PROPERTY AND PROFESSIONAL AND GENERAL LIABILITY INSURANCE (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Property Insurance April 1, 2010 through March 31, 2013	Mar. 31, 2013 Professional and General Liability Insurance	Dec. 31, 2012 Professional and General Liability Insurance	Mar. 31, 2013 Professional and General Liability Insurance June 1, 2012 through May 31, 2013
Insurance coverage
Insurance coverage limit			$ 600
Insurance coverage limit per occurrence excluding floods, earthquakes, and windstorms			600
Annual aggregate sub-limits for floods and earthquakes covered under insurance policies			100
Annual aggregate sub-limits for windstorms covered under insurance policies			0
Per-occurrence sub-limit for windstorms covered under insurance policies			100
Deductible for general claims (as a percent)			5.00%
General claims, maximum coverage			25
Deductible for other specific claims (as a percent)			2.00%
Other specific claims, maximum coverage			25
Other covered claims, minimum deductible			1
Self insurance reserve				347	356
Loss contingency, discount rate maturity (in years)				P7Y	P7Y
Risk-free rate (as a percent)				1.24%	1.18%
Self-insurance retention per occurrence						5
Insurance retention per occurrence						10
Insurance coverage, additional to aggregate self coverage						10
Aggregate self-insurance retentions per occurrence						15
Insurance coverage, percent reinsured						80.00%
Insurance coverage, percent retained						20.00%
Insurance coverage, maximum amount retained						2
Insurance coverage, additional to aggregate coverage						25
Insurance coverage, aggregate limit						175
Malpractice expense	$ 26	$ 28