CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net revenue	$ 220,807	$ 262,474	$ 639,738	$ 745,371
Costs and expenses:
Cost of revenue (exclusive of depreciation and amortization shown separately below)	13,193	16,514	41,865	45,754
Sales and marketing	101,301	127,655	334,887	374,016
Product development	53,022	56,661	174,104	169,302
General and administrative	30,887	39,703	100,825	101,927
Depreciation and amortization	12,544	12,391	37,484	36,507
Restructuring	535	0	3,847	0
Total costs and expenses	211,482	252,924	693,012	727,506
Income (loss) from operations	9,325	9,550	(53,274)	17,865
Other income, net	399	3,063	3,277	11,645
Income (loss) before income taxes	9,724	12,613	(49,997)	29,510
Provision for (benefit from) income taxes	10,744	2,552	(9,484)	5,781
Net (loss) income attributable to common stockholders	$ (1,020)	$ 10,061	$ (40,513)	$ 23,729
Net (loss) income per share attributable to common stockholders
Basic (in USD per share)	$ (0.01)	$ 0.14	$ (0.56)	$ 0.31
Diluted (in USD per share)	$ (0.01)	$ 0.14	$ (0.56)	$ 0.30
Weighted-average shares used to compute net (loss) income per share attributable to common stockholders
Basic (in shares)	73,514	70,773	72,495	75,975
Diluted (in shares)	73,514	73,712	72,495	79,315