Borrowed Funds (FHLB Borrowings, Senior Debt and Subordinated Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Borrowed funds	$ 66,167	$ 58,713
Total FHLB, Senior and Sub Debt	63,135	55,039
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
Parent Company | Senior debt | Minimum
Debt Instrument [Line Items]
Interest rate	1.20%
Parent Company | Senior debt | Maximum
Debt Instrument [Line Items]
Interest rate	6.00%
Parent Company | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	$ 1,493	1,524
Parent Company | Subordinated debt | Minimum
Debt Instrument [Line Items]
Interest rate	3.90%
Parent Company | Subordinated debt | Maximum
Debt Instrument [Line Items]
Interest rate	4.60%
Parent Company | Junior subordinated debt
Debt Instrument [Line Items]
Interest rate	6.20%
Borrowed funds	$ 205	205
Subsidiaries
Debt Instrument [Line Items]
Borrowed funds	43,557	41,936
Subsidiaries | Senior debt
Debt Instrument [Line Items]
Borrowed funds	$ 4,527	5,283
Subsidiaries | Senior debt | Minimum
Debt Instrument [Line Items]
Interest rate	2.50%
Subsidiaries | Senior debt | Maximum
Debt Instrument [Line Items]
Interest rate	6.10%
Subsidiaries | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	$ 3,030	4,578
Subsidiaries | Subordinated debt | Minimum
Debt Instrument [Line Items]
Interest rate	2.70%
Subsidiaries | Subordinated debt | Maximum
Debt Instrument [Line Items]
Interest rate	5.90%
Subsidiaries | FHLB
Debt Instrument [Line Items]
Borrowed funds	$ 36,000	$ 32,075
Subsidiaries | FHLB | Minimum
Debt Instrument [Line Items]
Interest rate	5.50%
Subsidiaries | FHLB | Maximum
Debt Instrument [Line Items]
Interest rate	5.90%