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Securities - Additional Information (Details) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2020 USD ($) Investment | Jun. 30, 2019 USD ($) | Jun. 30, 2020 USD ($) Investment | Jun. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) Investment
Schedule of Investments [Line Items] |  |  |  |  |  |
Federal Home Loan Bank stock, at cost | $ | [1] | $ 668,698,000 |  | $ 668,698,000 |  | $ 647,562,000
Equity Securities, FV-NI, Unrealized Gain | $ |  | $ 902,000 | $ 457,000 | $ 687,000 | $ 1,200,000 |
Collateralized Mortgage Obligations |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  | 7 |  | 7 |  | 3
Capital Trust Notes |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  | 5 |  | 5 |  | 5
Asset-backed Securities |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  | 7 |  | 7 |  | 3
Corporate Bonds |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  | 3 |  | 3 |  | 2
Municipal Bonds |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  | 1 |  | 1 |  | 1
US Government Agencies Securities |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  |  |  |  |  | 7
Mortgage-related Securities |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  |  |  |  |  | 3
Mutual Fund |  |  |  |  |  |
Schedule of Investments [Line Items] |  |  |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  |  |  |  |  | 1
[1] | Carrying value and estimated fair value are at cost.

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- Definition Number of Securities, Continuous Unrealized Loss Position More Than Twelve Months + References No definition available. + Details
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- Definition Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714 + Details
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- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
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