Loans and Allowance for Loan Losses - Aging of Past Due Loans by Class of Loan (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 15,071	$ 21,587
Current	3,701,527	3,636,192
Total loans	3,716,598	3,657,779
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	13,052	10,440
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	889	7,437
Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,130	3,710
Construction Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	1,130	553
Current	604,547	581,388
Total loans	605,677	581,941
Construction Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,130	95
Construction Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	14
Construction Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	444
1-4 Family Residential Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	6,421	13,171
Current	694,009	706,781
Total loans	700,430	719,952
1-4 Family Residential Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,321	7,872
1-4 Family Residential Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	614	2,469
1-4 Family Residential Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	486	2,830
Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	4,676	868
Current	1,343,875	1,294,878
Total loans	1,348,551	1,295,746
Commercial Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4,676	467
Commercial Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	315
Commercial Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	86
Commercial loans
Financing Receivable, Past Due [Line Items]
Total Past Due	2,393	6,262
Current	562,352	550,860
Total loans	564,745	557,122
Commercial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,507	1,423
Commercial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	245	4,516
Commercial loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	641	323
Municipal loans
Financing Receivable, Past Due [Line Items]
Total Past Due	0	64
Current	406,377	408,964
Total loans	406,377	409,028
Municipal loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	64
Municipal loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Municipal loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Loans to individuals
Financing Receivable, Past Due [Line Items]
Total Past Due	451	669
Current	90,367	93,321
Total loans	90,818	93,990
Loans to individuals | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	418	519
Loans to individuals | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	30	123
Loans to individuals | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 3	$ 27