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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 11,562	$ 10,696	$ 10,733	$ 10,623	$ 10,641	$ 10,270	$ 10,319	$ 10,260	$ 43,614	$ 41,490	$ 39,678
Net income	641	530	795	777	1,085	745	791	811	2,743	3,432	2,696
Net income attributable to HCA Healthcare, Inc.	$ 474	$ 426	$ 657	$ 659	$ 920	$ 618	$ 658	$ 694	$ 2,216	$ 2,890	$ 2,129
Basic earnings per share	$ 1.34	$ 1.18	$ 1.79	$ 1.78	$ 2.46	$ 1.63	$ 1.70	$ 1.75	$ 6.12	$ 7.53	$ 5.14
Diluted earnings per share	$ 1.30	$ 1.15	$ 1.75	$ 1.74	$ 2.39	$ 1.59	$ 1.65	$ 1.69	$ 5.95	$ 7.30	$ 4.99