Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	$ 1,199.0	$ 1,032.5	$ 973.8
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Investment Security Losses, net	1.6	3.2	0.3
Amortization and Accretion of Securities and Unearned Income, net	105.0	100.9	53.3
Provision for Credit Losses	(28.0)	(26.0)	(43.0)
Depreciation on Buildings and Equipment	101.2	89.2	90.4
Amortization of Intangibles	11.4	8.8	10.9
Change in Accrued Income Taxes	36.2	(129.0)	206.8
Pension Plan Contributions	(14.5)	(12.8)	(21.1)
Deferred Income Tax Provision	(76.1)	(175.8)	(146.2)
Change in Receivables	(119.3)	(129.2)	(16.2)
Change in Interest Payable	10.7	(0.1)	(8.2)
Change in Collateral With Derivative Counterparties, net	486.2	(180.4)	801.4
Other Operating Activities, net	(302.1)	653.4	(318.1)
Net Cash Provided by Operating Activities	1,720.4	1,510.0	1,834.4
CASH FLOWS FROM INVESTING ACTIVITIES
Net Change in Federal Funds Sold and Securities Purchased under Agreements to Resell	678.9	(372.9)	(549.8)
Change in Interest-Bearing Deposits with Banks	(467.7)	1,906.1	284.9
Net Change in Federal Reserve and Other Central Bank Deposits	(12,748.7)	(4,124.2)	558.6
Purchases of Securities – Held to Maturity	(11,955.2)	(8,573.2)	(8,075.5)
Proceeds from Maturity and Redemption of Securities – Held to Maturity	9,924.8	4,026.5	6,628.3
Purchases of Securities – Available for Sale	(9,780.0)	(14,741.9)	(11,490.3)
Proceeds from Sale, Maturity and Redemption of Securities – Available for Sale	10,103.4	11,317.3	8,576.1
Change in Loans and Leases	1,451.0	(471.0)	(1,581.0)
Purchases of Buildings and Equipment	(91.6)	(111.3)	(98.5)
Purchases and Development of Computer Software	(381.2)	(362.1)	(335.0)
Change in Client Security Settlement Receivables	(592.6)	1,105.0	(605.0)
Acquisition of a Subsidiary, Net of Cash Received	(188.5)	(16.9)	0.0
Other Investing Activities, net	25.8	226.5	(212.9)
Net Cash Used in Investing Activities	(14,021.6)	(10,192.1)	(6,900.1)
CASH FLOWS FROM FINANCING ACTIVITIES
Change in Deposits	8,523.6	6,737.4	8,105.7
Change in Federal Funds Purchased	2,081.2	(146.7)	(581.4)
Change in Securities Sold under Agreements to Repurchase	360.5	(72.9)	(338.5)
Change in Short-Term Other Borrowings	967.7	1,073.5	2,312.8
Proceeds from Senior Notes and Long-Term Debt	350.0	0.0	0.0
Repayments of Senior Notes and Long-Term Debt	(208.7)	(6.7)	(231.0)
Proceeds from Issuance of Preferred Stock - Series D	0.0	493.5	0.0
Treasury Stock Purchased	(523.1)	(411.1)	(496.9)
Net Proceeds from Stock Options	108.0	233.8	94.0
Cash Dividends Paid on Common Stock	(356.8)	(333.0)	(321.4)
Cash Dividends Paid on Preferred Stock	(49.8)	(23.4)	(27.0)
Other Financing Activities, net	0.1	(7.5)	17.8
Net Cash Provided by Financing Activities	11,252.7	7,536.9	8,534.1
Effect of Foreign Currency Exchange Rates on Cash	234.6	58.7	(70.9)
(Decrease) Increase in Cash and Due from Banks	(813.9)	(1,086.5)	3,397.5
Cash and Due from Banks at Beginning of Year	5,332.0	6,418.5	3,021.0
Cash and Due from Banks at End of Year	4,518.1	5,332.0	6,418.5
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest Paid	328.8	181.6	161.6
Income Taxes Paid	441.2	754.2	390.0
Transfers from Loans to OREO	8.2	14.2	13.0
Computer Software
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Amortization of Intangibles	309.1	275.3	250.3
Other Intangible Assets
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Amortization of Intangibles	$ 11.4	$ 8.8	$ 10.9