Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 469,624	$ 366,620	$ 291,609
Costs and expenses:
Cost of revenue	156,880	106,268	78,878
Sales and marketing	165,421	149,773	156,814
General and administrative	76,757	60,557	56,967
Product development	158,390	108,414	82,145
Restructuring costs	3,397	29,420	2,043
Amortization of purchased intangibles	2,045	1,639	1,794
Total costs and expenses	562,890	456,071	378,641
Loss from operations	(93,266)	(89,451)	(87,032)
Other expense, net:
Interest expense, net	(37,406)	(14,334)	(7,407)
Other income (expense), net	3,294	(1,343)	1,213
Total other expense, net	(34,112)	(15,677)	(6,194)
Loss before (benefit from) provision for income taxes	(127,378)	(105,128)	(93,226)
(Benefit from) provision for income taxes	(2,404)	2,466	2,845
Net loss	$ (124,974)	$ (107,594)	$ (96,071)
Net loss per share of common stock:
Basic	$ (1.80)	$ (1.63)	$ (1.53)
Diluted	$ (1.80)	$ (1.63)	$ (1.53)
Weighted-average shares used to compute net loss income per share:
Basic	69,606,105	65,888,450	62,593,026
Diluted	69,606,105	65,888,450	62,593,026