Goodwill and Intangible Assets - Carrying Amounts of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 1,392,861
Intangible assets fully amortized			(103,974)
Foreign currency translation impact			(3,652)
Gross cost, ending balance	$ 1,285,235		1,285,235
Accumulated amortization	(311,798)		(311,798)		$ (350,296)
Finite-lived intangible assets, net	973,437		973,437		1,042,565
Amortization of intangibles	32,164	$ 50,127	65,847	$ 101,773
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			1,131,656
Intangible assets fully amortized			0
Foreign currency translation impact			(3,573)
Gross cost, ending balance	1,128,083		1,128,083
Accumulated amortization	(232,450)		(232,450)		(184,918)
Finite-lived intangible assets, net	895,633		$ 895,633		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			(113)
Gross cost, ending balance	110,588		110,588
Accumulated amortization	(50,090)		(50,090)		(38,901)
Finite-lived intangible assets, net	60,498		$ 60,498		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			(85,900)
Foreign currency translation impact			(1)
Gross cost, ending balance	12,941		12,941
Accumulated amortization	(8,922)		(8,922)		(92,717)
Finite-lived intangible assets, net	4,019		$ 4,019		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			(18,074)
Foreign currency translation impact			35
Gross cost, ending balance	33,623		33,623
Accumulated amortization	(20,336)		(20,336)		(33,760)
Finite-lived intangible assets, net	$ 13,287		$ 13,287		$ 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