Short-Term Borrowings and Long-Term Debt - Short-term Borrowings (Details) $ in Billions	Dec. 31, 2021 USD ($)
Short-term FHLB advances
Short-term Debt [Line Items]
FHLB advances	$ 7.3
Amount of unused FHLB credit facility	6.3
FRB advances
Short-term Debt [Line Items]
Carrying value of collateral pledged	0.8
Line of credit, remaining borrowing capacity	0.8
Uncommitted federal funds lines
Short-term Debt [Line Items]
Line of credit, remaining borrowing capacity	2.2
Master repurchase agreements
Short-term Debt [Line Items]
Line of credit, remaining borrowing capacity	$ 5.5