Derivative Financial Instruments - Location and Amount of Fair Value Hedge Derivative Gains and Losses Recorded in Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 7,325.0	$ 2,877.7	$ 1,406.5
Interest Expense	5,343.0	990.5	23.8
Other Operating Income	228.7	191.3	243.9
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	47.1	(4.4)	(16.2)
Total gain/(loss) recognized on cash flow hedges	34.9	0.6	10.5
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(86.5)	24.1	57.1
Total gain/(loss) recognized on cash flow hedges	0.0	0.0	0.0
OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	0.0	0.0	0.0
Total gain/(loss) recognized on cash flow hedges	1.9	(4.3)	(6.0)
Interest Rate Contracts | INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Contracts, Recognized on Derivatives	(132.6)	82.8	39.1
Interest Rate Contracts, Recognized on Hedged Items	132.6	(82.8)	(39.1)
Interest Rate Contracts, Amounts Related to Interest Settlements on Derivatives	47.1	(4.4)	(16.2)
Interest Rate Contracts | INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Contracts, Recognized on Derivatives	74.9	(373.4)	(161.6)
Interest Rate Contracts, Recognized on Hedged Items	(74.9)	373.4	161.6
Interest Rate Contracts, Amounts Related to Interest Settlements on Derivatives	(86.5)	24.1	57.1
Interest Rate Contracts | OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Contracts, Recognized on Derivatives	0.0	0.0	0.0
Interest Rate Contracts, Recognized on Hedged Items	0.0	0.0	0.0
Interest Rate Contracts, Amounts Related to Interest Settlements on Derivatives	0.0	0.0	0.0
Foreign Exchange Contracts | INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gain/(loss) recognized on cash flow hedges	34.9	0.6	10.5
Foreign Exchange Contracts | INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gain/(loss) recognized on cash flow hedges	0.0	0.0	0.0
Foreign Exchange Contracts | OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gain/(loss) recognized on cash flow hedges	$ 1.9	$ (4.3)	$ (6.0)