Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	$ 375.1	$ 360.6
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Amortization and Accretion of Securities and Unearned Income, net	26.1	22.4
Provision for Credit Losses	(30.0)	61.0
Depreciation and Amortization	125.4	123.8
Pension Plan Contributions	(6.7)	(10.6)
Change in Receivables	(66.7)	(122.7)
Change in Interest Payable	7.3	(5.7)
Change in Collateral With Derivative Counterparties, net	(824.2)	(3,570.2)
Other Operating Activities, net	462.0	456.1
Net Cash Provided by (Used in) Operating Activities	68.3	(2,685.3)
CASH FLOWS FROM INVESTING ACTIVITIES
Change in Federal Funds Sold	(0.1)	5.0
Change in Securities Purchased under Agreements to Resell	477.9	(367.2)
Change in Interest-Bearing Deposits with Banks	(772.6)	(757.6)
Net Change in Federal Reserve and Other Central Bank Deposits	8,369.3	(11,204.7)
Purchases of Debt Securities – Held to Maturity	(16,047.6)	(7,076.0)
Proceeds from Maturity and Redemption of Debt Securities – Held to Maturity	16,125.8	6,287.3
Purchases of Debt Securities – Available for Sale	(3,631.9)	(2,857.6)
Proceeds from Sale, Maturity and Redemption of Debt Securities – Available for Sale	2,214.9	2,430.7
Change in Loans and Leases	(592.4)	(6,432.9)
Purchases of Buildings and Equipment	(10.7)	(37.6)
Purchases and Development of Computer Software	(94.8)	(94.8)
Change in Client Security Settlement Receivables	(810.4)	(1,241.9)
Other Investing Activities, net	(93.7)	(153.0)
Net Cash Provided by (Used in) Investing Activities	5,133.7	(21,500.3)
CASH FLOWS FROM FINANCING ACTIVITIES
Change in Deposits	(5,844.1)	23,956.5
Change in Federal Funds Purchased	(260.0)	3,817.7
Change in Securities Sold under Agreements to Repurchase	55.8	(455.6)
Change in Short-Term Other Borrowings	1,420.3	(778.0)
Redemption of Preferred Stock - Series C	0.0	(400.0)
Treasury Stock Purchased	(135.6)	(296.8)
Net Proceeds from Stock Options	8.7	8.8
Cash Dividends Paid on Common Stock	(145.9)	(147.1)
Cash Dividends Paid on Preferred Stock	(4.7)	(5.8)
Other Financing Activities, net	(0.1)	8.3
Net Cash (Used in) Provided by Financing Activities	(4,905.6)	25,708.0
Effect of Foreign Currency Exchange Rates on Cash	(101.5)	(148.4)
Change in Cash and Due from Banks	194.9	1,374.0
Cash and Due from Banks at Beginning of Period	4,389.5	4,459.2
Cash and Due from Banks at End of Period	4,584.4	5,833.2
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest Paid	2.2	126.7
Income Taxes Paid	30.8	72.6
Transfers from Loans to OREO	$ 3.3	$ (0.2)