Basis of Presentation and Significant Accounting Policies - Schedule of Revenues from Third Party Payers, Uninsured and Other Payers (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenues From Third Party Payers [Line Items]
Revenues	$ 14,971	$ 15,276	$ 44,736	$ 43,688
Revenues ratio from third party payers	100.00%	100.00%	100.00%	100.00%
Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,569	$ 2,645	$ 7,790	$ 7,816
Revenues from third party payers, Ratio	17.20%	17.30%	17.40%	17.90%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,229	$ 2,124	$ 6,813	$ 6,281
Revenues from third party payers, Ratio	14.90%	13.90%	15.20%	14.40%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 797	$ 692	$ 1,987	$ 1,722
Revenues from third party payers, Ratio	5.30%	4.50%	4.40%	3.90%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 939	$ 813	$ 3,003	$ 2,369
Revenues from third party payers, Ratio	6.30%	5.30%	6.70%	5.40%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 7,184	$ 7,998	$ 21,480	$ 22,300
Revenues from third party payers, Ratio	47.90%	52.40%	48.10%	51.00%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 311	$ 324	$ 992	$ 995
Revenues from third party payers, Ratio	2.10%	2.10%	2.20%	2.30%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 942	$ 680	$ 2,671	$ 2,205
Other, Ratio	6.30%	4.50%	6.00%	5.10%