Revenue from Contracts with Clients (Revenue Disaggregation) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 955.5	$ 942.9	$ 1,884.4	$ 1,880.6
Foreign Exchange Trading Income	60.5	78.9	126.7	157.4
Treasury Management Fees	11.2	13.5	22.9	27.5
Security Commissions and Trading Income	23.4	26.1	46.7	53.3
Other Operating Income	38.9	31.4	67.9	66.2
Investment Security Losses, net	(0.3)	0.0	(0.5)	(0.2)
Total Other Noninterest Income	133.7	149.9	263.7	304.2
Total Noninterest Income	1,089.2	1,092.8	2,148.1	2,184.8
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	407.4	399.1	804.9	795.0
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	478.1	465.0	937.3	930.6
Securities Lending
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	22.0	30.4	44.8	56.6
Other
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 48.0	$ 48.4	$ 97.4	$ 98.4

Other Noninterest Income

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Revenues earned for buying and selling securities on behalf of clients and other fees including fees earned for transitioning assets between investment firms, fees earned for buying and selling interest rate protection products, and other fees.

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Fees earned from treasury management activities including disbursements and receivables management, funds transfer, and online reporting.

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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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Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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The total amount of noninterest income which may be derived from: (1) fees and commissions; (2) premiums earned; (3) insurance policy charges; (4) the sale or disposal of assets; and (5) other sources not otherwise specified.

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The total amount of other operating income, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operation.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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