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, 2024	Mar. 31, 2023
Revenues From Third Party Payers [Line Items]
Revenues	$ 17,339	$ 15,591
Revenues ratio from third party payers	100.00%	100.00%
Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,838	$ 2,738
Revenues from third party payers, Ratio	16.40%	17.60%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 3,026	$ 2,559
Revenues from third party payers, Ratio	17.40%	16.40%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,000	$ 735
Revenues from third party payers, Ratio	5.80%	4.70%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 978	$ 913
Revenues from third party payers, Ratio	5.60%	5.90%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues		$ 145
Revenues from third party payers	$ 8,545	$ 7,623
Revenues from third party payers, Ratio	49.20%	48.90%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 412	$ 375
Revenues from third party payers, Ratio	2.40%	2.40%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 540	$ 648
Other, Ratio	3.20%	4.10%