Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (44,605)	$ (26,197)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	13,976	7,700
Amortization of deferred costs	5,735	3,607
Deferred income taxes	(3,014)	83
Accretion of interest on convertible senior notes	10,949	2,424
Provision for credit losses and sales reserve	1,387	389
Stock-based compensation	21,588	15,793
Other non-cash adjustments		(245)
Changes in operating assets and liabilities:
Accounts receivable	3,341	(1,387)
Prepaid expenses	(3,265)	(3,461)
Deferred costs	(6,943)	(4,398)
Other assets	(3,429)	83
Accounts payable	2,164	3,669
Accrued payroll and employee related liabilities	(334)	(2,864)
Accrued expenses	(593)	(719)
Deferred revenue	(2,722)	1,523
Other liabilities	2,696	511
Net cash used in operating activities	(3,069)	(3,489)
Cash flows from investing activities:
Capital expenditures	(1,175)	(3,875)
Proceeds from landlord reimbursement		1,143
Payments for acquisition of business, net of acquired cash	(44,265)	(6,764)
Additions to capitalized software development costs	(4,673)	(3,949)
Purchase of short-term investments		(1,975)
Maturities of short-term investments		44,265
Net cash provided by (used in) investing activities	(50,113)	28,845
Cash flows from financing activities:
Proceeds from public offering, net of costs		139,110
Restricted stock units withheld to settle employee tax withholding liability	(927)	(449)
Proceeds from employee stock purchase plan	1,710	1,283
Proceeds from stock option exercises	4,585	13,487
Other	(131)	(548)
Net cash provided by financing activities	5,237	152,883
Effect of exchange rates on cash, cash equivalents and restricted cash	(419)	(52)
Net increase (decrease) in cash, cash equivalents and restricted cash	(48,364)	178,187
Cash, cash equivalents and restricted cash—beginning of period	539,662	60,068	$ 60,068
Cash, cash equivalents and restricted cash—end of period	491,298	238,255	$ 539,662
Supplemental disclosures of cash flow information:
Interest	974	863
Taxes, net of refunds received	476
Supplemental disclosure of non-cash activities:
Capitalized assets included in accounts payable and accrued expenses	373	217
Capitalized development costs included in accounts payable and accrued expenses	3	14
Common stock issued in connection with acquisitions	35,508
Acquisition-related deferred common stock consideration	895
Contingent consideration in connection with acquisitions	4,220
Purchase accounting payable, net	619
Stock-based compensation capitalized for software development	$ 152	$ 338