Earnings Per Share - Schedule of Computations of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Line Items]
Net income attributable to HCA Holdings, Inc	$ 314	$ 360	$ 391	$ 540	$ 1,935	$ 61	$ 229	$ 240	$ 1,605	$ 2,465	$ 1,207
Weighted average common shares outstanding									440,178	476,609	426,424
Effect of dilutive incremental shares									19,225	19,334	10,923
Shares used for diluted earnings per share									459,403	495,943	437,347
Basic earnings per share	$ 0.71	$ 0.82	$ 0.89	$ 1.23	$ 4.43	$ 0.12	$ 0.44	$ 0.54	$ 3.65	$ 5.17	$ 2.83
Diluted earnings per share	$ 0.68	$ 0.78	$ 0.85	$ 1.18	$ 4.25	$ 0.11	$ 0.43	$ 0.52	$ 3.49	$ 4.97	$ 2.76