Supplemental Condensed Consolidating Financial Information and Other Collateral-Related Information - Schedule of Condensed Consolidating Comprehensive Income Statement (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
Condensed Statement of Income Captions [Line Items]
Revenues before provision for doubtful accounts									$ 47,653	$ 44,747	$ 43,591
Provision for doubtful accounts									4,039	3,257	3,913
Revenues	$ 11,562	$ 10,696	$ 10,733	$ 10,623	$ 10,641	$ 10,270	$ 10,319	$ 10,260	43,614	41,490	39,678
Salaries and benefits									20,059	18,897	18,115
Supplies									7,316	6,933	6,638
Other operating expenses									8,051	7,496	7,056
Equity in earnings of affiliates									(45)	(54)	(46)
Depreciation and amortization									2,131	1,966	1,904
Interest expense									1,690	1,707	1,665
Losses (gains) on sales of facilities	1	4	1	1	15	2	4	2	(8)	(23)	5
Losses on retirement of debt		25				2			39	4	135
Legal claim costs (benefits)										(246)	249
Total expenses including equity in earnings of affiliates									39,233	36,680	35,721
Income (loss) before income taxes									4,381	4,810	3,957
Provision (benefit) for income taxes									1,638	1,378	1,261
Net income (loss)	641	530	795	777	1,085	745	791	811	2,743	3,432	2,696
Net income attributable to noncontrolling interests									527	542	567
Net income (loss) attributable to HCA Healthcare, Inc.	$ 474	$ 426	$ 657	$ 659	$ 920	$ 618	$ 658	$ 694	2,216	2,890	2,129
Comprehensive income (loss) attributable to HCA Healthcare, Inc.									2,276	2,817	2,187
HCA Healthcare, Inc. Issuer [Member]
Condensed Statement of Income Captions [Line Items]
Other operating expenses									6	6	(2)
Equity in earnings of affiliates									(2,476)	(2,738)	(2,352)
Interest expense									64	64	115
Losses on retirement of debt											122
Legal claim costs (benefits)											120
Total expenses including equity in earnings of affiliates									(2,406)	(2,668)	(1,997)
Income (loss) before income taxes									2,406	2,668	1,997
Provision (benefit) for income taxes									190	(222)	(132)
Net income (loss)									2,216	2,890	2,129
Net income (loss) attributable to HCA Healthcare, Inc.									2,216	2,890	2,129
Comprehensive income (loss) attributable to HCA Healthcare, Inc.									2,276	2,817	2,187
HCA Inc. Issuer [Member]
Condensed Statement of Income Captions [Line Items]
Interest expense									3,088	2,756	2,445
Losses on retirement of debt									39	4	13
Legal claim costs (benefits)										(246)	129
Total expenses including equity in earnings of affiliates									3,127	2,514	2,587
Income (loss) before income taxes									(3,127)	(2,514)	(2,587)
Provision (benefit) for income taxes									(1,154)	(928)	(962)
Net income (loss)									(1,973)	(1,586)	(1,625)
Net income (loss) attributable to HCA Healthcare, Inc.									(1,973)	(1,586)	(1,625)
Comprehensive income (loss) attributable to HCA Healthcare, Inc.									(1,953)	(1,505)	(1,568)
Subsidiary Guarantors [Member]
Condensed Statement of Income Captions [Line Items]
Revenues before provision for doubtful accounts									27,992	26,468	25,711
Provision for doubtful accounts									2,218	2,041	2,329
Revenues									25,774	24,427	23,382
Salaries and benefits									11,619	10,971	10,593
Supplies									4,286	4,090	3,933
Other operating expenses									4,249	3,912	3,685
Equity in earnings of affiliates									(6)	(7)	(8)
Depreciation and amortization									1,237	1,141	1,085
Interest expense									(1,309)	(970)	(816)
Losses (gains) on sales of facilities									(2)	4
Management fees									(621)	(588)	(515)
Total expenses including equity in earnings of affiliates									19,453	18,553	17,957
Income (loss) before income taxes									6,321	5,874	5,425
Provision (benefit) for income taxes									2,293	2,133	1,983
Net income (loss)									4,028	3,741	3,442
Net income attributable to noncontrolling interests									108	93	92
Net income (loss) attributable to HCA Healthcare, Inc.									3,920	3,648	3,350
Comprehensive income (loss) attributable to HCA Healthcare, Inc.									3,898	3,637	3,389
Subsidiary Non-Guarantors [Member]
Condensed Statement of Income Captions [Line Items]
Revenues before provision for doubtful accounts									19,661	18,279	17,880
Provision for doubtful accounts									1,821	1,216	1,584
Revenues									17,840	17,063	16,296
Salaries and benefits									8,440	7,926	7,522
Supplies									3,030	2,843	2,705
Other operating expenses									3,796	3,578	3,373
Equity in earnings of affiliates									(39)	(47)	(38)
Depreciation and amortization									894	825	819
Interest expense									(153)	(143)	(79)
Losses (gains) on sales of facilities									(6)	(27)	5
Management fees									621	588	515
Total expenses including equity in earnings of affiliates									16,583	15,543	14,822
Income (loss) before income taxes									1,257	1,520	1,474
Provision (benefit) for income taxes									309	395	372
Net income (loss)									948	1,125	1,102
Net income attributable to noncontrolling interests									419	449	475
Net income (loss) attributable to HCA Healthcare, Inc.									529	676	627
Comprehensive income (loss) attributable to HCA Healthcare, Inc.									591	533	589
Eliminations [Member]
Condensed Statement of Income Captions [Line Items]
Equity in earnings of affiliates									2,476	2,738	2,352
Total expenses including equity in earnings of affiliates									2,476	2,738	2,352
Income (loss) before income taxes									(2,476)	(2,738)	(2,352)
Net income (loss)									(2,476)	(2,738)	(2,352)
Net income (loss) attributable to HCA Healthcare, Inc.									(2,476)	(2,738)	(2,352)
Comprehensive income (loss) attributable to HCA Healthcare, Inc.									$ (2,536)	$ (2,665)	$ (2,410)