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, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Securities Purchased under Agreements to Resell	$ 426.0	$ 784.7
Average Balance During the Year	$ 727.5	$ 950.9
Average Interest Rate Earned During the Year	459.13%	166.71%
Maximum Month-End Balance During the Year	$ 1,034.6	$ 1,326.2
Securities purchased under agreements to resell, netting impact	$ 62,400.0	$ 29,100.0
Securities purchased under agreements to resell, average rate paid excluding netting impact	5.29%	5.27%