Fair Value of Assets and Liabilities - Schedule of Differences between the Fair Value Carrying Amount of Mortgages Held-for-sale and Aggregate Unpaid Principal Amount (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	$ 114	$ 85
Held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	114	85
Fair value carrying amount less aggregate unpaid principal - Total loans	(4)	(4)
Nonaccrual loans	7	3
Fair value carrying amount less aggregate unpaid principal - Nonaccrual loans	(4)	(2)
Held for sale | Aggregate unpaid principal
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	118	89
Nonaccrual loans	$ 11	$ 5