Borrowed Funds (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Borrowed funds	$ 60,822	$ 58,713
Parent Company
Debt Instrument [Line Items]
Borrowed funds	16,041	13,103
Parent Company | Senior debt
Debt Instrument [Line Items]
Borrowed funds	14,287	11,374
Basis adjustments - Fair value accounting hedges	(557)
Parent Company | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	1,549	1,524
Basis adjustments - Fair value accounting hedges	(47)
Subsidiaries
Debt Instrument [Line Items]
Borrowed funds	41,231	41,936
Subsidiaries | Senior debt
Debt Instrument [Line Items]
Borrowed funds	5,335	5,283
Basis adjustments - Fair value accounting hedges	(202)
Subsidiaries | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	3,876	$ 4,578
Basis adjustments - Fair value accounting hedges	$ (179)