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Loans - Allowance for Losses Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 10,454	$ 13,832	$ 10,454
Increase (Decrease) in allowance for loan losses	3,504	7,805	3,504	$ 238
Current period charge-offs		(5,800)
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans					$ 2,656
Farm & Ranch
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	10,454	3,745	10,454	7,017		$ 6,796
Increase (Decrease) in allowance for loan losses		2,959	3,504	238
Current period charge-offs		(5,759)
Farm & Ranch \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	(3,909)		(3,909)		(3,909)
Rural Utilities:
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	0	10,087	0	0		$ 0
Increase (Decrease) in allowance for loan losses		4,709	0	0
Current period charge-offs		$ 0
Rural Utilities: \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 5,378		5,378		$ 5,378
Farm & Ranch and Rural Utilities
Financing Receivable, Allowance for Credit Losses [Line Items]
Increase (Decrease) in allowance for loan losses			$ (3,200)	$ (1,400)