Goodwill and Intangible Assets - Schedule of Finite-lived Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross	$ 1,052,792	$ 923,199
Accumulated Amortization	(963,500)	(891,422)
Effects of Foreign Currency Translation	(6,715)
Net	$ 82,577	$ 31,777	$ 147,480
Weighted Average Remaining Amortization Period in Years	2 years 4 months 24 days	2 years
Client relationships
Finite-Lived Intangible Assets [Line Items]
Gross	$ 803,642	$ 701,802
Accumulated Amortization	(748,460)	(701,518)
Effects of Foreign Currency Translation	(5,326)
Net	$ 49,856	$ 284	85,615
Weighted Average Remaining Amortization Period in Years	2 years 8 months 12 days	1 year 4 months 24 days
Trademarks and domain names
Finite-Lived Intangible Assets [Line Items]
Gross	$ 225,177	$ 200,300
Accumulated Amortization	(193,978)	(169,545)
Effects of Foreign Currency Translation	(1,389)
Net	$ 29,810	$ 30,755	60,533
Weighted Average Remaining Amortization Period in Years	1 year 10 months 24 days	2 years
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
Net	0	0	0
Covenants not to compete
Finite-Lived Intangible Assets [Line Items]
Gross	4,373	1,497
Accumulated Amortization	(1,462)	(759)
Effects of Foreign Currency Translation	0
Net	$ 2,911	$ 738	$ 1,332
Weighted Average Remaining Amortization Period in Years	2 years 7 months 6 days	1 year 9 months 18 days