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Debt Securities Available-for-Sale - Narrative (Details) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 USD ($) security | Mar. 31, 2018 USD ($) | Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt securities, available-for-sale, restricted | $ 484,700,000 |  |
Proceeds from sale of debt securities available-for-sale | 29,163,000 | $ 19,508,000 |
Debt securities, available-for-sale, realized gain | 155,000 | 60,000 |
Debt securities, available-for-sale, realized loss | 0 | 5,000 |
Debt securities, trading, realized gain (loss) | 1,100,000 | 106,000 |
Debt securities available-for-sale | 894,272,000 |  | $ 808,031,000
Gross unrealized losses | 8,114,000 |  | 13,737,000
Other-than-temporary impairment loss, debt securities, available for sale, recognized in earnings | $ 0 | $ 0 |
Real Estate Mortgage Investment Conduits (REMICs) | GSE | Pass Through |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of debt securities, unrealized loss position longer than 12 months | security | 50 |  |
Real Estate Mortgage Investment Conduits (REMICs) | GSE | Non Pass Through |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of debt securities, unrealized loss position less than 12 months | security | 1 |  |
Number of debt securities, unrealized loss position longer than 12 months | security | 45 |  |
Real Estate Mortgage Investment Conduits (REMICs) | Non-GSE |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of debt securities, unrealized loss position longer than 12 months | security | 1 |  |
Real Estate Mortgage Investment Conduits (REMICs) | Municipal bonds |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of debt securities, unrealized loss position longer than 12 months | security | 7 |  |
Real Estate Mortgage Investment Conduits (REMICs) | Corporate bonds |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of debt securities, unrealized loss position less than 12 months | security | 8 |  |
Pass-through Certificates | GSE |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt securities available-for-sale | $ 404,537,000 |  | 314,788,000
Gross unrealized losses | $ 2,227,000 |  | $ 3,542,000
Pass-through Certificates | GSE | Pass Through |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of debt securities, unrealized loss position less than 12 months | security | 5 |  |
Non-Investment Grade | Debt securities | Corporate bonds |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of securities | security | 1 |  |
Debt securities available-for-sale | $ 5,000,000 |  |
Gross unrealized losses | $ 13,000 |  |

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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- Definition Amount of 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/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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- Definition Amount of realized gain 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/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
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- Definition Amount of restricted 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/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
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