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Securities - Additional Information (Details) | 12 Months Ended
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Dec. 31, 2020 USD ($) Investment | Dec. 31, 2019 USD ($) Investment | Dec. 31, 2018 USD ($)
Schedule of Investments [Line Items] |  |  |  |
Federal Home Loan Bank stock, at cost | $ | [1] | $ 714,005,000 | $ 647,562,000 |
Net gains on equity securities | $ |  | $ 582,000 | $ 2,300,000 | $ 2,000,000.0
Collateralized Mortgage Obligations |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Number of investment securities designated as having a continuous loss position for twelve months or more |  | 4 | 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 |
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 | 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 | 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 |
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 Amount of unrealized and realized gain (loss) 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/2009/role/commonPracticeRef -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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