Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Costs and expenses:
Cost of services and product development	$ 1,550,568	$ 1,468,800	$ 1,320,198
Selling, general and administrative	2,103,424	1,884,141	1,599,004
Acquisition and integration charges	9,463	107,197	158,450
Operating income (loss)	370,087	259,715	(6,329)
Interest expense and other, net	(92,273)	(124,041)	(121,488)
(Loss) gain from divested operations	(2,075)	45,447	0
Provision (benefit) for income taxes	42,449	58,665	(131,096)
Net income	233,290	122,456	3,279
Operating Segments
Costs and expenses:
Operating income (loss)	2,711,927	2,518,973	2,000,386
Corporate and Reconciling Items
Costs and expenses:
Cost of services and product development	17,174	12,319	9,090
Selling, general and administrative	2,103,424	1,884,141	1,599,004
Depreciation and amortization	211,779	255,601	240,171
Acquisition and integration charges	9,463	107,197	158,450
Operating income (loss)	$ (2,341,840)	$ (2,259,258)	$ (2,006,715)