Derivative Financial Instruments (Location and Amount of Fair Value And Cash Flow Hedge Derivative Gains And Losses Recorded In Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 2,234.0	$ 2,140.9
Interest Expense	1,580.0	1,572.8
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(3.6)	9.0
Gains (Losses) on cash flow hedges reclassified from AOCI to net income	13.4	10.5
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(11.6)	(14.6)
Gains (Losses) on cash flow hedges reclassified from AOCI to net income	0.0	0.0
Interest Rate Contracts | INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	52.8	(99.6)
Recognized on hedged items	(52.8)	99.6
Amounts related to interest settlements on derivatives	(3.6)	9.0
Gains (Losses) on cash flow hedges reclassified from AOCI to net income	(0.4)	0.0
Interest Rate Contracts | INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(9.6)	39.2
Recognized on hedged items	9.6	(39.2)
Amounts related to interest settlements on derivatives	(11.6)	(14.6)
Gains (Losses) on cash flow hedges reclassified from AOCI to net income	0.0	0.0
Foreign Exchange Contracts | INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges reclassified from AOCI to net income	13.8	10.5
Foreign Exchange Contracts | INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges reclassified from AOCI to net income	$ 0.0	$ 0.0