Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Summary of Restatement Adjustments to Financial Statements (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc	$ 474	$ 426	$ 657	$ 659	$ 920	$ 618	$ 658	$ 694	$ 2,216	$ 2,890	$ 2,129
Total assets	36,593				33,758				36,593	33,758	32,744
Total liabilities	41,588				39,391				41,588	39,391
Net cash provided (used in) operating activities									5,426	5,653	4,734
HCA Healthcare, Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc									2,216	2,890	2,129
Total assets	30,092				27,922				30,092	27,922
Total liabilities	36,898				35,224				36,898	35,224
Net cash provided (used in) operating activities									251	322	(184)
HCA Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc									(1,973)	(1,586)	(1,625)
Total assets	50								50
Total liabilities	22,100				20,097				22,100	20,097
Net cash provided (used in) operating activities									(2,096)	(1,756)	(1,404)
Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc									3,920	3,648	3,350
Total assets	21,570				20,237				21,570	20,237
Total liabilities	(21,309)				(18,776)				(21,309)	(18,776)
Net cash provided (used in) operating activities									5,314	4,998	4,304
Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc									529	676	627
Total assets	14,462				12,644				14,462	12,644
Total liabilities	3,899				2,846				3,899	2,846
Net cash provided (used in) operating activities									1,957	2,089	2,018
Eliminations [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc									(2,476)	(2,738)	(2,352)
Total assets	$ (29,581)				(27,045)				$ (29,581)	(27,045)
As Previously Reported [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										2,890	2,129
Total assets					33,758					33,758
Total liabilities					39,391					39,391
Net cash provided (used in) operating activities										5,653	4,734
As Previously Reported [Member] | HCA Healthcare, Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										2,890	2,129
Total assets					27,922					27,922
Total liabilities					35,224					35,224
Net cash provided (used in) operating activities										322	(184)
As Previously Reported [Member] | HCA Inc. Issuer [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										(1,586)	(1,625)
Total liabilities					20,097					20,097
Net cash provided (used in) operating activities										(1,756)	(1,404)
As Previously Reported [Member] | Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										3,235	2,970
Total assets					14,714					14,714
Total liabilities					(23,194)					(23,194)
Net cash provided (used in) operating activities										4,425	3,772
As Previously Reported [Member] | Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										1,089	1,007
Total assets					18,167					18,167
Total liabilities					7,264					7,264
Net cash provided (used in) operating activities										2,662	2,550
As Previously Reported [Member] | Eliminations [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										(2,738)	(2,352)
Total assets					(27,045)					(27,045)
Adjustment [Member] | Subsidiary Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										413	380
Total assets					5,523					5,523
Total liabilities					4,418					4,418
Net cash provided (used in) operating activities										573	532
Adjustment [Member] | Subsidiary Non-Guarantors [Member]
Adjustments or Reclassifications [Line Items]
Net income (loss) attributable to HCA Healthcare, Inc										(413)	(380)
Total assets					(5,523)					(5,523)
Total liabilities					$ (4,418)					(4,418)
Net cash provided (used in) operating activities										$ (573)	$ (532)