Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount	$ 720,571		$ 699,667
Accumulated amortization	(498,486)		(457,730)
Net carrying amount	222,085		241,937
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount	343,489		344,883
Accumulated amortization	(239,718)		(220,434)
Net carrying amount	$ 103,771		124,449
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	$ 41,934		42,025
Accumulated amortization	(35,164)		(32,456)
Net carrying amount	$ 6,770		9,569
Trademarks | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	10 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	$ 278,609		256,220
Accumulated amortization	(185,911)		(169,974)
Net carrying amount	$ 92,698		$ 86,246
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	(37,693)		(34,866)
Net carrying amount	$ 18,846		$ 21,673