amortized cost, fair value and tax equivalent yield of securities, by maturity (Details) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)
U S Government Agency Notes 1 [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 2,497
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 2,545
Receivable with Imputed Interest, Effective Yield (Interest Rate)	348.00%
U S Government Agency Notes Total [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 2,497
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 2,545
Receivable with Imputed Interest, Effective Yield (Interest Rate)	348.00%
U S States And Political Subdivisions 2 [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 2,731
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 2,910
Receivable with Imputed Interest, Effective Yield (Interest Rate)	259.00%
U S States And Political Subdivisions 3 [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 23,100
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 24,707
Receivable with Imputed Interest, Effective Yield (Interest Rate)	302.00%
US States and Political Subdivisions Debt Securities [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 25,831
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 27,617
Receivable with Imputed Interest, Effective Yield (Interest Rate)	298.00%
Corporate Debt Securities [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 8,750
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 8,916
Receivable with Imputed Interest, Effective Yield (Interest Rate)	522.00%
US Government Agencies Debt Securities [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 57,532
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 59,333
Receivable with Imputed Interest, Effective Yield (Interest Rate)	200.00%
Available-for-sale Securities [Member]
Open Option Contracts Written [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	$ 94,610
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	$ 98,411
Receivable with Imputed Interest, Effective Yield (Interest Rate)	261.00%

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=120252992&loc=SL120269850-112803

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
-Topic 320
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-Section 50
-Paragraph 2
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27198-111563

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27198-111563

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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