Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 2,277.2	$ 3,738.0
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,088.3	2,817.1
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	188.9	920.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.9	0.5
Net Amount	188.0	920.4
Total Derivatives Not Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	273.7	1,144.8
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0
NET AMOUNT	273.7	1,144.8
Offsetting Derivative Liabilities [Abstract]
GROSS RECOGNIZED LIABILITIES	2,550.9	4,882.8
Derivative Liabilities	462.6	2,065.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.9	0.5
NET AMOUNT	461.7	2,065.2
Securities Sold under Agreements to Repurchase
GROSS RECOGNIZED LIABILITIES	529.1	39.8
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	529.1	39.8
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	529.1	39.8
Other liabilities	3,600.0	3,500.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	2,132.6	3,577.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,021.1	2,718.6
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	111.5	859.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.9	0.5
Net Amount	110.6	858.6
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	106.2	125.0
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	67.2	98.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	39.0	26.5
Net Amount	39.0	26.5
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES		0.0
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET		0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		0.0
Net Amount		0.0
Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	38.4	35.3
Net Amount	38.4	35.3
Other Financial Derivatives | Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	38.4	35.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	$ 0.0	$ 0.0