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Qualified Affordable Housing (Details) | 12 Months Ended
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Dec. 31, 2017 USD ($) commitment | Dec. 31, 2016 USD ($) commitment | Dec. 31, 2015 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |
Investments in qualified affordable housing projects | $ 9,000,000 | $ 11,700,000 |
Number of open commitments to fund future investments in qualified affordable housing | commitment | 1 | 0 |
Open commitments to fund future investments qualified affordable housing projects | $ 800,000 | $ 0 |
Tax credits to offset amortization expense of investments in affordable housing projects | 3,400,000 | 3,700,000 | $ 4,000,000
Noninterest Expense |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Amortization expense of investments in qualified affordable housing projects | $ 3,000,000 | $ 3,300,000 | $ 3,600,000

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- Definition Qualified Affordable Housing Project Investments, Commitment, Number + References No definition available. + Details
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- Definition Amount of affordable housing tax credits and other tax benefits recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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- Definition Amount of investment in qualified affordable housing projects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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- Definition Amount of amortization expense of investment in qualified affordable housing projects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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- Definition Amount of commitment or contingent commitments to qualified affordable housing project investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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