Offsetting of Assets and Liabilities - Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 2,806.3	$ 2,548.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,205.4	1,865.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	600.9	683.0
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	600.9	683.0
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	843.5	1,105.2
Total Derivatives
GROSS RECOGNIZED LIABILITIES	3,649.8	3,654.1
Derivative Liabilities	1,444.4	1,788.2
NET AMOUNT	1,444.4	1,788.2
Securities Sold under Agreements to Repurchase
GROSS RECOGNIZED LIABILITIES	62,860.2	11,991.1
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	62,075.5	11,423.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	784.7	567.2
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	784.7	567.2
NET AMOUNT	0.0	0.0
Other liabilities	4,000.0	3,200.0
Foreign Exchange Contracts | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	2,411.7	2,082.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,175.7	1,826.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	236.0	255.6
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	236.0	255.6
Interest Rate Swaps | Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	368.3	426.5
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	6.0	5.9
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	362.3	420.6
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	362.3	420.6
Interest Rate Swaps | Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	0.9	5.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	0.9	5.3
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	0.9	5.3
Other Financial Derivatives | Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	25.4	34.8
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	23.7	33.3
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	1.7	1.5
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0.0	0.0
NET AMOUNT	$ 1.7	$ 1.5