Goodwill and Other Intangible Assets - Gross Carrying Amounts and Accumulated Amortization Relating to Other Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,628,241	$ 789,480
Accumulated Amortization	(227,849)	(170,970)
Net	1,400,392	618,510	$ 521,213
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,251,783	603,966
Accumulated Amortization	(199,741)	(150,350)
Net	1,052,042	453,616
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	369,512	180,416
Accumulated Amortization	(23,056)	(16,154)
Net	346,456	164,262
Non-competition agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,946	5,098
Accumulated Amortization	(5,052)	(4,466)
Net	$ 1,894	$ 632