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Investment Securities - Held-to-Maturity Amortized Cost and Fair Value (Details) - USD ($) | Sep. 30, 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 | $ 196,801,000 | $ 109,036,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 196,801,000 | 109,036,000
Held-to-maturity, gross unrealized gains | 4,415,000 | 6,149,000
Held-to-maturity, gross unrealized losses | (164,000) | 0
Held to maturity, fair value | 201,052,000 | 115,185,000
Accrued interest | 451,000 | 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 | 70,085,000 | 65,579,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 70,085,000 | 65,579,000
Held-to-maturity, gross unrealized gains | 2,828,000 | 3,924,000
Held-to-maturity, gross unrealized losses | (38,000) | 0
Held to maturity, fair value | 72,875,000 | 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 | 42,275,000 | 27,201,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 42,275,000 | 27,201,000
Held-to-maturity, gross unrealized gains | 1,114,000 | 1,441,000
Held-to-maturity, gross unrealized losses | (95,000) | 0
Held to maturity, fair value | 43,294,000 | 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 | 5,598,000 | 8,042,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 5,598,000 | 8,042,000
Held-to-maturity, gross unrealized gains | 163,000 | 363,000
Held-to-maturity, gross unrealized losses | 0 | 0
Held to maturity, fair value | 5,761,000 | 8,405,000
SBA-backed securities |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 4,841,000 | 6,547,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 4,841,000 | 6,547,000
Held-to-maturity, gross unrealized gains | 290,000 | 400,000
Held-to-maturity, gross unrealized losses | 0 | 0
Held to maturity, fair value | 5,131,000 | 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 | 51,470,000 |
Allowance for Credit Losses | 0 |
Net Carrying Amount | 51,470,000 |
Held-to-maturity, gross unrealized gains | 0 |
Held-to-maturity, gross unrealized losses | 0 |
Held to maturity, fair value | 51,470,000 |
Obligations of state and political subdivisions |  |
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items] |  |
Held to maturity, amortized cost | 22,532,000 | 1,667,000
Allowance for Credit Losses | 0 | 0
Net Carrying Amount | 22,532,000 | 1,667,000
Held-to-maturity, gross unrealized gains | 20,000 | 21,000
Held-to-maturity, gross unrealized losses | (31,000) | 0
Held to maturity, fair value | $ 22,521,000 | $ 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=124255953&loc=SL120267963-210447 + Details
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