Fair Value of Assets and Liabilities - Summary Of Differences Between The Fair Value Carrying Amount Of Mortgages Held-For-Sale And Aggregate Unpaid Principal Amount (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	$ 88	$ 51
Held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	88	51
Fair value carrying amount less aggregate unpaid principal - Total loans	(8)	(7)
Nonaccrual loans	2	5
Fair value carrying amount less aggregate unpaid principal - Nonaccrual loans	(3)	(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
Aggregate unpaid principal | Held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	96	58
Nonaccrual loans	$ 5	8
Loans 90 days or more past due and still accruing		$ 1