Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Summary of Restatement Adjustments to Financial Statements (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	$ 820	$ 657	$ 1,964	$ 1,316
Net cash provided by operating activities				2,684
HCA Healthcare, Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	820	657	1,964	1,316
Net cash provided by operating activities				357
HCA Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	(666)	(476)	(1,308)	(939)
Net cash provided by operating activities				(1,112)
Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	1,284	966	2,826	1,865
Net cash provided by operating activities				2,469
Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	234	168	424	340
Net cash provided by operating activities				970
Eliminations [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.	$ (852)	(658)	$ (1,942)	(1,266)
As Previously Reported [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		657		1,316
Net cash provided by operating activities				2,684
As Previously Reported [Member] | HCA Healthcare, Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		657		1,316
Net cash provided by operating activities				357
As Previously Reported [Member] | HCA Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		(476)		(939)
Net cash provided by operating activities				(1,112)
As Previously Reported [Member] | Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		862		1,680
Net cash provided by operating activities				2,191
As Previously Reported [Member] | Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		272		525
Net cash provided by operating activities				1,248
As Previously Reported [Member] | Eliminations [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		(658)		(1,266)
Adjustment [Member] | Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		104		185
Net cash provided by operating activities				278
Adjustment [Member] | Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income attributable to HCA Healthcare, Inc.		$ (104)		(185)
Net cash provided by operating activities				$ (278)