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
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 1,423	$ 581
Weighted average common shares outstanding	338,123	338,242
Effect of dilutive incremental shares	5,198	5,854
Shares used for diluted earnings per share	343,321	344,096
Basic earnings per share	$ 4.21	$ 1.72
Diluted earnings per share	$ 4.14	$ 1.69