Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Summary of Restatement Adjustments to Financial Statements (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	$ 759	$ 426	$ 2,723	$ 1,742
Net cash provided by operating activities				3,692
HCA Healthcare, Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	759	426	2,723	1,742
Net cash provided by operating activities				74
HCA Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	(708)	(524)	(2,016)	(1,463)
Net cash provided by operating activities				(1,694)
Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	1,253	904	4,079	2,769
Net cash provided by operating activities				3,766
Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	183	56	607	396
Net cash provided by operating activities				1,546
Eliminations [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	$ (728)	(436)	$ (2,670)	(1,702)
As Previously Reported [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		426		1,742
Net cash provided by operating activities				3,692
As Previously Reported [Member] | HCA Healthcare, Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		426		1,742
Net cash provided by operating activities				74
As Previously Reported [Member] | HCA Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		(524)		(1,463)
Net cash provided by operating activities				(1,694)
As Previously Reported [Member] | Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		787		2,467
Net cash provided by operating activities				3,342
As Previously Reported [Member] | Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		173		698
Net cash provided by operating activities				1,970
As Previously Reported [Member] | Eliminations [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		(436)		(1,702)
Adjustment [Member] | Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		117		302
Net cash provided by operating activities				424
Adjustment [Member] | Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		$ (117)		(302)
Net cash provided by operating activities				$ (424)