Revenue from Contracts with Clients (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 975.5	$ 939.2	$ 2,859.9	$ 2,819.8
Security commissions and trading income	29.1	21.9	75.8	75.2
Other operating income	45.1	20.9	113.0	87.1
Securities Commissions and Trading Income
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	23.5	19.7	64.3	66.0
Other Operating Income
Disaggregation of Revenue [Line Items]
Trust, Investment and Other Servicing Fees	$ 10.5	$ 10.4	$ 30.9	$ 33.3

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.

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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