Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Costs and expenses:
Cost of services and product development - unallocated	$ 357,209	$ 237,609
Selling, general and administrative	487,745	304,244
Acquisition and integration charges	59,266	13,272
Operating (loss) income	(8,711)	53,514
Interest expense and other, net	34,160	5,017
(Benefit) provision for income taxes	(23,284)	12,064
Net (loss) income	(19,587)	36,433
Reportable segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	$ 614,814	388,617
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 - unallocated	$ 8,458	1,057
Selling, general and administrative	487,745	304,244
Depreciation and amortization	68,056	16,530
Acquisition and integration charges	$ 59,266	$ 13,272