Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 169,339	$ 120,912
Cost of revenue	52,658	41,295
Gross profit	116,681	79,617
Operating expenses:
Marketing	35,444	26,194
Product development	24,947	20,721
General and administrative	24,647	18,904
Total operating expenses	85,038	65,819
Income from operations	31,643	13,798
Other (expense) income:
Interest expense	(4,653)	(3,764)
Interest and other income	3,385	1,097
Foreign exchange gain	1,062	1,850
Total other expense	(206)	(817)
Income before income taxes	31,437	12,981
Benefit (provision) for income taxes	142	(14)
Net income	$ 31,579	$ 12,967
Net income per share attributable to common stockholders:
Basic (in dollars per share)	$ 0.26	$ 0.11
Diluted (in dollars per share)	$ 0.24	$ 0.10
Weighted-average common shares outstanding:
Basic (in shares)	119,679,149	121,267,092
Diluted (in shares)	130,237,875	125,772,315