Offsetting of Assets and Liabilities (Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell) (Detail) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	$ 1,498.4	$ 3,307.8
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,119.0	3,126.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	379.4	181.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	4.0	12.2
NET AMOUNT	375.4	168.9
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	335.4	260.4
Total Derivatives
GROSS RECOGNIZED ASSETS	1,833.8	3,568.2
Derivative Assets	714.8	441.5
NET AMOUNT	710.8	429.3
Securities Purchased under Agreements to Resell
GROSS RECOGNIZED ASSETS	71,070.3	62,860.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	70,210.7	62,075.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	859.6	784.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	859.6	784.7
NET AMOUNT	0.0	0.0
Other assets excluding derivatives and non financial instruments	11,100.0	10,300.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	1,088.9	3,006.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	943.2	2,937.2
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	145.7	69.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	4.0	12.2
NET AMOUNT	141.7	56.9
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	392.2	301.4
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	175.8	189.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	216.4	111.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	216.4	111.9
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	17.3	0.1
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	17.3	0.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	$ 17.3	$ 0.1