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Fair Value Measurements - Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available-for-sale	$ 1,037,489	$ 1,138,352
Trading securities	10,094	11,222
Impaired loans	6,706	4,942
Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities available-for-sale	1,037,489	1,138,352
Trading securities	10,094	11,222
Equity securities	214	250
Total	1,047,797	1,149,824
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	943,209	973,127
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	289,153	329,407
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	654,009	643,667
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	47	53
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	254	299
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	94,026	164,926
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	94,280	165,225
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	10,094	11,222
Equity securities	214	250
Total	10,308	11,472
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	1,037,489	1,138,352
Trading securities	0	0
Equity securities	0	0
Total	1,037,489	1,138,352
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	943,209	973,127
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	289,153	329,407
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	654,009	643,667
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	47	53
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	254	299
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	94,026	164,926
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	94,280	165,225
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	6,706	4,942
Measured on a non-recurring basis | Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	6,692	4,927
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	6,125	4,871
Measured on a non-recurring basis | Real Estate | One-to-Four Family
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	517
Measured on a non-recurring basis | Real Estate | Multifamily
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	22	26
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	28	30
Measured on a non-recurring basis | Commercial and Industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	14	15
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
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	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
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	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	6,706	4,942
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	6,692	4,927
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	6,125	4,871
Measured on a non-recurring basis | Significant Unobservable Inputs (Level 3) | Real Estate | One-to-Four Family
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	517
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	22	26
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	28	30
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	$ 14	$ 15

X

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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).

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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