Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Depreciation and fixed asset basis differences, Assets	$ 0	$ 0
Allowances for professional liability and other risks, Assets	452	430
Accounts receivable, Assets	363	368
Compensation, Assets	308	402
Right-of-use lease obligations	506	451
Other, Assets	592	536
Deferred tax assets	2,221	2,187
Depreciation and fixed asset basis differences, Liabilities	1,048	938
Allowances for professional liability and other risks, Liabilities	0	0
Accounts receivable, Liabilities	0	0
Compensation, Liabilities	0	0
Right-of-use lease assets and obligations	492	438
Other, Liabilities	860	698
Deferred tax liabilities	$ 2,400	$ 2,074