Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) State Hospital Surgery_Center	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) State Hospital Surgery_Center	Jun. 30, 2016 USD ($)
Accounting Policies [Abstract]
Entity information, former legal or registered name			HCA Holdings, Inc.
Number of owned and operated hospitals | Hospital	172		172
Number of freestanding surgery centers | Surgery_Center	119		119
Number of facilities locations | State	20		20
General and administrative expense | $	$ 92	$ 93	$ 182	$ 178