Quarterly Results - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Mar. 31, 2012 Resulting from an agreement entered into with the United States Department of Health and Human Services, the Secretary of Health and Human Services, and the Centers for Medicare and Medicaid Services	Mar. 31, 2012 Oklahoma Supplemental Hospital Offset Payment Program	Jun. 30, 2012 Implementation of EHR applications	Mar. 31, 2012 Implementation of EHR applications	Mar. 31, 2012 Implementation of EHR applications Federal fiscal years 2006 through 2009	Dec. 31, 2012 EHR applications	Sep. 30, 2012 EHR applications	Sep. 30, 2012 Write-off of deferred financing costs	Dec. 31, 2012 Sale of an acute care facility	Jun. 30, 2012 Reimbursements related to prior years	Dec. 31, 2012 Professional and general liability self-insurance reserves relating to years prior to 2012
Quarterly Financial Information [Line Items]
Favorable pre-tax reduction	$ 10.4	$ 30.2	$ 7.0				$ 8.9	$ 2.2		$ 26.4	$ 5.5	$ 27.2
Favorable after-tax reduction	6.4	18.8	4.3				5.5	1.3		16.4	3.4	15.5
Tax reduction per diluted share	$ 0.07	$ 0.19	$ 0.04	$ 0.05	$ 0.05		$ 0.06	$ 0.01	$ 0.19	$ 0.17	$ 0.03	$ 0.16
Unfavorable pre-tax reduction				8.0	8.3	2.4			29.2
Unfavorable after-tax reduction				5.0	5.1				18.1
Unfavorable after tax impact related to actute care hospital construction					$ 2.7