Goodwill and Intangible Assets - Schedule of Finite-lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross	$ 1,054,508	$ 1,052,792
Accumulated Amortization	(978,713)	(963,500)
Effects of Foreign Currency Translation	1,662	(6,715)
Net	$ 77,457	$ 82,577
Weighted Average Remaining Amortization Period in Years	2 years 2 months 12 days	2 years 4 months 24 days
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross	$ 805,095	$ 803,642
Accumulated Amortization	(757,153)	(748,460)
Effects of Foreign Currency Translation	1,259	(5,326)
Net	$ 49,201	$ 49,856
Weighted Average Remaining Amortization Period in Years	2 years 6 months	2 years 8 months 12 days
Trademarks and domain names
Finite-Lived Intangible Assets [Line Items]
Gross	$ 225,377	$ 225,177
Accumulated Amortization	(200,118)	(193,978)
Effects of Foreign Currency Translation	403	(1,389)
Net	$ 25,662	$ 29,810
Weighted Average Remaining Amortization Period in Years	1 year 8 months 12 days	1 year 10 months 24 days
Patented technologies
Finite-Lived Intangible Assets [Line Items]
Gross	$ 19,600	$ 19,600
Accumulated Amortization	(19,600)	(19,600)
Effects of Foreign Currency Translation	0	0
Net	$ 0	$ 0
Weighted Average Remaining Amortization Period in Years	0 years	0 years
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Gross	$ 4,436	$ 4,373
Accumulated Amortization	(1,842)	(1,462)
Effects of Foreign Currency Translation	0	0
Net	$ 2,594	$ 2,911
Weighted Average Remaining Amortization Period in Years	2 years 3 months 18 days	2 years 7 months 6 days