Earnings Per Share - Schedule of Computations of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 3,754	$ 3,505	$ 3,787
Weighted average common shares outstanding	338,274	341,210	347,297
Effect of dilutive incremental shares	5,331	7,016	8,006
Shares used for diluted earnings per share	343,605	348,226	355,303
Basic earnings per share	$ 11.10	$ 10.27	$ 10.90
Diluted earnings per share	$ 10.93	$ 10.07	$ 10.66