Aggregate Net Purchase Price Allocation to Assets and Liabilities based on Estimated Fair Values (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 3,844,628	$ 3,825,157	$ 3,784,106
2018 Acquisitions of Assets and Businesses
Business Acquisition [Line Items]
Working capital, net	(3,988)
Property & equipment	59,520
Goodwill	45,090
Other assets	8,409
Income tax assets, net of deferred tax liabilities	1,749
Other	(316)
Cash paid for acquisitions	$ 110,464
2016 Acquisitions of Assets and Businesses
Business Acquisition [Line Items]
Working capital, net			6,680
Property & equipment			343,846
Goodwill			234,658
Other assets			19,910
Income tax assets, net of deferred tax liabilities			11,551
Debt			(152)
Noncontrolling interest			(2,690)
Cash paid for acquisitions			$ 613,803