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Loans and Allowances for Credit Losses, Troubled Debt Restructurings (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Troubled Debt Restructuring, Recorded Investment | $ 132.0 | $ 166.0
Troubled Debt Restructuring, Performing in Accordance With Modified Terms | 57.0 | 71.0
Troubled Debt Restructuring, Charge-offs | 18.6 | 16.1
Troubled Debt Restructurings, Recorded Balance Modified During The Period | 37.0 | 75.0
Residential Mortgage [Member] | Accruing [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |
Troubled Debt Restructuring, Recorded Investment | $ 92.0 | $ 86.0

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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 Amount, after troubled debt restructuring, of modified financing receivable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524 + Details
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- Definition Amount of financing receivable modified as troubled debt restructuring. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524 Reference 2: 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=118939409&loc=d3e18845-111554 + Details
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- Definition Reflects the amount of the write-down related to a troubled debt restructuring. + 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=118939409&loc=d3e18845-111554 + Details
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