Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Condensed Consolidated Balance Sheets [Abstract]
Allowance for doubtful patient accounts	$ 4,051	$ 4,110
Other current assets of hospitals held for sale	5	17
Noncurrent assets of hospitals held for sale	25	41
Current liabilities of hospitals held for sale	$ 2	$ 6
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	114,731,736	113,732,933
Common stock, shares outstanding	113,756,187	112,757,384
Treasury stock, shares	975,549	975,549