Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (93,396)	$ (52,250)	$ (47,515)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	30,759	19,671	13,693
Amortization of deferred costs	12,609	7,982	5,472
Deferred income taxes	(3,478)	109	125
Accretion of interest on debt	22,161	5,711	4,616
Loss on extinguishment of convertible notes	446	1,406
Provision for credit losses and sales reserve	3,071	661	252
Stock-based compensation	46,755	33,489	25,589
Change in fair value of contingent consideration obligation	3,665	(550)	(250)
Other non-cash adjustments	78	(241)	(386)
Change in operating assets and liabilities:
Accounts receivable	(22,614)	(25,558)	(2,623)
Prepaid expenses	(3,983)	(3,481)	(1,952)
Deferred costs	(18,902)	(15,293)	(8,285)
Other assets	146	1,758	(4,014)
Accounts payable	1,547	5,312	(1,263)
Accrued payroll and employee related liabilities	3,499	4,548	4,686
Accrued expenses	1,057	(1,308)	298
Deferred revenue	24,964	29,704	13,164
Other liabilities	7,419	(1,353)	1,688
Net cash provided by operating activities	15,803	10,317	3,295
Cash flows from investing activities:
Capital expenditures	(3,257)	(5,269)	(1,721)
Proceeds from landlord reimbursement		1,143
Payments for acquisition of business, net of acquired cash	(55,138)	(58,419)	(35,857)
Additions to capitalized software development costs	(9,651)	(7,819)	(8,499)
Purchase of short-term investments		(1,975)	(87,204)
Maturities of short-term investments		47,765	85,069
Purchase of intangibles	(17,139)		(201)
Net cash used in investing activities	(85,185)	(24,574)	(48,413)
Cash flows from financing activities:
Proceeds from public offering, net of costs		139,110	(276)
Proceeds from issuance of convertible notes		450,000
Payments of debt issuance costs		(12,686)	(84)
Purchase of convertible notes capped call hedge	(131)	(44,910)
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	(6,364)	(4,602)	(7,925)
Payments of contingent consideration obligation			(431)
Proceeds from employee stock purchase plan	3,389	2,337	1,823
Proceeds from option exercises	8,160	17,411	10,150
Other		(548)	(158)
Net cash provided by financing activities	5,054	494,101	3,099
Effect of exchange rates on cash, cash equivalents and restricted cash	296	(250)	(964)
Net increase (decrease) in cash, cash equivalents and restricted cash	(64,032)	479,594	(42,983)
Cash, cash equivalents and restricted cash—beginning of year	539,662	60,068	103,051
Cash, cash equivalents and restricted cash—end of year	475,630	539,662	60,068
Supplemental disclosures of cash flow information:
Interest	1,938	1,766	1,634
Taxes, net of refunds received	706	90	113
Supplemental disclosure of non-cash activities
Common stock issued in connection with acquisitions	53,193	32,798
Deferred consideration in connection with acquisition	4,044
Contingent consideration in connection with acquisitions	6,267	550
Common stock issued in connection with settlement of convertible notes	11,375
Capitalized assets included in accounts payable and accrued expenses	291	136	1,609
Stock-based compensation capitalized for software development	324	500	236
Other non-cash activities	$ (163)	$ 202	$ 456