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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues From Third Party Payers [Line Items]
Revenues	$ 17,487	$ 16,213	$ 52,318	$ 47,665
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	$ 2,584	$ 2,560	$ 8,043	$ 7,865
Revenues from third party payers, Ratio	14.80%	15.80%	15.40%	16.50%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,949	$ 2,535	$ 8,888	$ 7,635
Revenues from third party payers, Ratio	16.90%	15.60%	17.00%	16.00%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,208	$ 1,001	$ 3,316	$ 2,478
Revenues from third party payers, Ratio	6.90%	6.20%	6.30%	5.20%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,031	$ 1,039	$ 3,042	$ 2,846
Revenues from third party payers, Ratio	5.90%	6.40%	5.80%	6.00%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 8,497	$ 7,687	$ 25,591	$ 23,140
Revenues from third party payers, Ratio	48.60%	47.40%	49.00%	48.50%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 424	$ 375	$ 1,252	$ 1,127
Revenues from third party payers, Ratio	2.40%	2.30%	2.40%	2.40%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 794	$ 1,016	$ 2,186	$ 2,574
Other, Ratio	4.50%	6.30%	4.10%	5.40%