Loans and Allowance for Loan Losses - Loans by Credit Quality Indicator and Origination Year (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 836,158
2019	897,538
2018	438,147
2017	428,510
2016	225,466
Prior	706,385
Revolving Loans Amortized Cost Basis	257,771
Total	3,789,975	$ 3,568,204
Construction Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	87,515
2019	215,612
2018	108,910
2017	74,431
2016	3,576
Prior	9,492
Revolving Loans Amortized Cost Basis	110,858
Total	610,394	644,948
Construction Real Estate Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	87,515
2019	214,617
2018	108,910
2017	74,431
2016	3,553
Prior	9,241
Revolving Loans Amortized Cost Basis	110,858
Total	609,125
Construction Real Estate Loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	23
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	23
Construction Real Estate Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Construction Real Estate Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	995
2018	0
2017	0
2016	0
Prior	63
Revolving Loans Amortized Cost Basis	0
Total	1,058
Construction Real Estate Loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	188
Revolving Loans Amortized Cost Basis	0
Total	188
1-4 Family Residential Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	113,367
2019	124,089
2018	79,149
2017	63,284
2016	67,450
Prior	287,755
Revolving Loans Amortized Cost Basis	3,249
Total	738,343	787,562
1-4 Family Residential Real Estate Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	113,367
2019	124,089
2018	79,065
2017	62,838
2016	65,842
Prior	282,651
Revolving Loans Amortized Cost Basis	3,135
Total	730,987
1-4 Family Residential Real Estate Loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	14
Revolving Loans Amortized Cost Basis	0
Total	14
1-4 Family Residential Real Estate Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	12
Revolving Loans Amortized Cost Basis	0
Total	12
1-4 Family Residential Real Estate Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	84
2017	286
2016	1,461
Prior	4,599
Revolving Loans Amortized Cost Basis	114
Total	6,544
1-4 Family Residential Real Estate Loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	160
2016	147
Prior	479
Revolving Loans Amortized Cost Basis	0
Total	786
Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	184,064
2019	382,735
2018	173,167
2017	210,424
2016	120,766
Prior	249,435
Revolving Loans Amortized Cost Basis	6,642
Total	1,327,233	1,250,208
Commercial Real Estate Loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	168,851
2019	347,128
2018	161,643
2017	210,171
2016	115,591
Prior	226,048
Revolving Loans Amortized Cost Basis	6,642
Total	1,236,074
Commercial Real Estate Loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	2,211
2017	0
2016	0
Prior	2,587
Revolving Loans Amortized Cost Basis	0
Total	4,798
Commercial Real Estate Loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,983
2019	33,008
2018	7,067
2017	141
2016	4,543
Prior	7,846
Revolving Loans Amortized Cost Basis	0
Total	58,588
Commercial Real Estate Loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	9,230
2019	2,599
2018	2,246
2017	112
2016	632
Prior	12,898
Revolving Loans Amortized Cost Basis	0
Total	27,717
Commercial Real Estate Loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	56
Revolving Loans Amortized Cost Basis	0
Total	56
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	367,108
2019	74,690
2018	28,947
2017	11,738
2016	5,318
Prior	8,255
Revolving Loans Amortized Cost Basis	133,114
Total	629,170	401,521
Commercial loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	366,405
2019	72,148
2018	27,755
2017	11,448
2016	4,989
Prior	7,484
Revolving Loans Amortized Cost Basis	127,918
Total	618,147
Commercial loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	324
2019	835
2018	31
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	204
Total	1,394
Commercial loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	693
2018	450
2017	208
2016	325
Prior	606
Revolving Loans Amortized Cost Basis	391
Total	2,673
Commercial loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	379
2019	906
2018	203
2017	20
2016	1
Prior	165
Revolving Loans Amortized Cost Basis	4,601
Total	6,275
Commercial loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	108
2018	508
2017	62
2016	3
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	681
Municipal loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	43,539
2019	69,964
2018	35,013
2017	62,626
2016	25,873
Prior	150,271
Revolving Loans Amortized Cost Basis	0
Total	387,286	383,960
Municipal loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	43,539
2019	69,964
2018	35,013
2017	62,626
2016	25,873
Prior	150,271
Revolving Loans Amortized Cost Basis	0
Total	387,286
Municipal loans | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Municipal loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Municipal loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Municipal loans | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Loans to individuals
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40,565
2019	30,448
2018	12,961
2017	6,007
2016	2,483
Prior	1,177
Revolving Loans Amortized Cost Basis	3,908
Total	97,549	$ 100,005
Loans to individuals | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40,522
2019	30,412
2018	12,870
2017	5,910
2016	2,370
Prior	1,158
Revolving Loans Amortized Cost Basis	3,897
Total	97,139
Loans to individuals | Pass Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Loans to individuals | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	53
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	4
Total	57
Loans to individuals | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3
2019	32
2018	31
2017	64
2016	22
Prior	14
Revolving Loans Amortized Cost Basis	7
Total	173
Loans to individuals | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2020	40
2019	4
2018	7
2017	33
2016	91
Prior	5
Revolving Loans Amortized Cost Basis	0
Total	$ 180