CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Revenue	$ 219,811	$ 160,660
Type of Revenue [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
Operating expenses:
Platform operations	$ 50,500	$ 40,208
Type of Cost, Good or Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
Sales and marketing	$ 55,764	$ 34,294
Technology and development	53,918	36,794
General and administrative	51,845	38,598
Total operating expenses	212,027	149,894
Income from operations	7,784	10,766
Other expense (income):
Interest expense (income), net	45	(817)
Foreign currency exchange loss (gain), net	(353)	1,234
Total other expense (income), net	(308)	417
Income before income taxes	8,092	10,349
Benefit from income taxes	(14,550)	(13,708)
Net income	$ 22,642	$ 24,057
Earnings per share:
Basic	$ 0.48	$ 0.53
Diluted	$ 0.45	$ 0.50
Weighted average shares outstanding:
Basic	47,282	45,501
Diluted	49,792	48,313