Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Consolidated Balance Sheets [Abstract]
Allowance for doubtful patient accounts	$ 4,110	$ 3,504
Other current assets of hospitals held for sale	17	38
Accumulated amortization	903	827
Noncurrent assets of hospitals held for sale	41	90
Current liabilities of hospitals held for sale	$ 6	$ 10
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Common stock, par value per share	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	113,732,933	117,701,087
Common stock, shares outstanding	112,757,384	116,725,538
Treasury stock, shares	975,549	975,549