Accounting Policies - Schedule of Estimated Cost of Uncompensated Care (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Patient care costs (salaries and benefits, supplies, other operating expenses and depreciation and amortization)	$ 44,271	$ 44,118	$ 40,035
Cost-to-charges ratio (patient care costs as percentage of gross patient charges)	12.00%	12.00%	12.40%
Total uncompensated care	$ 29,029	$ 31,105	$ 26,757
Multiply by the cost-to-charges ratio	12.00%	12.00%	12.40%
Estimated cost of total uncompensated care	$ 3,483	$ 3,733	$ 3,318