Loans and Allowance - Impaired financing receivables (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Recorded Investment with specific reserves	$ 40,000	$ 26,000
Unpaid Principal Balance with specific reserves	40,000	41,000
Interest Income Recognized with specific reserves	1,000	2,000
Specific Reserve with specific reserves	11,000	15,000
Recorded Investment	50,000	50,000
Recorded Investment with no specific reserve	4,568,000	4,627,000
Unpaid Principal Balance with no specific reserve	4,623,000	5,396,000
Interest Income Recognized with no specific reserve	34,000	109,000
Specific Reserve	11,000
Average Recorded Investment with no specific reserve	5,935,000	5,895,000
Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment with specific reserves	40,000	26,000
Unpaid Principal Balance with specific reserves	40,000	41,000
Interest Income Recognized with specific reserves	1,000	2,000
Specific Reserve with specific reserves	11,000	15,000
Recorded Investment	50,000	50,000
Recorded Investment with no specific reserve	92,000	96,000
Unpaid Principal Balance with no specific reserve	92,000	96,000
Interest Income Recognized with no specific reserve		8,000
Average Recorded Investment with no specific reserve	116,000	122,000
Indirect
Financing Receivable, Impaired [Line Items]
Interest Income Recognized with specific reserves		6,000
Recorded Investment with no specific reserve	136,000	123,000
Unpaid Principal Balance with no specific reserve	136,000	123,000
Specific Reserve	11,000
Average Recorded Investment with no specific reserve	152,000
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	3,627,000	3,680,000
Unpaid Principal Balance with no specific reserve	3,627,000	3,680,000
Interest Income Recognized with no specific reserve	31,000	81,000
Average Recorded Investment with no specific reserve	3,749,000	3,845,000
Residential Real estate
Financing Receivable, Impaired [Line Items]
Recorded Investment with no specific reserve	713,000	728,000
Unpaid Principal Balance with no specific reserve	768,000	1,497,000
Interest Income Recognized with no specific reserve	3,000	14,000
Average Recorded Investment with no specific reserve	$ 1,918,000	$ 1,928,000

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953423-111524

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+ References

No definition available.

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Amount of allowance for credit losses related to recorded investment.

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Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

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Amount of interest income, recognized on cash basis, on financing receivables, for which there is no related allowance for credit losses and are recognized as impaired.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524

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- Definition

Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

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Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524

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Amount of interest income on financing receivables, for which there is a related allowance for credit losses, recognized on a cash-basis method of accounting that the financing receivables were impaired.

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Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

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