Mortgage Banking Activity - Residential Mortgage Loans (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of period	$ 590
Balance at end of period	613	$ 590
Mortgage loans
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of period	44	250
Originations and purchases	512	1,275
Sales, net of gains	(475)	(1,481)
Balance at end of period	$ 81	$ 44