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Debt Securities Available-for-Sale - Gross Unrealized Losses on Mortgage-Backed Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Unrealized losses, less than 12 months | $ 302 | $ 2,376
Estimated Fair value, less than 12 months | 106,717 | 302,921
Unrealized losses, 12 months or more | 7,812 | 11,361
Estimated Fair value, 12 months or more | 303,061 | 307,354
Unrealized losses, total | 8,114 | 13,737
Estimated fair value, total | 409,778 | 610,275
GSE | Pass-through Certificates |  |
Debt Securities, Available-for-sale [Line Items] |  |
Unrealized losses, less than 12 months | 170 | 404
Estimated Fair value, less than 12 months | 34,164 | 82,781
Unrealized losses, 12 months or more | 2,057 | 3,138
Estimated Fair value, 12 months or more | 96,411 | 100,109
Unrealized losses, total | 2,227 | 3,542
Estimated fair value, total | 130,575 | 182,890
GSE | Real estate mortgage investment conduits (REMICs) |  |
Debt Securities, Available-for-sale [Line Items] |  |
Unrealized losses, less than 12 months | 8 | 269
Estimated Fair value, less than 12 months | 19,136 | 46,921
Unrealized losses, 12 months or more | 5,464 | 7,710
Estimated Fair value, 12 months or more | 170,787 | 181,512
Unrealized losses, total | 5,472 | 7,979
Estimated fair value, total | 189,923 | 228,433
Non-GSE | Real estate mortgage investment conduits (REMICs) |  |
Debt Securities, Available-for-sale [Line Items] |  |
Unrealized losses, less than 12 months |  | 0
Estimated Fair value, less than 12 months |  | 0
Unrealized losses, 12 months or more | 1 | 1
Estimated Fair value, 12 months or more | 57 | 58
Unrealized losses, total | 1 | 1
Estimated fair value, total | 57 | 58
Corporate bonds | Other debt obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Unrealized losses, less than 12 months | 124 | 1,703
Estimated Fair value, less than 12 months | 53,417 | 173,219
Unrealized losses, 12 months or more | 290 | 512
Estimated Fair value, 12 months or more | 35,806 | 25,675
Unrealized losses, total | 414 | 2,215
Estimated fair value, total | $ 89,223 | $ 198,894

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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), in continuous unrealized loss position for more than 12 months. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + 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 continuous unrealized loss position for 12 months or longer. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + 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), in continuous unrealized loss position for less than 12 months. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
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