Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 2,619.8	$ 2,312.4
Gross Amounts Offset in the Balance Sheet	2,370.7	1,618.4
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	249.1	694.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.1
Net Amount	249.1	693.9
Total Derivatives Not Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	406.0	1,000.6
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0
Net Amount	406.0	1,000.6
Offsetting Derivative Liabilities [Abstract]
GROSS RECOGNIZED LIABILITIES	3,025.8	3,313.0
Derivative Liabilities	655.1	1,694.6
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.1
Net Amount	655.1	1,694.5
Securities Sold under Agreements to Repurchase
GROSS RECOGNIZED LIABILITIES	36.5	489.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	36.5	489.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	36.5	489.7
Other liabilities	4,000.0	3,100.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	2,433.9	2,181.6
Gross Amounts Offset in the Balance Sheet	2,237.7	1,548.6
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	196.2	633.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.1
Net Amount	196.2	632.9
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	154.6	96.7
Gross Amounts Offset in the Balance Sheet	133.0	57.3
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	21.6	39.4
Net Amount	21.6	39.4
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES		0.7
Gross Amounts Offset in the Balance Sheet		0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		0.7
Net Amount		0.7
Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	31.3	20.9
Net Amount	31.3	20.9
Other Financial Derivatives | Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	31.3	33.4
Gross Amounts Offset in the Balance Sheet	$ 0.0	$ 12.5