Business Combinations - Assets Acquired and Liabilities Assumed - HST (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 4,363,070	$ 4,257,336	$ 4,142,013
Measurement period adjustments
Total consideration transferred in cash	(182)
Cash and cash equivalents	64
Trade accounts receivable, net	(112)
Prepaid expenses	0
Operating lease right-of-use assets	0
Property and equipment, net	0
Other current assets, net	1,635
Accounts payable	(139)
Other accrued expenses	(140)
Deferred income taxes	1,016
Operating lease obligation	0
Total identifiable net assets	2,324
Goodwill	(2,506)
Trademarks
Measurement period adjustments
Intangibles	0
Technology
Measurement period adjustments
Intangibles	0
Client relationships
Measurement period adjustments
Intangibles	0
HST
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Total consideration transferred in cash	145,234	145,416
Cash and cash equivalents	5,448	5,384
Trade accounts receivable, net	773	885
Prepaid expenses	138	138
Operating lease right-of-use assets	1,306	1,306
Property and equipment, net	78	78
Other current assets, net	1,695	60
Accounts payable	(558)	(419)
Other accrued expenses	(450)	(310)
Deferred income taxes	(6,838)	(7,854)
Operating lease obligation	(1,415)	(1,415)
Total identifiable net assets	32,417	30,093
Goodwill	112,817	115,323
HST | Trademarks
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangibles	1,430	1,430
HST | Technology
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangibles	6,350	6,350
HST | Client relationships
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangibles	$ 24,460	$ 24,460