Commitments and Contingent Liabilities (Summary of Off-Balance Sheet Financial Instruments) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 340,393.9	$ 330,600.4
OVER ONE YEAR	18,061.6	18,825.8
TOTAL	358,455.5	349,426.2
Undrawn Commitments
Loss Contingencies [Line Items]
Commitments, participated to others	142.1	175.1
Securities Lent with Indemnification
Loss Contingencies [Line Items]
ONE YEAR AND LESS	194,000.1	170,738.8
OVER ONE YEAR	0.0	0.0
TOTAL	194,000.1	170,738.8
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	67.7	68.1
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	134,200.0	147,800.0
Undrawn Commitments
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,198.7	10,959.6
OVER ONE YEAR	17,346.5	18,154.7
TOTAL	28,545.2	29,114.3
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	135,166.7	148,883.9
OVER ONE YEAR	715.1	671.0
TOTAL	135,881.8	149,554.9
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	28.4	18.1
OVER ONE YEAR	0.0	0.1
TOTAL	$ 28.4	$ 18.2