Commitments and Contingent Liabilities (Summary of Off-Balance Sheet Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 286,638.3	$ 267,669.9
OVER ONE YEAR	17,500.1	17,783.5
TOTAL	304,138.4	285,453.4
Undrawn Commitments
Loss Contingencies [Line Items]
Commitments, participated to others	225.8	268.5
Securities Lent with Indemnification
Loss Contingencies [Line Items]
ONE YEAR AND LESS	155,667.3	144,543.7
OVER ONE YEAR	0.0	0.0
TOTAL	155,667.3	144,543.7
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	148.1	109.4
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	118,200.0	110,800.0
Undrawn Commitments
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,263.0	10,849.6
OVER ONE YEAR	17,011.6	17,293.2
TOTAL	28,274.6	28,142.8
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	119,682.3	112,256.3
OVER ONE YEAR	488.3	490.1
TOTAL	120,170.6	112,746.4
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	25.7	20.3
OVER ONE YEAR	0.2	0.2
TOTAL	$ 25.9	$ 20.5