Commitments and Contingent Liabilities - Summary of Off-Balance Sheet Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 267,669.9	$ 265,837.5
OVER ONE YEAR	17,783.5	19,549.9
TOTAL	285,453.4	285,387.4
Legally Binding Commitments to Extend Credit
Loss Contingencies [Line Items]
Commitments, participated to others	268.5	222.2
Financial Guarantee
Loss Contingencies [Line Items]
ONE YEAR AND LESS	144,543.7	140,539.1
OVER ONE YEAR	0.0	0.0
TOTAL	144,543.7	140,539.1
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	109.4	39.1
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	110,800.0
Guarantees to sponsored member programs		84,600.0
Legally Binding Commitments to Extend Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	10,849.6	11,849.5
OVER ONE YEAR	17,293.2	18,909.6
TOTAL	28,142.8	30,759.1
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	112,256.3	85,752.0
OVER ONE YEAR	490.1	639.0
TOTAL	112,746.4	86,391.0
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	20.3	29.2
OVER ONE YEAR	0.2	1.3
TOTAL	20.5	30.5
Unsettled Reverse Repurchase Agreements
Loss Contingencies [Line Items]
ONE YEAR AND LESS	0.0	27,667.7
OVER ONE YEAR	0.0	0.0
TOTAL	$ 0.0	$ 27,667.7