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Loans and Allowances for Credit Losses, Troubled Debt Restructurings (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Troubled Debt Restructuring, Recorded Investment | $ 171.0 | $ 129.0 | $ 171.0 | $ 129.0 | $ 126.0
Troubled Debt Restructuring, Performing in Accordance With Modified Terms | 83.0 | 60.0 | 83.0 | 60.0 | 48.0
Financing Receivable, Modifications, Post-Modification Recorded Investment | 31.0 | 11.0 | 76.0 | 53.0 |
Troubled Debt Restructuring, Charge-offs | 4.5 | 4.4 | 10.2 | 4.4 |
Permanent mortgages guaranteed by US government agencies [Member] | Accruing [Member] | Residential mortgage [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Troubled Debt Restructuring, Recorded Investment | $ 83.0 | $ 69.0 | $ 83.0 | $ 69.0 | $ 74.0

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- Definition Represents the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructuring and are performing according to modified terms. + References No definition available. + Details
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- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
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- Definition The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554 + Details
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