Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Costs and expenses:
Cost of services and product development	$ 322,551		$ 387,999		$ 663,829	$ 734,644
Selling, general and administrative	494,840		514,976		991,479	1,033,746
Acquisition and integration charges (credits)	2,157		(358)		3,716	2,414
Operating income	99,651		116,002		224,370	164,801
Interest expense and other, net	(40,695)		(24,996)		(68,559)	(50,667)
Loss from divested operations	0		0		0	(2,075)
Less: Provision for income taxes	3,879		(12,400)		25,637	(12,142)
Net income	55,077	$ 75,097	103,406	$ 20,795	130,174	124,201
Reportable segments
Costs and expenses:
Operating income	654,936		687,103		$ 1,331,729	1,309,865
Reportable segments | Maximum
Costs and expenses:
Percent of target bonus allocated to segments					100.00%
Corporate and other expenses
Costs and expenses:
Cost of services and product development	4,352		4,220		$ 3,532	3,183
Selling, general and administrative	494,840		514,976		991,479	1,033,746
Depreciation and amortization	53,936		52,263		108,632	105,721
Acquisition and integration charges (credits)	2,157		(358)		3,716	2,414
Operating income	$ (555,285)		$ (571,101)		$ (1,107,359)	$ (1,145,064)