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
	Mar. 31, 2023	Mar. 31, 2022
Revenues From Third Party Payers [Line Items]
Revenues	$ 15,591	$ 14,945
Revenues ratio from third party payers	100.00%	100.00%
Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,738	$ 2,726
Revenues from third party payers, Ratio	17.60%	18.20%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,559	$ 2,324
Revenues from third party payers, Ratio	16.40%	15.60%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 735	$ 579
Revenues from third party payers, Ratio	4.70%	3.90%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 913	$ 1,110
Revenues from third party payers, Ratio	5.90%	7.40%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 145
Revenues from third party payers	$ 7,623	$ 7,152
Revenues from third party payers, Ratio	48.90%	47.90%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 375	$ 356
Revenues from third party payers, Ratio	2.40%	2.40%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 648	$ 698
Other, Ratio	4.10%	4.60%