Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (68,810)	$ (39,118)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	22,116	13,192
Amortization of deferred costs	9,152	5,486
Deferred income taxes	(2,310)	201
Accretion of interest on convertible senior notes	16,527	3,667
Provision for credit losses and sales reserve	1,442	642
Stock-based compensation	34,939	24,094
Change in fair value of contingent consideration obligation	1,500
Other non-cash adjustments	(37)	(248)
Changes in operating assets and liabilities:
Accounts receivable	(7,929)	(8,405)
Prepaid expenses	(4,752)	(5,144)
Deferred costs	(12,000)	(8,438)
Other assets	(3,248)	924
Accounts payable	2,286	7,318
Accrued payroll and employee related liabilities	3,965	1,974
Accrued expenses	(1)	(296)
Deferred revenue	1,107	12,373
Other liabilities	2,457	632
Net cash provided by (used in) operating activities	(3,596)	8,854
Cash flows from investing activities:
Capital expenditures	(2,122)	(4,417)
Proceeds from landlord reimbursement		1,143
Payments for acquisition of business, net of acquired cash	(54,757)	(58,419)
Additions to capitalized software development costs	(7,296)	(5,867)
Purchase of short-term investments		(1,975)
Maturities of short-term investments		47,765
Net cash used in investing activities	(64,175)	(21,770)
Cash flows from financing activities:
Proceeds from public offering, net of costs		139,110
Restricted stock units withheld to settle employee tax withholding liability	(4,269)	(4,531)
Proceeds from employee stock purchase plan	3,389	2,337
Proceeds from stock option exercises	6,764	15,822
Other	(131)	(548)
Net cash provided by financing activities	5,753	152,190
Effect of exchange rates on cash, cash equivalents and restricted cash	(411)	(227)
Net increase (decrease) in cash, cash equivalents and restricted cash	(62,429)	139,047
Cash, cash equivalents and restricted cash—beginning of period	539,662	60,068	$ 60,068
Cash, cash equivalents and restricted cash—end of period	477,233	199,115	$ 539,662
Supplemental disclosures of cash flow information:
Interest	974	863
Taxes, net of refunds received	577
Supplemental disclosure of non-cash activities:
Common stock issued in connection with acquisitions	53,193	32,838
Acquisition-related deferred consideration	4,044
Contingent consideration in connection with acquisitions	6,267	550
Common stock issued in connection with settlement of convertible notes	938
Capitalized assets included in accounts payable and accrued expenses	86	122
Capitalized development costs included in accounts payable and accrued expenses		7
Purchase accounting payable, net	(15)
Stock-based compensation capitalized for software development costs	$ 243	$ 420