Loans - Summary of Troubled Debt Restructurings on Accruing and Nonaccrual Financing Receivables (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) contract	Dec. 31, 2019 USD ($) contract	Mar. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($) contract	Sep. 30, 2019 USD ($)
Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 41,382				$ 44,842
Financing receivable, modifications, number of contracts | contract	6	8	0	1
Financing receivable, modifications, pre-modification recorded investment	$ 7,874	$ 9,018	$ 0	$ 89
Financing receivable, modifications, post-modification recorded investment	$ 7,874	$ 9,018	$ 0	$ 89
Change in recorded investment due to principal paydown at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to principal paydown at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to chargeoffs at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, post-modification recorded investment	0	$ 0	$ 0	$ 0
Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 28,042				30,073
Financing receivable, modifications, number of contracts | contract	0	13	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 4,501	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	$ 0	$ 4,501	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to principal paydown at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to chargeoffs at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, post-modification recorded investment	0	$ 0	$ 0	$ 0
Commercial real estate | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 19,843				17,145
Financing receivable, modifications, number of contracts | contract	1	1	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 2,879	$ 2,879	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	2,879	$ 2,879	$ 0	$ 0
Commercial real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 3,088				904
Financing receivable, modifications, number of contracts | contract	0	1	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 2,216	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 2,216	$ 0	$ 0
Agriculture | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 11,838				22,929
Financing receivable, modifications, number of contracts | contract	2	2	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 993	$ 993	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	993	$ 993	$ 0	$ 0
Agriculture | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 20,357				24,762
Financing receivable, modifications, number of contracts | contract	0	10	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 1,455	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 1,455	$ 0	$ 0
Commercial non-real estate | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 9,402				4,398
Financing receivable, modifications, number of contracts | contract	2	4	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 3,952	$ 5,096	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	3,952	$ 5,096	$ 0	$ 0
Commercial non-real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 4,465				4,257
Financing receivable, modifications, number of contracts | contract	0	2	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 830	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 830	$ 0	$ 0
Residential real estate | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 294				263
Financing receivable, modifications, number of contracts | contract	1	1	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 50	$ 50	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	50	$ 50	$ 0	$ 0
Residential real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 92				102
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	$ 0	$ 0
Consumer | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 5				107
Financing receivable, modifications, number of contracts | contract	0	0	0	1
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 89
Financing receivable, modifications, post-modification recorded investment	0	$ 0	$ 0	$ 89
Consumer | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 40				$ 48
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	$ 0	$ 0	$ 0	$ 0