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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues From Third Party Payers [Line Items]
Revenues	$ 15,861	$ 14,820	$ 31,452	$ 29,765
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	$ 2,567	$ 2,495	$ 5,305	$ 5,221
Revenues from third party payers, Ratio	16.20%	16.80%	16.90%	17.50%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,541	$ 2,260	$ 5,100	$ 4,584
Revenues from third party payers, Ratio	16.00%	15.20%	16.20%	15.40%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 742	$ 611	$ 1,477	$ 1,190
Revenues from third party payers, Ratio	4.70%	4.10%	4.70%	4.00%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 894	$ 954	$ 1,807	$ 2,064
Revenues from third party payers, Ratio	5.60%	6.40%	5.70%	6.90%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 7,830	$ 7,144	$ 15,453	$ 14,296
Revenues from third party payers, Ratio	49.40%	48.40%	49.20%	48.10%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 377	$ 325	$ 752	$ 681
Revenues from third party payers, Ratio	2.40%	2.20%	2.40%	2.30%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 910	$ 1,031	$ 1,558	$ 1,729
Other, Ratio	5.70%	6.90%	4.90%	5.80%