Offsetting of Assets and Liabilities - Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	$ 4,162.8	$ 3,307.8
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,910.4	3,126.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	2,252.4	181.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	23.6	12.2
Derivative Assets	2,228.8	168.9
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	1,195.7	260.4
Total Derivatives
GROSS RECOGNIZED ASSETS	5,358.5	3,568.2
Derivative Asset	3,448.1	441.5
NET AMOUNT	3,424.5	429.3
Securities Purchased under Agreements to Resell
GROSS RECOGNIZED ASSETS	65,338.8	62,860.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	64,912.8	62,075.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	426.0	784.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	426.0	784.7
NET AMOUNT	0.0	0.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	3,801.6	3,006.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,745.2	2,937.2
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	2,056.4	69.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	23.6	12.2
Derivative Assets	2,032.8	56.9
Interest Rate Swaps | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	359.3	301.4
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	165.2	189.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	194.1	111.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
Derivative Assets	194.1	111.9
Interest Rate Swaps | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	1.9	0.1
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	1.9	0.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
Derivative Assets	$ 1.9	$ 0.1