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, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 581	$ 1,039
Weighted average common shares outstanding	338,242	342,876
Effect of dilutive incremental shares	5,854	7,440
Shares used for diluted earnings per share	344,096	350,316
Basic earnings	$ 1.72	$ 3.03
Diluted earnings	$ 1.69	$ 2.97