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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to HCA Healthcare, Inc.	$ 657	$ 658	$ 1,316	$ 1,352
Weighted average common shares outstanding	365,847	386,406	368,056	391,401
Effect of dilutive incremental shares	9,491	12,253	9,591	13,216
Shares used for diluted earnings per share	375,338	398,659	377,647	404,617
Basic earnings per share	$ 1.79	$ 1.70	$ 3.58	$ 3.45
Diluted earnings per share	$ 1.75	$ 1.65	$ 3.48	$ 3.34