Loans and Allowance for Loan Losses - Aging of Past Due Loans by Class of Loan (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Loans	$ 3,647,585	$ 3,657,779
Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	3,642,611	3,636,192
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	3,372	10,440
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	979	7,437
Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	623	3,710
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	4,974	21,587
Construction Real Estate Loans
Financing Receivable, Past Due [Line Items]
Loans	422,095	581,941
Construction Real Estate Loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	421,982	581,388
Construction Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	72	95
Construction Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	41	14
Construction Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	444
Construction Real Estate Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	113	553
1-4 Family Residential Real Estate Loans
Financing Receivable, Past Due [Line Items]
Loans	660,689	719,952
1-4 Family Residential Real Estate Loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	658,766	706,781
1-4 Family Residential Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	652	7,872
1-4 Family Residential Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	691	2,469
1-4 Family Residential Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	580	2,830
1-4 Family Residential Real Estate Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,923	13,171
Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Loans	1,605,132	1,295,746
Commercial Real Estate Loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	1,604,247	1,294,878
Commercial Real Estate Loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	885	467
Commercial Real Estate Loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	315
Commercial Real Estate Loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	86
Commercial Real Estate Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	885	868
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans	443,708	557,122
Commercial loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	442,042	550,860
Commercial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,402	1,423
Commercial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	233	4,516
Commercial loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	31	323
Commercial loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,666	6,262
Municipal loans
Financing Receivable, Past Due [Line Items]
Loans	427,259	409,028
Municipal loans | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	427,163	408,964
Municipal loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	96	64
Municipal loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Municipal loans | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Municipal loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	96	64
Loans to individuals
Financing Receivable, Past Due [Line Items]
Loans	88,702	93,990
Loans to individuals | Financial Asset, Current
Financing Receivable, Past Due [Line Items]
Loans	88,411	93,321
Loans to individuals | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	265	519
Loans to individuals | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	14	123
Loans to individuals | Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	12	27
Loans to individuals | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans	$ 291	$ 669