Goodwill and Intangible Assets - Carrying Amounts of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	$ 1,392,861
Intangible assets fully amortized	(85,894)
Foreign currency translation impact	8,683
Gross cost, ending balance	1,315,650
Accumulated amortization	(299,595)		$ (350,296)
Finite-lived intangible assets, net	1,016,055		1,042,565
Amortization of intangibles	33,683	$ 51,646
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	1,131,656
Intangible assets fully amortized	0
Foreign currency translation impact	8,344
Gross cost, ending balance	1,140,000
Accumulated amortization	(210,203)		(184,918)
Finite-lived intangible assets, net	$ 929,797		946,738
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	$ 110,701
Intangible assets fully amortized	0
Foreign currency translation impact	278
Gross cost, ending balance	110,979
Accumulated amortization	(44,632)		(38,901)
Finite-lived intangible assets, net	$ 66,347		71,800
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	$ 98,842
Intangible assets fully amortized	(85,894)
Foreign currency translation impact	0
Gross cost, ending balance	12,948
Accumulated amortization	(7,877)		(92,717)
Finite-lived intangible assets, net	$ 5,071		6,125
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	$ 51,662
Intangible assets fully amortized	0
Foreign currency translation impact	61
Gross cost, ending balance	51,723
Accumulated amortization	(36,883)		(33,760)
Finite-lived intangible assets, net	$ 14,840		$ 17,902
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	11 years