Basis of Presentation and Significant Accounting Policies - Schedule of Estimated Cost of Uncompensated Care (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounting Policies [Abstract]
Patient care costs (salaries and benefits, supplies, other operating expenses and depreciation and amortization)	$ 11,342	$ 10,606
Cost-to-charges ratio (patient care costs as percentage of gross patient charges)	11.90%	11.80%
Total uncompensated care	$ 7,873	$ 7,085
Multiply by the cost-to-charges ratio	11.90%	11.80%
Estimated cost of total uncompensated care	$ 937	$ 836