Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Depreciation and fixed asset basis differences, Assets	$ 0	$ 0
Allowances for professional liability and other risks, Assets	395	452
Accounts receivable, Assets	418	363
Compensation, Assets	285	308
Right-of-use lease obligations	478	506
Other, Assets	297	592
Deferred tax assets	1,873	2,221
Depreciation and fixed asset basis differences, Liabilities	1,139	1,048
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	462	492
Other, Liabilities	932	860
Deferred tax liabilities	$ 2,533	$ 2,400