Securities Sold Under Agreements to Repurchase (Repurchase Agreements Accounted for as Secured Borrowings) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Sold Under Agreements to Repurchase	$ 511.4	$ 784.7
OVERNIGHT AND CONTINUOUS
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Borrowings	511.4	784.7
OVERNIGHT AND CONTINUOUS | U.S. Treasury and Agency Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Borrowings	$ 511.4	$ 784.7