Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 818,379	$ 603,693	$ 441,231
Cost of revenue	271,036	190,762	150,986
Gross profit	547,343	412,931	290,245
Operating expenses:
Marketing	215,570	158,013	109,085
Product development	121,878	97,249	74,616
General and administrative	121,134	82,883	91,486
Asset impairment charges	0	0	3,162
Total operating expenses	458,582	338,145	278,349
Income from operations	88,761	74,786	11,896
Other (expense) income:
Interest expense	(24,320)	(22,178)	(11,130)
Interest and other income	13,199	8,957	2,394
Foreign exchange gain (loss)	3,006	(6,487)	29,105
Total other (expense) income	(8,115)	(19,708)	20,369
Income before income taxes	80,646	55,078	32,265
Benefit for income taxes	15,248	22,413	49,535
Net income	$ 95,894	$ 77,491	$ 81,800
Net income per share attributable to common stockholders:
Basic (in dollars per share)	$ 0.80	$ 0.64	$ 0.69
Diluted (in dollars per share)	$ 0.76	$ 0.61	$ 0.68
Weighted average common shares outstanding:
Basic (in shares)	119,665,248	120,146,076	118,538,687
Diluted (in shares)	125,720,073	127,084,785	122,267,673