Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Schedule of Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ 896	$ 530	$ 3,144	$ 2,102
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Changes in operating assets and liabilities			(147)	(289)
Depreciation and amortization	582	539	1,697	1,581
Income taxes				(9)
Gain on sales of facilities	(6)	(7)	(420)	(10)
Losses on retirement of debt	9	39	9	39
Amortization of debt issuance costs			23	23
Share-based compensation			204	195
Other			76	60
Net cash provided by (used in) operating activities			4,586	3,692
Cash flows from investing activities:
Purchase of property and equipment			(2,420)	(2,033)
Acquisition of hospitals and health care entities			(1,056)	(1,142)
Disposition of hospitals and health care entities			802	24
Change in investments			65	(15)
Other			(6)	(6)
Net cash used in investing activities			(2,615)	(3,172)
Cash flows from financing activities:
Issuance of long-term debt			2,000	1,502
Net change in revolving credit facilities			(330)	650
Repayment of long-term debt			(1,652)	(700)
Distributions to noncontrolling interests			(315)	(363)
Payment of debt issuance costs			(24)	(25)
Payment of cash dividends			(366)
Repurchases of common stock			(1,195)	(1,475)
Other			(232)	(37)
Net cash (used in) provided by financing activities			(2,114)	(448)
Effect on exchange rate changes on cash and cash equivalents			(11)
Change in cash and cash equivalents			(154)	72
Cash and cash equivalents at beginning of period			732	646
Cash and cash equivalents at end of period	578	718	578	718
Eliminations [Member]
Cash flows from operating activities:
Net income (loss)	(728)	(436)	(2,670)	(1,702)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity in earnings of affiliates			2,670	1,702
HCA Healthcare, Inc. Issuer [Member]
Cash flows from operating activities:
Net income (loss)	759	426	2,723	1,742
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Changes in operating assets and liabilities			(15)	(15)
Income taxes				(9)
Equity in earnings of affiliates			(2,670)	(1,702)
Other			67	58
Net cash provided by (used in) operating activities			105	74
Cash flows from financing activities:
Payment of cash dividends			(366)
Repurchases of common stock			(1,195)	(1,475)
Changes in intercompany balances with affiliates, net			1,697	1,468
Other			(242)	(66)
Net cash (used in) provided by financing activities			(106)	(73)
Change in cash and cash equivalents			(1)	1
Cash and cash equivalents at beginning of period			1
Cash and cash equivalents at end of period		1		1
HCA Inc. Issuer [Member]
Cash flows from operating activities:
Net income (loss)	(708)	(524)	(2,016)	(1,463)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Changes in operating assets and liabilities			(83)	(293)
Losses on retirement of debt	9	39	9	39
Amortization of debt issuance costs			23	23
Net cash provided by (used in) operating activities			(2,067)	(1,694)
Cash flows from financing activities:
Issuance of long-term debt			2,000	1,500
Net change in revolving credit facilities			(330)	650
Repayment of long-term debt			(1,566)	(604)
Payment of debt issuance costs			(24)	(25)
Changes in intercompany balances with affiliates, net			1,987	173
Net cash (used in) provided by financing activities			2,067	1,694
Subsidiary Guarantors [Member]
Cash flows from operating activities:
Net income (loss)	1,275	928	4,151	2,843
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Changes in operating assets and liabilities			(154)	(191)
Depreciation and amortization	340	311	992	923
Gain on sales of facilities	(6)	(3)	(378)	(6)
Share-based compensation			204	195
Other				2
Net cash provided by (used in) operating activities			4,815	3,766
Cash flows from investing activities:
Purchase of property and equipment			(1,425)	(1,161)
Acquisition of hospitals and health care entities			(894)	(9)
Disposition of hospitals and health care entities			770	12
Change in investments			19	1
Other			(18)	(7)
Net cash used in investing activities			(1,548)	(1,164)
Cash flows from financing activities:
Repayment of long-term debt			(44)	(54)
Distributions to noncontrolling interests			(63)	(105)
Changes in intercompany balances with affiliates, net			(3,167)	(2,439)
Other				1
Net cash (used in) provided by financing activities			(3,274)	(2,597)
Change in cash and cash equivalents			(7)	5
Cash and cash equivalents at beginning of period			112	114
Cash and cash equivalents at end of period	105	119	105	119
Subsidiary Non-Guarantors [Member]
Cash flows from operating activities:
Net income (loss)	298	136	956	682
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Changes in operating assets and liabilities			105	210
Depreciation and amortization	242	228	705	658
Gain on sales of facilities		(4)	(42)	(4)
Other			9
Net cash provided by (used in) operating activities			1,733	1,546
Cash flows from investing activities:
Purchase of property and equipment			(995)	(872)
Acquisition of hospitals and health care entities			(162)	(1,133)
Disposition of hospitals and health care entities			32	12
Change in investments			46	(16)
Other			12	1
Net cash used in investing activities			(1,067)	(2,008)
Cash flows from financing activities:
Issuance of long-term debt				2
Repayment of long-term debt			(42)	(42)
Distributions to noncontrolling interests			(252)	(258)
Changes in intercompany balances with affiliates, net			(517)	798
Other			10	28
Net cash (used in) provided by financing activities			(801)	528
Effect on exchange rate changes on cash and cash equivalents			(11)
Change in cash and cash equivalents			(146)	66
Cash and cash equivalents at beginning of period			619	532
Cash and cash equivalents at end of period	$ 473	$ 598	$ 473	$ 598