Offsetting of Assets and Liabilities - Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Total Derivatives Subject to a Master Netting Arrangement
Assets	$ 1,902.7	$ 4,097.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,533.8	3,507.8
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	368.9	589.4
Gross amounts not offset in the balance sheet	2.8	0.9
Net Amount	366.1	588.5
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	444.7	461.0
Gross amounts not offset in the balance sheet	0.0	0.0
Net Amount	444.7	461.0
Total Derivatives
GROSS RECOGNIZED ASSETS	2,347.4	4,558.2
Derivative Assets	813.6	1,050.4
Gross amounts not offset in the balance sheet	2.8	0.9
Net Amount	810.8	1,049.5
Securities Purchased under Agreements to Resell
GROSS RECOGNIZED ASSETS	2,078.9	1,596.5
Gross amounts offset in the balance sheet	1,392.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	686.4	1,596.5
Gross amounts not offset in the balance sheet	686.4	1,596.5
Other assets (excluding derivative assets)	7,800.0	7,300.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
Assets	1,762.7	3,799.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,530.7	3,505.3
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	232.0	294.4
Gross amounts not offset in the balance sheet	2.8	0.9
Net Amount	229.2	293.5
Interest Rate Swaps | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
Assets	140.0	295.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	3.1	2.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	136.9	293.4
Net Amount	$ 136.9	293.4
Interest Rate Swaps | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
Assets		1.6
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET		0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		1.6
Net Amount		$ 1.6