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		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenues From Third Party Payers [Line Items]
Revenues	$ 18,605	$ 17,492	$ 36,926	$ 34,831
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	$ 2,803	$ 2,621	$ 5,698	$ 5,459
Revenues from third party payers, Ratio	15.10%	15.00%	15.40%	15.70%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 3,352	$ 2,913	$ 6,651	$ 5,939
Revenues from third party payers, Ratio	18.00%	16.70%	18.00%	17.00%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,440	$ 1,166	$ 2,630	$ 2,189
Revenues from third party payers, Ratio	7.70%	6.70%	7.10%	6.30%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 899	$ 1,033	$ 1,778	$ 2,011
Revenues from third party payers, Ratio	4.80%	5.90%	4.80%	5.80%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 9,124	$ 8,549	$ 18,165	$ 17,094
Revenues from third party payers, Ratio	49.10%	48.70%	49.20%	49.00%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 461	$ 416	$ 906	$ 828
Revenues from third party payers, Ratio	2.50%	2.40%	2.50%	2.40%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 526	$ 794	$ 1,098	$ 1,311
Other, Ratio	2.80%	4.60%	3.00%	3.80%