Income Taxes - Schedule of Reconciliation of Federal Statutory Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	2.90%	2.20%	2.10%
Change in liability for uncertain tax positions	(0.10%)		(1.00%)
Tax benefit from settlements of employee equity awards	(2.40%)	(2.00%)	(3.60%)
Impact of Tax Act on deferred tax balances	(1.60%)	7.80%
Other items, net	0.20%	(0.50%)	(0.20%)
Effective income tax rate on income attributable to HCA Healthcare, Inc.	20.00%	42.50%	32.30%
Income attributable to noncontrolling interests from consolidated partnerships	(2.30%)	(5.10%)	(3.60%)
Effective income tax rate on income before income taxes	17.70%	37.40%	28.70%