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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 668	$ 612	$ 2,328	$ 2,434
Weighted average common shares outstanding	338,168	340,789	338,057	341,932
Effect of dilutive incremental shares	5,178	6,698	4,957	6,780
Shares used for diluted earnings per share	343,346	347,487	343,014	348,712
Basic earnings	$ 1.97	$ 1.80	$ 6.89	$ 7.12
Diluted earnings	$ 1.95	$ 1.76	$ 6.79	$ 6.98