Offsetting of Assets and Liabilities (Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	$ 4,975.0	$ 1,902.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,482.8	1,533.8
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	2,492.2	368.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	12.1	2.8
NET AMOUNT	2,480.1	366.1
Total Derivatives Not Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	1,385.1	444.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	1,385.1	444.7
Total Derivatives
GROSS RECOGNIZED ASSETS	6,360.1	2,347.4
Derivative Assets	3,877.3	813.6
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	12.1	2.8
NET AMOUNT	3,865.2	810.8
Securities Purchased under Agreements to Resell
GROSS RECOGNIZED ASSETS	8,133.3	2,078.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	6,967.1	1,392.5
Securities Purchased under Agreements to Resell	1,166.2	686.4
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	1,166.2	686.4
Other assets excluding derivatives and non financial instruments	8,800.0	7,800.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	4,765.6	1,762.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,351.5	1,530.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	2,414.1	232.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	12.1	2.8
NET AMOUNT	2,402.0	229.2
Interest Rate Swap Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	194.0	140.0
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	129.4	3.1
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	64.6	136.9
NET AMOUNT	64.6	$ 136.9
Interest Rate Swap Contracts | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	13.5
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	13.5
NET AMOUNT	13.5
Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	1.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	0.0
NET AMOUNT	$ 0.0