CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenue	$ 160,660	$ 120,987
Type of Revenue [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
Operating expenses:
Platform operations	$ 40,208	$ 33,651
Type of Cost, Good or Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
Sales and marketing	$ 34,294	$ 22,737
Technology and development	36,794	25,312
General and administrative	38,598	33,617
Total operating expenses	149,894	115,317
Income from operations	10,766	5,670
Other expense (income):
Interest income, net	(1,092)	(997)
Foreign currency exchange loss, net	1,234	1,330
Credit loss expense on available-for-sale securities	275
Total other expense, net	417	333
Income before income taxes	10,349	5,337
Benefit from income taxes	(13,708)	(4,814)
Net income	$ 24,057	$ 10,151
Earnings per share:
Basic	$ 0.53	$ 0.23
Diluted	$ 0.50	$ 0.21
Weighted average shares outstanding:
Basic	45,501	43,906
Diluted	48,313	47,314