Earnings Per Share - Schedule of Computations of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income attributable to HCA Holdings, Inc.	$ 518	$ 365	$ 1,348	$ 1,132
Weighted average common shares outstanding	432,617	447,329	437,832	446,125
Effect of dilutive incremental shares	14,643	16,240	14,706	16,926
Shares used for diluted earnings per share	447,260	463,569	452,538	463,051
Basic earnings per share	$ 1.20	$ 0.82	$ 3.08	$ 2.54
Diluted earnings per share	$ 1.16	$ 0.79	$ 2.98	$ 2.44