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Debt Securities Available-for-Sale - Comparative Summary of Mortgage-Backed Securities and Other Securities Available-for-Sale) (Details) - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | $ 1,046,738 | $ 1,131,970
Gross unrealized gains | 17,096 | 9,374
Gross unrealized losses | 2,391 | 2,992
Debt securities available-for-sale | 1,061,443 | 1,138,352
Real estate mortgage investment conduits (REMICs) |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 918,817 | 967,949
Gross unrealized gains | 16,676 | 8,157
Gross unrealized losses | 995 | 2,979
Debt securities available-for-sale | 934,498 | 973,127
Other debt obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 127,921 | 164,021
Gross unrealized gains | 420 | 1,217
Gross unrealized losses | 1,396 | 13
Debt securities available-for-sale | 126,945 | 165,225
GSE | Pass-through Certificates |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 300,610 | 324,080
Gross unrealized gains | 10,340 | 6,081
Gross unrealized losses | 81 | 754
Debt securities available-for-sale | 310,869 | 329,407
GSE | Real estate mortgage investment conduits (REMICs) |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 618,156 | 643,816
Gross unrealized gains | 6,336 | 2,076
Gross unrealized losses | 912 | 2,225
Debt securities available-for-sale | 623,580 | 643,667
Non-GSE | Real estate mortgage investment conduits (REMICs) |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 51 | 53
Gross unrealized gains | 0 | 0
Gross unrealized losses | 2 | 0
Debt securities available-for-sale | 49 | 53
Municipal bonds | Other debt obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 278 | 296
Gross unrealized gains | 1 | 3
Gross unrealized losses | 0 | 0
Debt securities available-for-sale | 279 | 299
Corporate bonds | Other debt obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 127,643 | 163,725
Gross unrealized gains | 419 | 1,214
Gross unrealized losses | 1,396 | 13
Debt securities available-for-sale | $ 126,666 | $ 164,926

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- Definition Amount, before tax, of unrealized gain 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 (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- 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=118939692&loc=d3e27161-111563 + Details
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