Loans (Purchased Credit Impaired Loans With Deteriorated Credit Quality) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	$ 3,065.7	$ 3,685.0
Carrying Value	2,134.1	2,571.6
Allowance for Loan Losses	45.1	47.3
Commercial Banking \| Commercial Finance
Financing Receivable, Impaired [Line Items]
Allowance for Loan Losses	21.3	25.5
Commercial Banking \| Real Estate Finance
Financing Receivable, Impaired [Line Items]
Allowance for Loan Losses	0.4	4.0
PCI Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,870.2	3,440.7
Carrying Value	1,961.4	2,349.8
Allowance for Loan Losses	19.1	13.6
PCI Loans \| Commercial Banking \| Commercial Finance
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	16.4	70.0
Carrying Value	10.6	42.7
Allowance for Loan Losses	0.7	2.4
PCI Loans \| Commercial Banking \| Real Estate Finance
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	60.1	108.1
Carrying Value	45.1	70.5
Allowance for Loan Losses	7.0	4.9
PCI Loans \| Consumer Banking \| Other Consumer Banking
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	3.0	3.7
Carrying Value	2.2	2.8
Allowance for Loan Losses	0.0	0.0
PCI Loans \| Consumer Banking \| LCM
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,790.7	3,258.9
Carrying Value	1,903.5	2,233.8
Allowance for Loan Losses	$ 11.4	$ 6.3

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- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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