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Investments in Qualified Affordable Housing Partnerships, Tax Credit and Other Investments, Net and Variable Interest Entities (Investments in Tax Credit and Other Investments, Net) (Details) | 3 Months Ended | 6 Months Ended |
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Jun. 30, 2019 USD ($) fund | Jun. 30, 2018 USD ($) | Jun. 30, 2019 USD ($) fund | Jun. 30, 2018 USD ($) | Dec. 31, 2018 USD ($)
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |
Investments in tax credit and other investments, net | $ 210,387,000 |  | $ 210,387,000 |  | $ 231,635,000
Accrued expenses and other liabilities — Unfunded commitments | 73,369,000 |  | 73,369,000 |  | 80,228,000
Amortization expense of tax credit and other investments | 16,739,000 | $ 20,481,000 | 41,644,000 | $ 37,881,000 |
Unrealized gains (losses) recognized on marketable equity securities held | 375,000 | $ (159,000) | 767,000 | $ (613,000) |
Pre-tax impairment charge | 2,900,000 |  | 9,900,000 |  |
Tax credit investments |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |
Marketable equity securities | $ 31,400,000 |  | $ 31,400,000 |  | 31,200,000
DC Solar Tax Credit Investments |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |
Number of solar energy tax credit funds | fund | 4 |  | 4 |  |
Investments in tax credit and other investments, net |  |  |  |  | 7,000,000.0
DC Solar Tax Credit Investments | Accrued expenses and other liabilities - unfunded commitments |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |
Accrued expenses and other liabilities — Unfunded commitments | $ 0 |  | $ 0 |  | $ 0
DC Solar Tax Credit Investments | Amortization of tax credit and other investments |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |
Pre-tax impairment charge | $ 7,000,000.0 |  |  |  |

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- Definition Represents the net amount of investments in the projects, excluding affordable housing projects, that qualify for Community Reinvestment Act (CRA) credits or other types of tax credits. + References No definition available. + Details
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- Definition [Line Items] for Investments in Tax Credit and Other Investments, Net [Table] + References No definition available. + Details
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- Definition Amortization of investments in projects that qualify for Community Reinvestment Act ("CRA") and other tax credits, included as a component of noninterest expense. + References No definition available. + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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