Aggregate Net Purchase Price Allocation to Assets and Liabilities based on Estimated Fair Values (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 3,882,715	$ 3,869,760	$ 3,844,628
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