Commitments and Contingent Liabilities (Summary of Off-Balance Sheet Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 282,244.7	$ 265,837.5
OVER ONE YEAR	19,476.6	19,549.9
TOTAL	301,721.3	285,387.4
Undrawn Commitments
Loss Contingencies [Line Items]
Commitments, participated to others	203.1	222.2
Securities Lent with Indemnification
Loss Contingencies [Line Items]
ONE YEAR AND LESS	146,058.1	140,539.1
OVER ONE YEAR	0.0	0.0
TOTAL	146,058.1	140,539.1
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	101.8	39.1
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	112,000.0	84,600.0
Undrawn Commitments
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,202.5	11,849.5
OVER ONE YEAR	18,982.6	18,909.6
TOTAL	30,185.1	30,759.1
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	113,405.2	85,752.0
OVER ONE YEAR	493.7	639.0
TOTAL	113,898.9	86,391.0
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	34.8	29.2
OVER ONE YEAR	0.3	1.3
TOTAL	35.1	30.5
Reverse repurchase agreements
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,544.1	27,667.7
OVER ONE YEAR	0.0	0.0
TOTAL	$ 11,544.1	$ 27,667.7