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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 426	$ 618	$ 1,742	$ 1,970
Weighted average common shares outstanding	360,170	378,199	365,398	386,968
Effect of dilutive incremental shares	9,664	11,393	9,615	12,609
Shares used for diluted earnings per share	369,834	389,592	375,013	399,577
Basic earnings per share	$ 1.18	$ 1.63	$ 4.77	$ 5.09
Diluted earnings per share	$ 1.15	$ 1.59	$ 4.64	$ 4.93