Summary of Changes in Carrying Amount of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 3,049,016		$ 3,036,765
Goodwill acquired during the period	250,212	[1]
Adjustments to goodwill	(8,015)		12,251	[1]
Goodwill, Ending Balance	3,291,213		3,049,016
Acute Care Services
Goodwill [Line Items]
Goodwill, Beginning Balance	383,011		382,696
Goodwill acquired during the period	4,088	[1]
Adjustments to goodwill	0		315	[1]
Goodwill, Ending Balance	387,099		383,011
Behavioral Health Services
Goodwill [Line Items]
Goodwill, Beginning Balance	2,666,005		2,654,069
Goodwill acquired during the period	246,124	[1]
Adjustments to goodwill	(8,015)		11,936	[1]
Goodwill, Ending Balance	$ 2,904,114		$ 2,666,005

[1] The increase in the Behavioral Health Services' goodwill consists primarily of an amount that was reclassified from other assets.