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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 2,269	$ 668	$ 5,142	$ 2,328
Weighted average common shares outstanding	318,072	338,168	328,048	338,057
Effect of dilutive incremental shares	5,957	5,178	5,200	4,957
Shares used for diluted earnings per share	324,029	343,346	333,248	343,014
Basic earnings per share	$ 7.13	$ 1.97	$ 15.67	$ 6.89
Diluted earnings per share	$ 7.00	$ 1.95	$ 15.43	$ 6.79