Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Schedule of Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 578			$ 732
Accounts receivable	6,532			6,501
Inventories	1,634			1,573
Other	1,266			1,171
Total current assets	10,010			9,977
Property and equipment, net	19,041			17,895
Investments of insurance subsidiaries	367			418
Investments in and advances to affiliates	238			199
Goodwill and other intangible assets	7,759			7,394
Other	629			710
Total assets	38,044			36,593
Current liabilities:
Accounts payable	2,414			2,606
Accrued salaries	1,456			1,369
Other accrued expenses	2,170			1,983
Long-term debt due within one year	191			200
Total current liabilities	6,231			6,158
Long-term debt, net	32,916			32,858
Professional liability risks	1,239			1,198
Income taxes and other liabilities	1,388			1,374
Total liabilities	41,774			41,588
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(5,605)			(6,806)
Noncontrolling interests	1,875			1,811
Total stockholders' deficit	(3,730)	$ (4,125)	$ (4,434)	(4,995)	$ (5,066)	$ (5,079)	$ (5,357)	$ (5,633)
Total liabilities and stockholders' deficit	38,044			36,593
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(5,605)			(6,806)
Noncontrolling interests	1,875			1,811
Total stockholders' deficit	(3,730)	$ (4,125)	$ (4,434)	(4,995)	$ (5,066)	$ (5,079)	$ (5,357)	$ (5,633)
Total liabilities and stockholders' deficit	38,044			36,593
HCA Healthcare, Inc. Issuer [Member]
Current assets:
Cash and cash equivalents				1
Other	47
Total current assets	47			1
Investments in and advances to affiliates	32,263			29,581
Other	389			510
Total assets	32,699			30,092
Current liabilities:
Other accrued expenses	10			29
Total current liabilities	10			29
Long-term debt, net	996			995
Intercompany balances	36,790			35,322
Income taxes and other liabilities	508			552
Total liabilities	38,304			36,898
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(5,605)			(6,806)
Total stockholders' deficit	(5,605)			(6,806)
Total liabilities and stockholders' deficit	32,699			30,092
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(5,605)			(6,806)
Total stockholders' deficit	(5,605)			(6,806)
Total liabilities and stockholders' deficit	32,699			30,092
HCA Inc. Issuer [Member]
Current assets:
Other	106			50
Total assets	106			50
Current liabilities:
Other accrued expenses	296			378
Long-term debt due within one year	97			97
Total current liabilities	393			475
Long-term debt, net	31,471			31,367
Intercompany balances	(7,734)			(9,742)
Total liabilities	24,130			22,100
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(24,024)			(22,050)
Total stockholders' deficit	(24,024)			(22,050)
Total liabilities and stockholders' deficit	106			50
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(24,024)			(22,050)
Total stockholders' deficit	(24,024)			(22,050)
Total liabilities and stockholders' deficit	106			50
Subsidiary Guarantors [Member]
Current assets:
Cash and cash equivalents	105			112
Accounts receivable	3,854			3,693
Inventories	1,088			1,030
Other	667			663
Total current assets	5,714			5,498
Property and equipment, net	12,192			11,110
Investments in and advances to affiliates	29			22
Goodwill and other intangible assets	5,736			4,893
Other	29			47
Total assets	23,700			21,570
Current liabilities:
Accounts payable	1,627			1,793
Accrued salaries	914			862
Other accrued expenses	790			536
Long-term debt due within one year	61			64
Total current liabilities	3,392			3,255
Long-term debt, net	281			307
Intercompany balances	(27,263)			(25,228)
Income taxes and other liabilities	364			357
Total liabilities	(23,226)			(21,309)
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	46,846			42,755
Noncontrolling interests	80			124
Total stockholders' deficit	46,926			42,879
Total liabilities and stockholders' deficit	23,700			21,570
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	46,846			42,755
Noncontrolling interests	80			124
Total stockholders' deficit	46,926			42,879
Total liabilities and stockholders' deficit	23,700			21,570
Subsidiary Non-Guarantors [Member]
Current assets:
Cash and cash equivalents	473			619
Accounts receivable	2,678			2,808
Inventories	546			543
Other	552			508
Total current assets	4,249			4,478
Property and equipment, net	6,849			6,785
Investments of insurance subsidiaries	367			418
Investments in and advances to affiliates	209			177
Goodwill and other intangible assets	2,023			2,501
Other	105			103
Total assets	13,802			14,462
Current liabilities:
Accounts payable	787			813
Accrued salaries	542			507
Other accrued expenses	1,074			1,040
Long-term debt due within one year	33			39
Total current liabilities	2,436			2,399
Long-term debt, net	168			189
Intercompany balances	(1,793)			(352)
Professional liability risks	1,239			1,198
Income taxes and other liabilities	516			465
Total liabilities	2,566			3,899
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	9,441			8,876
Noncontrolling interests	1,795			1,687
Total stockholders' deficit	11,236			10,563
Total liabilities and stockholders' deficit	13,802			14,462
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	9,441			8,876
Noncontrolling interests	1,795			1,687
Total stockholders' deficit	11,236			10,563
Total liabilities and stockholders' deficit	13,802			14,462
Eliminations [Member]
Current assets:
Investments in and advances to affiliates	(32,263)			(29,581)
Total assets	(32,263)			(29,581)
Current liabilities:
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(32,263)			(29,581)
Total stockholders' deficit	(32,263)			(29,581)
Total liabilities and stockholders' deficit	(32,263)			(29,581)
Stockholders' (deficit) equity attributable to HCA Healthcare, Inc.	(32,263)			(29,581)
Total stockholders' deficit	(32,263)			(29,581)
Total liabilities and stockholders' deficit	$ (32,263)			$ (29,581)