Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 3,023.9	$ 2,548.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,409.9	1,865.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	614.0	683.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
Net Amount	614.0	683.0
Total Derivatives Not Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	292.5	1,105.2
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0
NET AMOUNT	292.5	1,105.2
Offsetting Derivative Liabilities [Abstract]
GROSS RECOGNIZED LIABILITIES	3,316.4	3,654.1
Derivative Liabilities	906.5	1,788.2
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	906.5	1,788.2
Securities Sold under Agreements to Repurchase(2)
GROSS RECOGNIZED LIABILITIES	50,304.8	11,991.1
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	49,758.9	11,423.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	545.9	567.2
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	545.9	567.2
Other liabilities	3,700.0	3,200.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	2,527.7	2,082.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,380.6	1,826.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	147.1	255.6
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
Net Amount	147.1	255.6
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	467.3	426.5
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2.1	5.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	465.2	420.6
Net Amount	465.2	420.6
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES		5.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET		0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		5.3
Net Amount		5.3
Other Financial Derivatives | Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	28.9	34.8
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	27.2	33.3
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	1.7	1.5
Net Amount	$ 1.7	$ 1.5