Loans, Allowance for Credit Losses and Impaired Loans - Impaired loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserves - Recorded Investment	$ 4,309	$ 4,457
Impaired loans with specific reserves - Unpaid Principal Balance	4,347	4,457
Impaired loans with specific reserves - Interest Income Recognized	80	313
Impaired loans with specific reserves - Specific Reserve	478	572
Impaired loans with specific reserves - Average Recorded Investment	4,382	5,862
Impaired loans with no specific reserves - Recorded Investment	18,345	15,608
Impaired loans with no specific reserves - Unpaid Principal Balance	19,448	15,615
Impaired loans with no specific reserves - Interest Income Recognized	260	1,290
Impaired loans with no specific reserves - Average Recorded Investment	16,976	18,010
Impaired loans specific reserves - Recorded Investment	22,654	20,065
Impaired loans specific reserves - Unpaid Principal Balance	23,795	20,072
Impaired loans specific reserves - Interest Income Recognized	340	1,603
Impaired loans specific reserves - Average Recorded Investment	21,358	23,872
Loans
Carrying amount	1,007,370	986,684
Unamortized discounts on acquired loans	5,533	6,136
PCI loans
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserves - Specific Reserve	22,700
Loans
Carrying amount	5,134	5,373
Unamortized discounts on acquired loans	989
Individual evaluation for impairment not required	620
Real Estate Mortgage \| Construction and Land Development
Financing Receivable, Impaired [Line Items]
Impaired loans with no specific reserves - Recorded Investment	388	723
Impaired loans with no specific reserves - Unpaid Principal Balance	388	545
Impaired loans with no specific reserves - Interest Income Recognized	3	34
Impaired loans with no specific reserves - Average Recorded Investment	556	471
Real Estate Mortgage \| Residential Real Estate
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserves - Recorded Investment	691	727
Impaired loans with specific reserves - Unpaid Principal Balance	691	727
Impaired loans with specific reserves - Specific Reserve	181	216
Impaired loans with specific reserves - Average Recorded Investment	709	2,337
Impaired loans with no specific reserves - Recorded Investment	4,528	4,064
Impaired loans with no specific reserves - Unpaid Principal Balance	5,299	4,717
Impaired loans with no specific reserves - Interest Income Recognized	57	243
Impaired loans with no specific reserves - Average Recorded Investment	4,296	4,566
Real Estate Mortgage \| Nonresidential
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserves - Recorded Investment	2,411	2,456
Impaired loans with specific reserves - Unpaid Principal Balance	2,449	2,456
Impaired loans with specific reserves - Interest Income Recognized	69	260
Impaired loans with specific reserves - Specific Reserve	90	82
Impaired loans with specific reserves - Average Recorded Investment	2,433	2,866
Impaired loans with no specific reserves - Recorded Investment	12,365	9,734
Impaired loans with no specific reserves - Unpaid Principal Balance	12,697	9,266
Impaired loans with no specific reserves - Interest Income Recognized	182	909
Impaired loans with no specific reserves - Average Recorded Investment	11,050	11,181
Real Estate Mortgage \| Home Equity Loans
Financing Receivable, Impaired [Line Items]
Impaired loans with no specific reserves - Recorded Investment	56	9
Impaired loans with no specific reserves - Unpaid Principal Balance	56	9
Impaired loans with no specific reserves - Interest Income Recognized	1	17
Impaired loans with no specific reserves - Average Recorded Investment	32	351
Commercial
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserves - Recorded Investment	1,207	1,274
Impaired loans with specific reserves - Unpaid Principal Balance	1,207	1,274
Impaired loans with specific reserves - Interest Income Recognized	11	53
Impaired loans with specific reserves - Specific Reserve	207	274
Impaired loans with specific reserves - Average Recorded Investment	1,240	659
Impaired loans with no specific reserves - Recorded Investment	991	1,078
Impaired loans with no specific reserves - Unpaid Principal Balance	991	1,078
Impaired loans with no specific reserves - Interest Income Recognized	17	87
Impaired loans with no specific reserves - Average Recorded Investment	1,034	$ 1,441
Consumer and Other
Financing Receivable, Impaired [Line Items]
Impaired loans with no specific reserves - Recorded Investment	17
Impaired loans with no specific reserves - Unpaid Principal Balance	17
Impaired loans with no specific reserves - Average Recorded Investment	$ 8

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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