Quarterly Consolidated Financial Information - Schedule of Quarterly Consolidated Financial Information (Detail) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 10,641	$ 10,270	$ 10,319	$ 10,260	$ 10,249	$ 9,856	$ 9,897	$ 9,676	$ 41,490	$ 39,678	$ 36,918
Net income	1,085	745	791	811	738	573	665	720	3,432	2,696	2,373
Net income attributable to HCA Holdings, Inc.	$ 920	$ 618	$ 658	$ 694	$ 582	$ 449	$ 507	$ 591	$ 2,890	$ 2,129	$ 1,875
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