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Investment Securities Available For Sale - Narrative (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items] |  |  |
Proceeds from sale of investment securities, available-for-sale | $ 98,000,000.0 | $ 26,900,000 | $ 107,100,000
Net realized gain (loss) on investment securities available for sale | $ 21,800,000 | $ (12,300,000) | (100,000)
Contractual maturities (up to) | 40 years |  |
Available for sale securities portfolio, weighted average life | 5 years | 5 years 8 months 12 days |
Gross unrealized losses | $ (7,591,000) | $ (40,126,000) |
Other-than-temporary Impairment loss | 0 | 0 | $ 0
Agency RMBS |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Gross unrealized losses | (7,454,000) | (38,284,000) |
Non-Agency RMBS |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Gross unrealized losses | (13,000.0) | (1,466,000) |
CMBS |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Gross unrealized losses | $ (124,000) | $ (376,000) |

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- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27357-111563 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922888-210455 + Details
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