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Fair Value Measurements - Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | $ 894,272 | $ 808,031
Trading securities | 9,759 | 8,968
Impaired loans | 5,216 | 5,697
Measured on a recurring basis |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 894,272 | 808,031
Trading securities | 9,759 | 8,968
Equity securities | 414 | 237
Total | 904,445 | 817,236
Measured on a recurring basis | Mortgage-backed securities: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 668,086 | 565,009
Measured on a recurring basis | Pass-through certificates, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 404,537 | 314,788
Measured on a recurring basis | REMICs, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 263,492 | 250,163
Measured on a recurring basis | Non-GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 57 | 58
Measured on a recurring basis | Municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 274 | 273
Measured on a recurring basis | Corporate bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 225,912 | 242,749
Measured on a recurring basis | Other debt obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 226,186 | 243,022
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Trading securities | 9,759 | 8,968
Equity securities | 414 | 237
Total | 10,173 | 9,205
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-backed securities: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pass-through certificates, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | REMICs, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other debt obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 894,272 | 808,031
Trading securities | 0 | 0
Equity securities | 0 | 0
Total | 894,272 | 808,031
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 668,086 | 565,009
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Pass-through certificates, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 404,537 | 314,788
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | REMICs, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 263,492 | 250,163
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Non-GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 57 | 58
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 274 | 273
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Corporate bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 225,912 | 242,749
Measured on a recurring basis | Significant Other Observable Inputs (Level 2) | Other debt obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 226,186 | 243,022
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Trading securities | 0 | 0
Equity securities | 0 | 0
Total | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Mortgage-backed securities: |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Pass-through certificates, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | REMICs, GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Non-GSE |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Corporate bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a recurring basis | Significant Unobservable Inputs (Level 3) | Other debt obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Debt securities available-for-sale | 0 | 0
Measured on a non-recurring basis |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total | 5,216 | 5,697
Measured on a non-recurring basis | Real Estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 5,201 | 5,679
Measured on a non-recurring basis | Real Estate | Commercial real estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 4,679 | 4,847
Measured on a non-recurring basis | Real Estate | One-to-four family residential mortgage |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 461 | 765
Measured on a non-recurring basis | Real Estate | Multifamily |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 35 | 39
Measured on a non-recurring basis | Real Estate | Home equity and lines of credit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 26 | 28
Measured on a non-recurring basis | Commercial and Industrial |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 15 | 18
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total | 0 | 0
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Estate | Commercial real estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Estate | One-to-four family residential mortgage |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Estate | Multifamily |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Estate | Home equity and lines of credit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial and Industrial |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) | Real Estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) | Real Estate | Commercial real estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) | Real Estate | One-to-four family residential mortgage |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) | Real Estate | Multifamily |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) | Real Estate | Home equity and lines of credit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Other Observable Inputs (Level 2) | Commercial and Industrial |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 0 | 0
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total | 5,216 | 5,697
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Real Estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 5,201 | 5,679
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Real Estate | Commercial real estate |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 4,679 | 4,847
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Real Estate | One-to-four family residential mortgage |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 461 | 765
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Real Estate | Multifamily |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 35 | 39
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Real Estate | Home equity and lines of credit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | 26 | 28
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Commercial and Industrial |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Impaired loans | $ 15 | $ 18

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