Loans - Changes in the Allowance for Losses (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Release of)/provision for losses	$ (860,000)	$ 7,805,000	$ 3,504,000
Charge-offs		(5,800,000)
Agricultural Finance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	3,745,000	10,454,000	7,017,000
(Release of)/provision for losses	(1,357,000)	2,959,000	3,504,000
Recovery	1,054,000	0
Charge-offs	0	(5,759,000)	(67,000)
Ending balance	3,442,000	3,745,000	10,454,000
Agricultural Finance | Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Release of)/provision for losses	0	0
Agricultural Finance | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		(3,909,000)
Ending balance			(3,909,000)
Agricultural Finance | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		6,545,000
Ending balance			6,545,000
Rural Infrastructure Finance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	10,087,000	0	0
(Release of)/provision for losses	512,000	4,709,000	0
Recovery	0	0
Charge-offs	0	0	0
Ending balance	10,599,000	10,087,000	0
Rural Infrastructure Finance | Collateral Pledged
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Release of)/provision for losses	$ 0	0
Rural Infrastructure Finance | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		5,378,000
Ending balance			5,378,000
Rural Infrastructure Finance | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		$ 5,378,000
Ending balance			$ 5,378,000