CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 1,196,467	$ 836,033	$ 661,058
Operating expenses:
Platform operations	221,554	178,812	156,180
Sales and marketing	249,298	174,742	132,882
Technology and development	226,137	166,654	116,752
General and administrative	374,661	171,617	143,048
Total operating expenses	1,071,650	691,825	548,862
Income from operations	124,817	144,208	112,196
Other expense (income):
Interest expense (income), net	1,030	(656)	(4,719)
Foreign currency exchange loss, net	1,751	961	695
Total other expense (income), net	2,781	305	(4,024)
Income before income taxes	122,036	143,903	116,220
Provision for (benefit from) income taxes	(15,726)	(98,414)	7,902
Net income	$ 137,762	$ 242,317	$ 108,318
Earnings per share:
Basic	$ 0.29	$ 0.52	$ 0.24
Diluted	$ 0.28	$ 0.49	$ 0.23
Weighted-average shares outstanding:
Basic	476,851	462,865	445,329
Diluted	498,540	489,881	478,061