Borrowed Funds - Breakdown of borrowed funds (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument
Long-term debt	$ 21,267,000,000	$ 21,332,000,000
Total wholesale borrowings
Debt Instrument
Long-term debt	20,250,000,000	20,325,000,000
FHLB advances
Debt Instrument
Long-term debt	19,250,000,000	20,325,000,000
FRB term funding
Debt Instrument
Long-term debt	1,000,000,000	0	$ 0
Junior subordinated debentures
Debt Instrument
Long-term debt	579,000,000	575,000,000
Subordinated notes
Debt Instrument
Long-term debt	$ 438,000,000	$ 432,000,000