Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount		$ 765,033	$ 731,761
Accumulated amortization		(540,348)	(511,852)
Net carrying amount		224,685	219,909
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount		358,524	343,981
Accumulated amortization		(259,325)	(246,088)
Net carrying amount		$ 99,199	97,893
Customer relationships | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	8 years	8 years
Customer relationships | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	14 years	14 years
Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount		$ 41,995	42,036
Accumulated amortization		(36,085)	(35,467)
Net carrying amount		$ 5,910	6,569
Trademarks | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	2 years	2 years
Trademarks | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	15 years	15 years
Software packages
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount		$ 307,975	289,205
Accumulated amortization		(204,419)	(191,662)
Net carrying amount		$ 103,556	97,543
Software packages | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	3 years	3 years
Software packages | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	10 years	10 years
Non-compete agreement
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	15 years	15 years
Gross amount		$ 56,539	56,539
Accumulated amortization		(40,519)	(38,635)
Net carrying amount		$ 16,020	$ 17,904