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	Mar. 31, 2026	Dec. 31, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	$ 167	$ 151
Held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	167	151
Fair value carrying amount less aggregate unpaid principal - Total loans	(3)	(3)
Nonaccrual loans	7	9
Fair value carrying amount less aggregate unpaid principal - Nonaccrual loans	(3)	(3)
Held for sale | Aggregate unpaid principal
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	170	154
Nonaccrual loans	$ 10	$ 12