Goodwill and Intangible Assets - Carrying Amounts of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 1,482,982
Divestitures			(46,129)
Write-off of fully amortized intangible assets			(6,929)
Foreign currency translation impact and other			(17,821)
Gross cost, ending balance	$ 1,412,103		1,412,103
Accumulated amortization	(326,367)		(326,367)		$ (190,960)
Finite-lived intangible assets, net	1,085,736		1,085,736		1,292,022
Amortization of intangibles	50,852	$ 51,224	152,625	$ 123,014
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			1,200,316
Divestitures			(45,175)
Write-off of fully amortized intangible assets			(303)
Foreign currency translation impact and other			(13,682)
Gross cost, ending balance	1,141,156		1,141,156
Accumulated amortization	(162,029)		(162,029)		(92,983)
Finite-lived intangible assets, net	979,127		$ 979,127		1,107,333
Customer Relationships | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			4 years
Customer Relationships | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			13 years
Software
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 123,424
Divestitures			(321)
Write-off of fully amortized intangible assets			(2,625)
Foreign currency translation impact and other			(385)
Gross cost, ending balance	120,093		120,093
Accumulated amortization	(42,461)		(42,461)		(26,344)
Finite-lived intangible assets, net	77,632		$ 77,632		97,080
Software | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			3 years
Software | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			7 years
Content
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 104,313
Divestitures			(473)
Write-off of fully amortized intangible assets			(669)
Foreign currency translation impact and other			(4,082)
Gross cost, ending balance	99,089		99,089
Accumulated amortization	(91,275)		(91,275)		(47,475)
Finite-lived intangible assets, net	7,814		$ 7,814		56,838
Content | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			1 year 6 months
Content | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			5 years
Other
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 54,929
Divestitures			(160)
Write-off of fully amortized intangible assets			(3,332)
Foreign currency translation impact and other			328
Gross cost, ending balance	51,765		51,765
Accumulated amortization	(30,602)		(30,602)		(24,158)
Finite-lived intangible assets, net	$ 21,163		$ 21,163		$ 30,771
Other | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			2 years
Other | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			5 years