Fair Value Measurements - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Unfunded commitments, equity securities measured at net asset value	$ 21	$ 25
Revaluation period	90 days
Deferred fees	$ 3	3
Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Transfers Out of Level 3	984	269
Transfers into Level 3	93	594
Assets, Transfers Into Level 3	44	42
Assets Transfers out of Level 3	27	64
Level 3 | Equity contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivatives, net, Transfers out of Level 3	7	64
Derivatives, net, Transfers into Level 3	1	8
Unfunded Loan Commitment
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees	162	158
Domestic deposits | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Transfers Out of Level 3	36	30
Transfers into Level 3	0	182
Long-term debt | Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Transfers Out of Level 3	948	239
Transfers into Level 3	93	412
Commercial loans held for sale | Level 3 | Loans
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Transfers Into Level 3	45	37
Assets Transfers out of Level 3	$ 20	$ 0