Borrowed Funds (FHLB Borrowings, Senior Debt and Subordinated Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Borrowed funds	$ 72,707	$ 72,737
Total FHLB, Senior and Sub Debt	69,734	69,711
Parent Company
Debt Instrument [Line Items]
Borrowed funds	25,039	23,971
Parent Company | Senior debt
Debt Instrument [Line Items]
Borrowed funds	$ 23,303	22,221
Parent Company | Senior debt | Minimum
Debt Instrument [Line Items]
Interest rate	1.15%
Parent Company | Senior debt | Maximum
Debt Instrument [Line Items]
Interest rate	6.88%
Parent Company | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	$ 1,530	1,544
Parent Company | Subordinated debt | Minimum
Debt Instrument [Line Items]
Interest rate	3.90%
Parent Company | Subordinated debt | Maximum
Debt Instrument [Line Items]
Interest rate	4.63%
Parent Company | Junior subordinated debt
Debt Instrument [Line Items]
Interest rate	6.17%
Borrowed funds	$ 206	206
Subsidiaries
Debt Instrument [Line Items]
Borrowed funds	44,695	45,740
Subsidiaries | Senior debt
Debt Instrument [Line Items]
Borrowed funds	$ 4,604	4,615
Subsidiaries | Senior debt | Minimum
Debt Instrument [Line Items]
Interest rate	2.50%
Subsidiaries | Senior debt | Maximum
Debt Instrument [Line Items]
Interest rate	6.07%
Subsidiaries | Subordinated debt
Debt Instrument [Line Items]
Borrowed funds	$ 3,091	3,125
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	$ 37,000	$ 38,000
Subsidiaries | FHLB | Minimum
Debt Instrument [Line Items]
Interest rate	5.52%
Subsidiaries | FHLB | Maximum
Debt Instrument [Line Items]
Interest rate	5.92%