Goodwill and Intangible Assets - Carrying Amounts of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 1,279,386
Additions due to an acquisition			19,460
Intangible assets fully amortized			82,384
Foreign currency translation impact			8,121
Gross cost, ending balance	$ 1,224,583		1,224,583
Accumulated amortization	(449,104)		(449,104)		$ (472,388)
Finite-lived intangible assets, net	775,479		775,479		806,998
Amortization of intangibles	26,154	$ 31,208	56,668	$ 63,387
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			1,154,210
Additions due to an acquisition			7,980
Intangible assets fully amortized			17,788
Foreign currency translation impact			7,895
Gross cost, ending balance	1,152,297		1,152,297
Accumulated amortization	(414,460)		(414,460)		(381,776)
Finite-lived intangible assets, net	737,837		$ 737,837		772,434
Customer Relationships | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			6 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			$ 110,597
Additions due to an acquisition			11,200
Intangible assets fully amortized			60,631
Foreign currency translation impact			226
Gross cost, ending balance	61,392		61,392
Accumulated amortization	(30,394)		(30,394)		(83,320)
Finite-lived intangible assets, net	30,998		$ 30,998		27,277
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			$ 3,965
Additions due to an acquisition			0
Intangible assets fully amortized			3,965
Foreign currency translation impact			0
Gross cost, ending balance	0		0
Accumulated amortization	0		0		(3,595)
Finite-lived intangible assets, net	0		$ 0		370
Content | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			2 years
Content | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life			3 years
Other
Finite-lived Intangible Assets [Roll Forward]
Gross cost, beginning balance			$ 10,614
Additions due to an acquisition			280
Intangible assets fully amortized			0
Foreign currency translation impact			0
Gross cost, ending balance	10,894		10,894
Accumulated amortization	(4,250)		(4,250)		(3,697)
Finite-lived intangible assets, net	$ 6,644		$ 6,644		$ 6,917
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