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Investment Securities - Held-to-Maturity Amortized Cost and Fair Value (Details) - USD ($) | Mar. 31, 2021 | Dec. 31, 2020
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Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | $ 151,970,000 | $ 109,036,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 151,970,000 | 109,036,000
Held-to-maturity, gross unrealized gains | 4,975,000 | 6,149,000
Held-to-maturity, gross unrealized losses | (189,000) | 0
Held to maturity, fair value | 156,756,000 | 115,185,000
Accrued interest | 295,000 | 366,000
MBS pass-through securities issued by FHLMC and FNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 78,227,000 | 65,579,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 78,227,000 | 65,579,000
Held-to-maturity, gross unrealized gains | 3,283,000 | 3,924,000
Held-to-maturity, gross unrealized losses | 0 | 0
Held to maturity, fair value | 81,510,000 | 69,503,000
CMOs issued by FHLMC |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 30,207,000 | 27,201,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 30,207,000 | 27,201,000
Held-to-maturity, gross unrealized gains | 1,105,000 | 1,441,000
Held-to-maturity, gross unrealized losses | (189,000) | 0
Held to maturity, fair value | 31,123,000 | 28,642,000
CMOs issued by FNMA |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 7,305,000 | 8,042,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 7,305,000 | 8,042,000
Held-to-maturity, gross unrealized gains | 347,000 | 363,000
Held-to-maturity, gross unrealized losses | 0 | 0
Held to maturity, fair value | 7,652,000 | 8,405,000
SBA-backed securities |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 5,699,000 | 6,547,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 5,699,000 | 6,547,000
Held-to-maturity, gross unrealized gains | 227,000 | 400,000
Held-to-maturity, gross unrealized losses | 0 | 0
Held to maturity, fair value | 5,926,000 | 6,947,000
Debentures of government- sponsored agencies |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 29,950,000 |
Allowance for Credit Losses | 0 |
Net Carrying Amount | 29,950,000 |
Held-to-maturity, gross unrealized gains | 0 |
Held-to-maturity, gross unrealized losses | 0 |
Held to maturity, fair value | 29,950,000 |
Obligations of state and political subdivisions |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 582,000 | 1,667,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 582,000 | 1,667,000
Held-to-maturity, gross unrealized gains | 13,000 | 21,000
Held-to-maturity, gross unrealized losses | 0 | 0
Held to maturity, fair value | $ 595,000 | $ 1,688,000

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- Definition Amount, before allowance for credit loss, of accrued interest on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 3B -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL120267963-210447 + Details
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