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								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 1,071	$ 612	$ 783	$ 1,039	$ 1,064	$ 759	$ 820	$ 1,144	$ 3,505	$ 3,787	$ 2,216
Weighted average common shares outstanding									341,210	347,297	362,305
Effect of dilutive incremental shares									7,016	8,006	9,916
Shares used for diluted earnings per share									348,226	355,303	372,221
Basic earnings per share	$ 3.16	$ 1.80	$ 2.29	$ 3.03	$ 3.09	$ 2.20	$ 2.35	$ 3.26	$ 10.27	$ 10.90	$ 6.12
Diluted earnings per share	$ 3.09	$ 1.76	$ 2.25	$ 2.97	$ 3.01	$ 2.15	$ 2.31	$ 3.18	$ 10.07	$ 10.66	$ 5.95