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, 2025	Mar. 31, 2024	Mar. 31, 2023
Revenues From Third Party Payers [Line Items]
Revenues	$ 18,321	$ 17,339
Revenues ratio from third party payers	100.00%	100.00%
Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,895	$ 2,838
Revenues from third party payers, Ratio	15.80%	16.40%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 3,299	$ 3,026
Revenues from third party payers, Ratio	4.80%	17.40%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,190	$ 1,000
Revenues from third party payers, Ratio	6.50%	5.80%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 879	$ 978
Revenues from third party payers, Ratio	18.00%	5.60%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 9,041	$ 8,545
Revenues from third party payers, Ratio		49.20%	49.40%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 445	$ 412
Revenues from third party payers, Ratio	2.40%	2.40%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 572	$ 540
Other, Ratio	3.10%	3.20%