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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues From Third Party Payers [Line Items]
Revenues	$ 16,213	$ 14,971	$ 47,665	$ 44,736
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	$ 2,560	$ 2,569	$ 7,865	$ 7,790
Revenues from third party payers, Ratio	15.80%	17.20%	16.50%	17.40%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,535	$ 2,229	$ 7,635	$ 6,813
Revenues from third party payers, Ratio	15.60%	14.90%	16.00%	15.20%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,001	$ 797	$ 2,478	$ 1,987
Revenues from third party payers, Ratio	6.20%	5.30%	5.20%	4.40%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,039	$ 939	$ 2,846	$ 3,003
Revenues from third party payers, Ratio	6.40%	6.30%	6.00%	6.70%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 7,687	$ 7,184	$ 23,140	$ 21,480
Revenues from third party payers, Ratio	47.40%	47.90%	48.50%	48.10%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 375	$ 311	$ 1,127	$ 992
Revenues from third party payers, Ratio	2.30%	2.10%	2.40%	2.20%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 1,016	$ 942	$ 2,574	$ 2,671
Other, Ratio	6.30%	6.30%	5.40%	6.00%