Loans Receivable and the Allowance for Credit Losses - Nonaccrual Status and Interest Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	$ 41,303	$ 41,303	$ 41,483
Nonaccrual with no Allowance for Credit Losses	23,329	23,329
90 Days or More Past Due And Accruing	3,238	3,238	136
Interest Income Recognized on Nonaccrual	124	396
Agricultural
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	3,187	3,187	2,894
Nonaccrual with no Allowance for Credit Losses	1,611	1,611
90 Days or More Past Due And Accruing	0	0	0
Interest Income Recognized on Nonaccrual	16	80
Commercial and industrial
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	10,041	10,041	13,276
Nonaccrual with no Allowance for Credit Losses	5,104	5,104
90 Days or More Past Due And Accruing	35	35	0
Interest Income Recognized on Nonaccrual	45	101
Commercial real estate
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	25,037	25,037	22,037
Nonaccrual with no Allowance for Credit Losses	16,393	16,393
90 Days or More Past Due And Accruing	0	0	0
Interest Income Recognized on Nonaccrual	18	159
Commercial real estate \| Construction & development
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	879	879	1,494
Nonaccrual with no Allowance for Credit Losses	701	701
90 Days or More Past Due And Accruing	0	0	0
Interest Income Recognized on Nonaccrual	6	41
Commercial real estate \| Farmland
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	14,178	14,178	10,402
Nonaccrual with no Allowance for Credit Losses	12,593	12,593
90 Days or More Past Due And Accruing	0	0	0
Interest Income Recognized on Nonaccrual	9	93
Commercial real estate \| Multifamily
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	0	0	0
Nonaccrual with no Allowance for Credit Losses	0	0
90 Days or More Past Due And Accruing	0	0	0
Interest Income Recognized on Nonaccrual	0	1
Commercial real estate \| Commercial real estate-other
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	9,980	9,980	10,141
Nonaccrual with no Allowance for Credit Losses	3,099	3,099
90 Days or More Past Due And Accruing	0	0	0
Interest Income Recognized on Nonaccrual	3	24
Residential real estate
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	2,876	2,876	3,070
Nonaccrual with no Allowance for Credit Losses	208	208
90 Days or More Past Due And Accruing	3,197	3,197	124
Interest Income Recognized on Nonaccrual	39	48
Residential real estate \| One- to four- family first liens
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	2,293	2,293	2,557
Nonaccrual with no Allowance for Credit Losses	207	207
90 Days or More Past Due And Accruing	3,197	3,197	99
Interest Income Recognized on Nonaccrual	33	41
Residential real estate \| One- to four- family junior liens
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	583	583	513
Nonaccrual with no Allowance for Credit Losses	1	1
90 Days or More Past Due And Accruing	0	0	25
Interest Income Recognized on Nonaccrual	6	7
Consumer
Financing Receivable, Recorded Investment, Past Due
Nonaccrual	162	162	206
Nonaccrual with no Allowance for Credit Losses	13	13
90 Days or More Past Due And Accruing	6	6	$ 12
Interest Income Recognized on Nonaccrual	$ 6	$ 8

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