Pledged and Restricted Assets (Type of Pledged Assets) (Details) - USD ($) $ in Billions	Mar. 31, 2022	Dec. 31, 2021
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 51.2	$ 54.6
Obligations of States and Political Subdivisions
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	3.5	3.7
Government Sponsored Agency and Other Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	34.8	35.6
Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 12.9	$ 15.3