Commitments and Contingent Liabilities - Summary of Off-Balance Sheet Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 265,837.5	$ 162,025.4
OVER ONE YEAR	19,549.9	17,732.6
TOTAL	285,387.4	179,758.0
Legally Binding Commitments to Extend Credit
Loss Contingencies [Line Items]
Commitments, participated to others	222.2	266.6
Financial Guarantee
Loss Contingencies [Line Items]
ONE YEAR AND LESS	140,539.1	130,311.0
OVER ONE YEAR	0.0	0.0
TOTAL	140,539.1	130,311.0
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	39.1	35.1
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	84,600.0
Guarantees to sponsored member programs		16,300.0
Legally Binding Commitments to Extend Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,849.5	13,639.2
OVER ONE YEAR	18,909.6	17,321.4
TOTAL	30,759.1	30,960.6
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	85,752.0	17,553.0
OVER ONE YEAR	639.0	409.9
TOTAL	86,391.0	17,962.9
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	29.2	25.4
OVER ONE YEAR	1.3	1.3
TOTAL	30.5	26.7
Unsettled Reverse Repurchase Agreements
Loss Contingencies [Line Items]
ONE YEAR AND LESS	27,667.7	496.8
OVER ONE YEAR	0.0	0.0
TOTAL	$ 27,667.7	$ 496.8