Loans Receivable and the Allowance for Credit Losses - Pre-ASC 326 Impaired Loan Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2019
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			$ 21,568
Impaired financing receivable, with related allowance, recorded investment			11,927
Recorded Investment			33,495
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			25,790
Impaired financing receivable, with related allowance, unpaid principal balance			13,121
Unpaid Principal Balance			38,911
Related Allowance			3,663
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	$ 11,493	$ 10,101
Impaired financing receivable, with related allowance, average recorded investment	9,290	8,749
Average Recorded Investment	20,783	18,850
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	89	32
Impaired financing receivable, with related allowance, interest income, accrual method	74	85
Interest Income Recognized	163	117
Agricultural
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			2,383
Impaired financing receivable, with related allowance, recorded investment			1,929
Recorded Investment			4,312
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			2,913
Impaired financing receivable, with related allowance, unpaid principal balance			1,930
Unpaid Principal Balance			4,843
Related Allowance			212
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	2,632	2,227
Impaired financing receivable, with related allowance, average recorded investment	2,363	2,279
Average Recorded Investment	4,995	4,506
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	47	12
Impaired financing receivable, with related allowance, interest income, accrual method	53	60
Interest Income Recognized	100	72
Commercial and industrial
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			7,391
Impaired financing receivable, with related allowance, recorded investment			4,851
Recorded Investment			12,242
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			10,875
Impaired financing receivable, with related allowance, unpaid principal balance			5,417
Unpaid Principal Balance			16,292
Related Allowance			2,198
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	4,347	4,610
Impaired financing receivable, with related allowance, average recorded investment	4,271	4,042
Average Recorded Investment	8,618	8,652
Commercial real estate
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			11,196
Impaired financing receivable, with related allowance, recorded investment			4,886
Recorded Investment			16,082
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			11,403
Impaired financing receivable, with related allowance, unpaid principal balance			5,512
Unpaid Principal Balance			16,915
Related Allowance			1,180
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	3,921	2,868
Impaired financing receivable, with related allowance, average recorded investment	2,130	1,988
Average Recorded Investment	6,051	4,856
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	42	20
Impaired financing receivable, with related allowance, interest income, accrual method	15	17
Interest Income Recognized	57	37
Commercial real estate | Construction & development
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			1,181
Impaired financing receivable, with related allowance, recorded investment			135
Recorded Investment			1,316
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			1,218
Impaired financing receivable, with related allowance, unpaid principal balance			135
Unpaid Principal Balance			1,353
Related Allowance			135
Commercial real estate | Farmland
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			4,306
Impaired financing receivable, with related allowance, recorded investment			1,109
Recorded Investment			5,415
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			4,331
Impaired financing receivable, with related allowance, unpaid principal balance			1,148
Unpaid Principal Balance			5,479
Related Allowance			347
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	3,001	2,011
Impaired financing receivable, with related allowance, average recorded investment	86	57
Average Recorded Investment	3,087	2,068
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	32
Impaired financing receivable, with related allowance, interest income, accrual method	5	5
Interest Income Recognized	37	5
Commercial real estate | Commercial real estate-other
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			5,709
Impaired financing receivable, with related allowance, recorded investment			3,642
Recorded Investment			9,351
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			5,854
Impaired financing receivable, with related allowance, unpaid principal balance			4,229
Unpaid Principal Balance			10,083
Related Allowance			698
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	920	857
Impaired financing receivable, with related allowance, average recorded investment	2,044	1,931
Average Recorded Investment	2,964	2,788
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	10	20
Impaired financing receivable, with related allowance, interest income, accrual method	10	12
Interest Income Recognized	20	32
Residential real estate
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			577
Impaired financing receivable, with related allowance, recorded investment			261
Recorded Investment			838
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			578
Impaired financing receivable, with related allowance, unpaid principal balance			262
Unpaid Principal Balance			840
Related Allowance			73
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	572	382
Impaired financing receivable, with related allowance, average recorded investment	526	440
Average Recorded Investment	1,098	822
Interest Income Recognized
Impaired financing receivable, with related allowance, interest income, accrual method	6	8
Interest Income Recognized	6	8
Residential real estate | One- to four- family first liens
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			577
Impaired financing receivable, with related allowance, recorded investment			261
Recorded Investment			838
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			578
Impaired financing receivable, with related allowance, unpaid principal balance			262
Unpaid Principal Balance			840
Related Allowance			73
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	497	332
Impaired financing receivable, with related allowance, average recorded investment	526	440
Average Recorded Investment	1,023	772
Interest Income Recognized
Impaired financing receivable, with related allowance, interest income, accrual method	6	8
Interest Income Recognized	6	8
Residential real estate | One- to four- family junior liens
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	75	50
Average Recorded Investment	75	50
Consumer
Recorded Investment
Impaired financing receivable, with no related allowance, recorded investment			21
Recorded Investment			21
Unpaid Principal Balance
Impaired financing receivable, with no related allowance, unpaid principal balance			21
Unpaid Principal Balance			$ 21
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	21	14
Average Recorded Investment	$ 21	$ 14