Loans and Allowance for Credit Losses - Allowance for Credit Losses Based on Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	$ 54,597	$ 38,381	$ 41,910	$ 26,911	$ 26,911
Initial allowance on loans purchased with credit deterioration			2,074
Provision for credit loss expense	1,103	3,883	12,679	15,500	16,103
Loans charged off	2,076	556	3,493	2,942	3,844
Recoveries collected	359	207	813	774	1,068
Allowance for credit losses, Ending Balance	53,983	41,915	53,983	41,915	41,910
Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				1,672	1,672
Construction and Land Development \| Real Estate Loan
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	1,795	2,358	1,666	1,146	1,146
Initial allowance on loans purchased with credit deterioration			261
Provision for credit loss expense	314	(139)	205	1,186	646
Loans charged off	0	13	23	13	13
Recoveries collected	0	0	0	0	0
Allowance for credit losses, Ending Balance	2,109	2,206	2,109	2,206	1,666
Construction and Land Development \| Real Estate Loan \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				(113)	(113)
Agricultural \| Real Estate Loan
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	1,665	1,634	1,084	1,093	1,093
Initial allowance on loans purchased with credit deterioration			44
Provision for credit loss expense	(408)	32	129	343	(239)
Loans charged off	0	0	0	0	0
Recoveries collected	0	0	0	0	0
Allowance for credit losses, Ending Balance	1,257	1,666	1,257	1,666	1,084
Agricultural \| Real Estate Loan \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				230	230
Residential Properties \| Real Estate Loan \| 1-4 Family
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	2,570	2,486	2,322	1,386	1,386
Initial allowance on loans purchased with credit deterioration			328
Provision for credit loss expense	27	(71)	117	335	274
Loans charged off	45	48	241	313	393
Recoveries collected	108	24	134	227	299
Allowance for credit losses, Ending Balance	2,660	2,391	2,660	2,391	2,322
Residential Properties \| Real Estate Loan \| 1-4 Family \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				756	756
Commercial \| Real Estate Loan
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	25,664	16,272	19,660	11,198	11,198
Initial allowance on loans purchased with credit deterioration			646
Provision for credit loss expense	(52)	2,463	5,764	7,542	8,581
Loans charged off	55	0	535	551	829
Recoveries collected	23	73	45	78	169
Allowance for credit losses, Ending Balance	25,580	18,808	25,580	18,808	19,660
Commercial \| Real Estate Loan \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				541	541
Agricultural Loans
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	906	1,323	1,526	1,386	1,386
Initial allowance on loans purchased with credit deterioration			0
Provision for credit loss expense	(90)	(89)	(711)	211	503
Loans charged off	0	0	0	0	0
Recoveries collected	0	0	1	0	0
Allowance for credit losses, Ending Balance	816	1,234	816	1,234	1,526
Agricultural Loans \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				(363)	(363)
Commercial and Industrial Loans
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	19,842	12,360	13,485	9,273	9,273
Initial allowance on loans purchased with credit deterioration			795
Provision for credit loss expense	342	1,352	5,950	5,453	5,869
Loans charged off	1,600	368	1,686	1,651	1,991
Recoveries collected	24	28	64	142	179
Allowance for credit losses, Ending Balance	18,608	13,372	18,608	13,372	13,485
Commercial and Industrial Loans \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				155	155
Consumer Loans
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance	2,155	1,948	2,167	1,429	1,429
Initial allowance on loans purchased with credit deterioration			0
Provision for credit loss expense	970	335	1,225	430	469
Loans charged off	376	127	1,008	414	618
Recoveries collected	204	82	569	327	421
Allowance for credit losses, Ending Balance	$ 2,953	$ 2,238	$ 2,953	2,238	2,167
Consumer Loans \| Cumulative Change in Accounting Principal, Adjustment \| ASU 2016-13
Allowance for loan losses [Abstract]
Allowance for credit losses, Beginning Balance				$ 466	$ 466

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Amount of increase in allowance for credit loss on financing receivable purchased with credit deterioration.

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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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