Goodwill and Intangible Assets - Carrying Amounts of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	$ 1,301,120	$ 1,392,861
Additions due to an acquisition		5,250
Intangible assets fully amortized	(33,262)	(107,258)
Foreign currency translation impact	11,528	10,267
Gross cost, ending balance	1,279,386	1,301,120
Accumulated amortization	(472,388)	(376,033)
Finite-lived intangible assets, net	806,998	925,087
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	1,145,109	1,131,656
Additions due to an acquisition		3,600
Intangible assets fully amortized	(2,394)	0
Foreign currency translation impact	11,495	9,853
Gross cost, ending balance	1,154,210	1,145,109
Accumulated amortization	(381,776)	(283,369)
Finite-lived intangible assets, net	$ 772,434	861,740
Customer Relationships | Minimum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	3 years
Customer Relationships | Maximum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	13 years
Software
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	$ 111,033	110,701
Additions due to an acquisition
Intangible assets fully amortized	(787)	0
Foreign currency translation impact	351	332
Gross cost, ending balance	110,597	111,033
Accumulated amortization	(83,320)	(61,564)
Finite-lived intangible assets, net	$ 27,277	49,469
Software | Minimum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	2 years
Software | Maximum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	7 years
Content
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	$ 14,140	98,842
Additions due to an acquisition		1,200
Intangible assets fully amortized	(9,929)	(85,900)
Foreign currency translation impact	(246)	(2)
Gross cost, ending balance	3,965	14,140
Accumulated amortization	(3,595)	(11,225)
Finite-lived intangible assets, net	$ 370	2,915
Content | Minimum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	2 years
Content | Maximum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	3 years
Other
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance	$ 30,838	51,662
Additions due to an acquisition		450
Intangible assets fully amortized	(20,152)	(21,358)
Foreign currency translation impact	(72)	84
Gross cost, ending balance	10,614	30,838
Accumulated amortization	(3,697)	(19,875)
Finite-lived intangible assets, net	$ 6,917	$ 10,963
Other | Minimum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	2 years
Other | Maximum
Finite-lived Intangible Assets [Roll Forward]
Remaining amortization period	11 years