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	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	$ 87	$ 68
Held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	87	68
Fair value carrying amount less aggregate unpaid principal - Total loans	(4)	(5)
Nonaccrual loans	3	2
Fair value carrying amount less aggregate unpaid principal - Nonaccrual loans	(2)	(3)
Loans 90 days or more past due and still accruing		1
Fair value carrying amount less aggregate unpaid principal - Loans 90 days or more past due and still accruing		0
Held for sale | Aggregate unpaid principal
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total loans	91	73
Nonaccrual loans	$ 5	5
Loans 90 days or more past due and still accruing		$ 1