Reporting Segments (Results of Reporting Segments) (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($) Segment	Mar. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reporting segments \| Segment	2
Trust, Investment and Other Servicing Fees	$ 928.9	$ 937.7
Foreign Exchange Trading Income	66.2	78.5
Other Noninterest Income	63.8	75.8
Net Interest Income	429.8	392.7
Revenue	1,488.7	1,484.7
Provision for Credit Losses	0.0	(3.0)
Noninterest Expense	1,028.7	995.3
Income before Income Taxes	460.0	492.4
Provision for Income Taxes	112.9	110.8
Net Income	$ 347.1	$ 381.6
Percentage of Consolidated Net Income	100.00%	100.00%
Average Assets	$ 119,416.7	$ 124,493.3
FTE adjustments	7.8	8.7
Corporate & Institutional Services
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	535.2	544.3
Foreign Exchange Trading Income	59.7	62.4
Other Noninterest Income	43.4	46.6
Net Interest Income	234.8	229.4
Revenue	873.1	882.7
Provision for Credit Losses	(1.1)	(3.9)
Noninterest Expense	648.0	585.6
Income before Income Taxes	226.2	301.0
Provision for Income Taxes	53.6	66.8
Net Income	$ 172.6	$ 234.2
Percentage of Consolidated Net Income	50.00%	61.00%
Average Assets	$ 90,351.7	$ 83,637.0
Wealth Management
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	393.7	393.4
Foreign Exchange Trading Income	6.5	1.2
Other Noninterest Income	25.5	25.7
Net Interest Income	195.0	198.8
Revenue	620.7	619.1
Provision for Credit Losses	1.1	0.9
Noninterest Expense	379.9	365.7
Income before Income Taxes	239.7	252.5
Provision for Income Taxes	60.8	62.4
Net Income	$ 178.9	$ 190.1
Percentage of Consolidated Net Income	51.00%	50.00%
Average Assets	$ 29,065.0	$ 26,108.0
Treasury and Other
Segment Reporting Information [Line Items]
Trust, Investment and Other Servicing Fees	0.0	0.0
Foreign Exchange Trading Income	0.0	14.9
Other Noninterest Income	(5.1)	3.5
Net Interest Income	0.0	(35.5)
Revenue	(5.1)	(17.1)
Provision for Credit Losses	0.0	0.0
Noninterest Expense	0.8	44.0
Income before Income Taxes	(5.9)	(61.1)
Provision for Income Taxes	(1.5)	(18.4)
Net Income	$ (4.4)	$ (42.7)
Percentage of Consolidated Net Income	(1.00%)	(11.00%)
Average Assets	$ 0.0	$ 14,748.3

Income (Loss) Before Income Taxes Including Fully Taxable-Equivalent Adjustment

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Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment

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Interest Revenue (Expense), Net Including Fully Taxable Equivalent Adjustment

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Percentage of Consolidated Net Income

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The sum of the periodic provision charged or credited to earnings, based on an assessment of uncollectability from the counterparty on account of loan, lease or other credit losses, to reduce these accounts to the amount that approximates their net realizable value.

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Revenue Including Fully Taxable Equivalent Adjustment

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Segment Reporting Information, Consolidated Average Assets

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Represents Fully Taxable-Equivalent Adjustment (FTE). Net interest income stated on an FTE basis is a non-GAAP financial measure that facilitates the analysis of asset yields and provides a clearer indication of net interest margins for comparative purposes.

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Revenue recognized in the period for trust, investment management, custody, securities lending, and other servicing fees. Fees are based generally on the market value of assets held in custody, managed and serviced; the volume of transactions; securities lending volume and spreads; and fees for other services rendered.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Total aggregate amount of all noninterest expense.

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Represents the total of noninterest income derived from certain activities and assets including (for example): (1) venture capital investments; (2) bank owned life insurance; (3) foreign currency transactions; and (4) mortgage servicing rights.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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