Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 2,758.3	$ 2,806.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,819.9	2,205.4
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	938.4	600.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	938.4	600.9
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	857.5	843.5
Offsetting Derivative Liabilities [Abstract]
GROSS RECOGNIZED LIABILITIES	3,615.8	3,649.8
Derivative Liabilities	1,795.9	1,444.4
NET AMOUNT	1,795.9	1,444.4
Securities Sold under Agreements to Repurchase
GROSS RECOGNIZED LIABILITIES	65,547.4	62,860.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	65,376.6	62,075.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	170.8	784.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	170.8	784.7
NET AMOUNT	0.0	0.0
Other liabilities	3,300.0	4,000.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	2,226.4	2,411.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,784.0	2,175.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	442.4	236.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	442.4	236.0
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	504.1	368.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	9.1	6.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	495.0	362.3
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	495.0	362.3
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES		0.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET		0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		0.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET		0.0
NET AMOUNT		0.9
Other Financial Derivatives | Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	27.8	25.4
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	26.8	23.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	1.0	1.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	$ 1.0	$ 1.7