Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 1,630.2	$ 2,806.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,070.1	2,205.4
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	560.1	600.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	560.1	600.9
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	186.8	843.5
Offsetting Derivative Liabilities [Abstract]
GROSS RECOGNIZED LIABILITIES	1,817.0	3,649.8
Derivative Liabilities	746.9	1,444.4
NET AMOUNT	746.9	1,444.4
Securities Sold under Agreements to Repurchase
GROSS RECOGNIZED LIABILITIES	66,375.9	62,860.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	65,864.5	62,075.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	511.4	784.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	511.4	784.7
NET AMOUNT	0.0	0.0
Other liabilities	2,900.0	4,000.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	1,131.3	2,411.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,051.2	2,175.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	80.1	236.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	80.1	236.0
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	477.7	368.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2.7	6.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	475.0	362.3
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	475.0	362.3
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	0.2	0.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	0.2	0.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	0.2	0.9
Other Financial Derivatives | Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	21.0	25.4
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	16.2	23.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	4.8	1.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	$ 4.8	$ 1.7