Securities Purchased Under Agreements to Resell and Securities Sold Under Agreements to Repurchase - Securities Purchased under Agreements to Resell (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Balance at December 31	$ 784.7	$ 1,070.3
Average Balance During the Year	$ 950.9	$ 1,071.2
Average Interest Rate Earned During the Year	166.71%	9.68%
Maximum Month-End Balance During the Year	$ 1,326.2	$ 1,320.8
Securities purchased under agreements to resell, netting impact	$ 29,100.0	$ 3,600.0