BASIS OF PRESENTATION (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Description of Business
Number of acute care hospitals operated by subsidiaries	49
Number of licensed beds in hospitals operated by subsidiaries	13,180
Number of free-standing and provider-based outpatient centers operated by subsidiaries	122
Minimum number of hospitals to which business process solutions is provided by Conifer	600
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	$ 2,594	$ 2,491
Gross Carrying Amount	1,117		1,076
Accumulated Amortization	(447)		(426)
Net Book Value	670		650
Cash Equivalents
Cash and cash equivalents	95	104	364	113
Book overdrafts classified as accounts payable	198		232
Cash and cash equivalents related to captive insurance subsidiaries	78		65
Accrued property and equipment purchases for items received but not yet paid	51		98
Accrued property and equipment purchases, for items received but not yet paid, included in accounts payable	39		93
Non-cancellable capital leases primarily for equipment	31	17
Capitalized software costs
Summary of significant accounting policies
Gross Carrying Amount	950		927
Accumulated Amortization	(418)		(399)
Net Book Value	532		528
Long-term debt issuance costs
Summary of significant accounting policies
Gross Carrying Amount	109		106
Accumulated Amortization	(25)		(25)
Net Book Value	84		81
Other
Summary of significant accounting policies
Gross Carrying Amount	58		43
Accumulated Amortization	(4)		(2)
Net Book Value	54		41
Medicare
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	540	629
Medicaid
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	188	177
Managed care
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	1,361	1,326
Indemnity, self-pay and other
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	260	241
Acute care hospitals - other revenue
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	28	24
Other operations
Summary of significant accounting policies
Net operating revenues before provision for doubtful accounts	$ 217	$ 94