Loans and Allowance for Loan Losses - Allowance for Credit Losses Based on Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	$ 32,876	$ 26,704	$ 26,911	$ 26,189	$ 26,189
Provision for credit loss expense	6,136	91	11,617	1,038	6,433
Loans charged off	963	542	2,386	1,110	6,326
Recoveries collected	332	106	567	242	615
Ending balance	38,381	26,359	38,381	26,359	26,911
Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			1,672
Construction and Land Development \| Real Estate Loan
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	1,620	552	1,146	561	561
Provision for credit loss expense	738	187	1,325	178	585
Loans charged off	0	0	0	0	0
Recoveries collected	0	0	0	0	0
Ending balance	2,358	739	2,358	739	1,146
Construction and Land Development \| Real Estate Loan \| Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			(113)
Agricultural \| Real Estate Loan
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	1,335	1,282	1,093	1,246	1,246
Provision for credit loss expense	299	2	311	38	(153)
Loans charged off	0	0	0	0	0
Recoveries collected	0	0	0	0	0
Ending balance	1,634	1,284	1,634	1,284	1,093
Agricultural \| Real Estate Loan \| Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			230
Residential Properties \| Real Estate Loan \| 1-4 Family
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	1,931	1,341	1,386	1,504	1,504
Provision for credit loss expense	483	367	406	326	1,268
Loans charged off	69	66	265	197	1,478
Recoveries collected	141	7	203	16	92
Ending balance	2,486	1,649	2,486	1,649	1,386
Residential Properties \| Real Estate Loan \| Accounting Standards Update 2016-13 \| 1-4 Family
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			756
Commercial \| Real Estate Loan
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	13,621	10,565	11,198	11,102	11,102
Provision for credit loss expense	3,118	335	5,079	(146)	1,827
Loans charged off	467	105	551	161	1,743
Recoveries collected	0	1	5	1	12
Ending balance	16,272	10,796	16,272	10,796	11,198
Commercial \| Real Estate Loan \| Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			541
Agricultural Loans
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	1,064	1,130	1,386	951	951
Provision for credit loss expense	259	542	300	730	459
Loans charged off	0	0	0	9	24
Recoveries collected	0	0	0	0	0
Ending balance	1,323	1,672	1,323	1,672	1,386
Agricultural Loans \| Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			(363)
Commercial And Industrial Portfolio Segment
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	11,294	10,830	9,273	9,893	9,893
Provision for credit loss expense	1,286	(1,558)	4,101	(546)	1,053
Loans charged off	311	155	1,283	258	1,828
Recoveries collected	91	12	114	40	155
Ending balance	12,360	9,129	12,360	9,129	9,273
Commercial And Industrial Portfolio Segment \| Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			155
Consumer Loans
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	2,011	1,004	1,429	932	932
Provision for credit loss expense	(47)	216	95	458	1,394
Loans charged off	116	216	287	485	1,253
Recoveries collected	100	86	245	185	356
Ending balance	$ 1,948	$ 1,090	1,948	$ 1,090	$ 1,429
Consumer Loans \| Accounting Standards Update 2016-13
Allowance for loan losses [Abstract]
Impact of adopting ASU 2016-13			$ 466

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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