Loans - Changes in the Allowance for Losses (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Provision for/(release of) losses	$ 56,000	$ 913,000
Agricultural Finance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	3,442,000	3,745,000	$ 3,745,000
Provision for/(release of) losses	590,000	(27,000)
Charge-offs	(84,000)	0	0
Ending balance	3,948,000	3,718,000	3,442,000
Agricultural Finance | Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Provision for/(release of) losses	0	0
Rural Infrastructure Finance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	10,599,000	10,087,000	10,087,000
Provision for/(release of) losses	(977,000)	1,002,000
Charge-offs	0	0	0
Ending balance	9,622,000	11,089,000	$ 10,599,000
Rural Infrastructure Finance | Collateral Pledged
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Provision for/(release of) losses	$ 0	$ 0