Earnings Per Share - Schedule of Computations of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to HCA Holdings, Inc.	$ 920	$ 618	$ 658	$ 694	$ 582	$ 449	$ 507	$ 591	$ 2,890	$ 2,129	$ 1,875
Weighted average common shares outstanding									383,591	414,193	435,668
Effect of dilutive incremental shares									12,260	12,528	14,684
Shares used for diluted earnings per share									395,851	426,721	450,352
Basic earnings per share	$ 2.46	$ 1.63	$ 1.70	$ 1.75	$ 1.44	$ 1.08	$ 1.22	$ 1.41	$ 7.53	$ 5.14	$ 4.30
Diluted earnings per share	$ 2.39	$ 1.59	$ 1.65	$ 1.69	$ 1.40	$ 1.05	$ 1.18	$ 1.36	$ 7.30	$ 4.99	$ 4.16