Assets Acquired and Liabilities Assumed and Recognized at Acquisition Dates at Estimated Fair Values (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 9,382,996	$ 9,294,479	$ 9,415,295
The Everett Clinic Medical Group (TEC)
Business Acquisition [Line Items]
Current assets, net of cash acquired	91,591
Property and equipment	108,533
Amortizable intangible and other long-term assets	34,050
Goodwill	244,502
Current liabilities assumed	(50,940)
Deferred income taxes	(16,880)
Noncontrolling interests assumed	(9,885)
Aggregate purchase price	$ 400,971