Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Costs and expenses:
Cost of services and product development	$ 1,345,024	$ 1,550,568	$ 1,468,800
Selling, general and administrative	2,038,963	2,103,424	1,884,141
Acquisition and integration charges	6,282	9,463	107,197
Operating income	490,150	370,087	259,715
Interest expense and other, net	(119,203)	(92,273)	(124,041)
(Loss) gain from divested operations	0	(2,075)	45,447
Provision for income taxes	59,388	42,449	58,665
Net income	$ 266,745	233,290	122,456
Maximum
Costs and expenses:
Percent of target bonus charges allocated to segments	100.00%
Operating Segments
Costs and expenses:
Operating income	$ 2,770,898	2,711,927	2,518,973
Corporate and Reconciling Items
Costs and expenses:
Cost of services and product development	16,519	17,174	12,319
Selling, general and administrative	2,038,963	2,103,424	1,884,141
Depreciation and amortization	218,984	211,779	255,601
Acquisition and integration charges	6,282	9,463	107,197
Operating income	$ (2,280,748)	$ (2,341,840)	$ (2,259,258)