Loans Receivable and the Allowance for Credit Losses - Pre-ASC 326 Impaired Loan Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 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	$ 6,457
Impaired financing receivable, with related allowance, average recorded investment	14,008
Average Recorded Investment	20,465
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	7
Impaired financing receivable, with related allowance, interest income, accrual method	4
Interest Income Recognized	11
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	1,538
Impaired financing receivable, with related allowance, average recorded investment	2,735
Average Recorded Investment	4,273
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	2,343
Impaired financing receivable, with related allowance, average recorded investment	5,460
Average Recorded Investment	7,803
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	2,196
Impaired financing receivable, with related allowance, average recorded investment	5,408
Average Recorded Investment	7,604
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	6
Impaired financing receivable, with related allowance, interest income, accrual method	3
Interest Income Recognized	9
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	1,011
Impaired financing receivable, with related allowance, average recorded investment	1,442
Average Recorded Investment	2,453
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	1,185
Impaired financing receivable, with related allowance, average recorded investment	3,966
Average Recorded Investment	5,151
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	6
Impaired financing receivable, with related allowance, interest income, accrual method	3
Interest Income Recognized	9
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	380
Impaired financing receivable, with related allowance, average recorded investment	394
Average Recorded Investment	774
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	1
Impaired financing receivable, with related allowance, interest income, accrual method	1
Interest Income Recognized	2
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	75
Impaired financing receivable, with related allowance, average recorded investment	394
Average Recorded Investment	469
Interest Income Recognized
Impaired financing receivable, with related allowance, interest income, accrual method	1
Interest Income Recognized	1
Residential real estate | One- to four- family junior liens
Average Recorded Investment
Impaired financing receivable, with no related allowance, average recorded investment	305
Average Recorded Investment	305
Interest Income Recognized
Impaired financing receivable, with no related allowance, interest income, accrual method	1
Interest Income Recognized	1
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 related allowance, average recorded investment	11
Average Recorded Investment	$ 11