Borrowed Funds (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Borrowed funds	$ 66,167	$ 58,713
Parent Company
Debt Instrument [Line Items]
Borrowed funds	19,578	13,103
Parent Company | Senior debt
Debt Instrument [Line Items]
Borrowed funds	17,880	11,374
Basis adjustments - Fair value accounting hedges	(1,214)
Parent Company | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	1,493	1,524
Basis adjustments - Fair value accounting hedges	(104)
Subsidiaries
Debt Instrument [Line Items]
Borrowed funds	43,557	41,936
Subsidiaries | Senior debt
Debt Instrument [Line Items]
Borrowed funds	4,527	5,283
Basis adjustments - Fair value accounting hedges	(254)
Subsidiaries | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	3,030	$ 4,578
Basis adjustments - Fair value accounting hedges	$ (262)