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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 1,064	$ 759	$ 820	$ 1,144	$ 474	$ 426	$ 657	$ 659	$ 3,787	$ 2,216	$ 2,890
Weighted average common shares outstanding									347,297	362,305	383,591
Effect of dilutive incremental shares									8,006	9,916	12,260
Shares used for diluted earnings per share									355,303	372,221	395,851
Basic earnings per share	$ 3.09	$ 2.20	$ 2.35	$ 3.26	$ 1.34	$ 1.18	$ 1.79	$ 1.78	$ 10.90	$ 6.12	$ 7.53
Diluted earnings per share	$ 3.01	$ 2.15	$ 2.31	$ 3.18	$ 1.30	$ 1.15	$ 1.75	$ 1.74	$ 10.66	$ 5.95	$ 7.30