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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 | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) credit | Mar. 31, 2019 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Dec. 31, 2018 USD ($) fund
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |  |
Investments in tax credit and other investments, net | $ 211,603,000 |  |  | $ 211,603,000 |  | $ 231,635,000
Accrued expenses and other liabilities — Unfunded commitments | 69,649,000 |  |  | 69,649,000 |  | 80,228,000
Amortization expense of tax credit and other investments | 16,833,000 |  | $ 20,789,000 | 58,477,000 | $ 58,670,000 |
Unrealized gains (losses) recognized on marketable equity securities held | 188,000 |  | (185,000) | 955,000 | (798,000) |
Tax credit investments |  |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |  |
Marketable equity securities | 31,700,000 |  |  | 31,700,000 |  | 31,200,000
Amortization of tax credit and other investments |  |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |  |
Pre-tax impairment charge | 1,700,000 |  | $ 0 | 11,600,000 | $ 0 |
DC Solar Tax Credit Investments |  |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |  |
Investments in tax credit and other investments, net |  |  |  |  |  | $ 7,000,000.0
Number of solar energy tax credit funds | fund |  |  |  |  |  | 4
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 |  |  |  |
Impaired CRA investments other than DC Solar | Amortization of tax credit and other investments |  |  |  |  |  |
Investments in Tax Credit and Other Investments, Net [Line Items] |  |  |  |  |  |
Pre-tax impairment charge | $ 1,700,000 |  |  |  |  |
Number of impaired tax credit investments | credit | 2 |  |  |  |  |

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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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