Borrowed Funds (FHLB Borrowings, Bank Notes, Senior Debt and Subordinated Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Borrowed funds	$ 72,737	$ 58,713
Total FHLB, Senior and Sub Debt	69,711	55,039
Parent Company
Debt Instrument [Line Items]
Borrowed funds	23,971	13,103
Bank
Debt Instrument [Line Items]
Borrowed funds	45,740	41,936
Senior Notes | Parent Company
Debt Instrument [Line Items]
Borrowed funds	$ 22,221	11,374
Senior Notes | Parent Company | Minimum
Debt Instrument [Line Items]
Stated interest rate	1.15%
Senior Notes | Parent Company | Maximum
Debt Instrument [Line Items]
Stated interest rate	6.88%
Senior Notes | Bank
Debt Instrument [Line Items]
Borrowed funds	$ 4,615	5,283
Senior Notes | Bank | Minimum
Debt Instrument [Line Items]
Stated interest rate	2.50%
Senior Notes | Bank | Maximum
Debt Instrument [Line Items]
Stated interest rate	6.14%
Subordinated Debt | Parent Company
Debt Instrument [Line Items]
Borrowed funds	$ 1,544	1,524
Subordinated Debt | Parent Company | Minimum
Debt Instrument [Line Items]
Stated interest rate	3.90%
Subordinated Debt | Parent Company | Maximum
Debt Instrument [Line Items]
Stated interest rate	4.63%
Subordinated Debt | Bank
Debt Instrument [Line Items]
Borrowed funds	$ 3,125	4,578
Subordinated Debt | Bank | Minimum
Debt Instrument [Line Items]
Stated interest rate	2.70%
Subordinated Debt | Bank | Maximum
Debt Instrument [Line Items]
Stated interest rate	5.90%
Junior Subordinated Debt | Parent Company
Debt Instrument [Line Items]
Stated interest rate	6.21%
Borrowed funds	$ 206	205
FHLB | Bank
Debt Instrument [Line Items]
Borrowed funds	$ 38,000	$ 32,075
FHLB | Bank | Minimum
Debt Instrument [Line Items]
Stated interest rate	5.59%
FHLB | Bank | Maximum
Debt Instrument [Line Items]
Stated interest rate	5.99%