Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase - Repurchase Agreements Accounted for as Secured Borrowings (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Sold Under Agreements to Repurchase	$ 784.7	$ 567.2
Maturity Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total borrowings, repurchase agreements	784.7	567.2
Maturity Overnight and Continuous | U.S. Treasury and Agency Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total borrowings, repurchase agreements	$ 784.7	$ 567.2