Aggregate Net Purchase Price Allocation to Assets and Liabilities based on Estimated Fair Values (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill	$ 3,596,114	$ 3,291,213	$ 3,049,016
2015 Acquisitions of Assets and Businesses
Business Acquisition [Line Items]
Working capital, net	(7,000)
Property & equipment	116,000
Goodwill	319,000
Other assets	128,000
Income tax assets, net of deferred tax liabilities	(22,000)
Cash paid for acquisitions	$ 534,000
2014 Acquisitions of Assets and Businesses
Business Acquisition [Line Items]
Working capital, net		(41,000)
Property & equipment		174,000
Goodwill		250,000
Other assets		59,000
Income tax assets, net of deferred tax liabilities		4,000
Debt		(16,000)
Other		1,000
Cash paid for acquisitions		$ 431,000