Commitments and Contingent Liabilities (Summary of Off-Balance Sheet Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 255,670.7	$ 265,837.5
OVER ONE YEAR	19,284.4	19,549.9
TOTAL	274,955.1	285,387.4
Undrawn Commitments
Loss Contingencies [Line Items]
Commitments, participated to others	259.1	222.2
Securities Lent with Indemnification
Loss Contingencies [Line Items]
ONE YEAR AND LESS	138,278.1	140,539.1
OVER ONE YEAR	0.0	0.0
TOTAL	138,278.1	140,539.1
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	41.0	39.1
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	89,300.0	84,600.0
Undrawn Commitments
Loss Contingencies [Line Items]
ONE YEAR AND LESS	10,322.2	11,849.5
OVER ONE YEAR	18,957.1	18,909.6
TOTAL	29,279.3	30,759.1
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	90,610.8	85,752.0
OVER ONE YEAR	327.2	639.0
TOTAL	90,938.0	86,391.0
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	17.2	29.2
OVER ONE YEAR	0.1	1.3
TOTAL	17.3	30.5
Reverse repurchase agreements
Loss Contingencies [Line Items]
ONE YEAR AND LESS	16,442.4	27,667.7
OVER ONE YEAR	0.0	0.0
TOTAL	$ 16,442.4	$ 27,667.7