Segment Information - Segment Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenue	$ 1,784,401	$ 1,109,435	$ 1,421,374	$ 1,784,401
Segment EBITDA		371,839	481,099	586,505
Marketing Services
Segment Reporting Information [Line Items]
Revenue	1,659,786	979,611	1,292,795	1,659,786
Segment EBITDA		358,804	468,934	593,432
SaaS
Segment Reporting Information [Line Items]
Revenue	$ 124,615	129,824	128,579	124,615
Segment EBITDA		$ 13,035	$ 12,165	$ (6,927)