loss on extinguishment of convertible notes	1,406
Provision for doubtful accounts and sales return reserve	661	252	637
Stock-based compensation	33,489	25,589	9,218
Change in fair value of contingent consideration obligation	(550)	(250)	(1,020)
Other non-cash adjustments	(132)	(261)	(236)
Change in operating assets and liabilities:
Accounts receivable	(25,558)	(2,623)	(13,067)
Prepaid expenses	(3,481)	(1,952)	(551)
Deferred costs	(15,293)	(8,285)	(89)
Other assets	1,758	(4,014)	(6,643)
Accounts payable	5,312	(1,263)	(90)
Accrued payroll and employee related liabilities	4,548	4,686	3,596
Accrued expenses	(1,308)	298	(132)
Deferred revenue	29,704	13,164	16,378
Other liabilities	(1,353)	1,688	(151)
Net cash provided by operating activities	10,317	3,295	4,863
Cash flows from investing activities:
Capital expenditures	(5,269)	(1,721)	(1,667)
Proceeds from landlord reimbursement	1,143
Proceeds from sale leaseback transaction			794
Payments for acquisition of business, net of acquired cash	(58,419)	(35,857)	(21,235)
Additions to capitalized software development costs	(7,819)	(8,499)	(6,160)
Purchase of short-term investments	(1,975)	(87,204)	(60,764)
Maturities of short-term investments	47,765	85,069	18,060
Purchase of intangibles		(201)
Net cash used in investing activities	(24,574)	(48,413)	(70,972)
Cash flows from financing activities:
Proceeds from public offering, net of costs	139,110	(276)	9,572
Proceeds from issuance of convertible notes	450,000		115,000
Payments of debt issuance costs	(12,686)	(84)	(3,834)
Purchase of convertible notes capped call hedge	(44,910)		(12,922)
Repurchase of convertible notes	(57,791)
Proceeds from termination of convertible notes capped call hedge	5,780
Restricted stock units withheld to settle employee tax withholding liability	(4,602)	(7,925)
Payments of contingent consideration obligation		(431)	(3,750)
Proceeds from employee stock purchase plan	2,337	1,823	1,540
Proceeds from option exercises	17,411	10,150	2,869
Other	(548)	(158)
Net cash provided by financing activities	494,101	3,099	108,475
Effect of exchange rates on cash, cash equivalents and restricted cash	(250)	(964)	(80)
Net increase (decrease) in cash, cash equivalents and restricted cash	479,594	(42,983)	42,286
Cash, cash equivalents and restricted cash—beginning of year	60,068	103,051	60,765
Cash, cash equivalents and restricted cash—end of year	539,662	60,068	103,051
Supplemental disclosures of cash flow information:
Interest	1,766	1,634
Taxes, net of refunds received	90	113	28
Supplemental disclosure of non-cash activities
Capitalized assets included in accounts payable and accrued expenses	136	1,609	73
Capitalized development costs included in accounts payable and accrued expenses	71
Debt issuance costs included in accounts payable and other assets, net	131		84
Deferred offering costs in accounts payable and accrued expenses		21
Common stock issued in connection with acquisition	32,798
Stock-based compensation capitalized for software development	$ 500	236	$ 81
Note payable issued for asset acquisition		52
Note payable issued for business acquisition		$ 383