Loans and Allowance for Losses and Concentrations of Credit Risk - Allowance for Credit Losses Roll Forward (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Allowance for Loan Losses			$ 6,866
Beginning Balance - Reserve for Losses			6,468
Beginning Balance - Total Allowance for Losses	11,365	13,478	13,334	16,890
Provision for Loan Losses Expensed	511	(499)	(499)	(598)
(Release of)/provision for reserve for losses	(1,315)	463	(2,188)	1,034
Provision For (Reduction Of) Loan Lease And Other Losses	(804)	(36)	(2,687)	436
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	86	3,884
Financing Receivable, Allowance for Credit Losses, Recovery	45	0	45	0
Ending Balance - Allowance for Loan Losses	6,326		6,326
Ending Balance - Reserve for Losses	4,280		4,280
Ending Balance - Total Allowance for Losses	10,606	13,442	10,606	13,442
Eligible Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Allowance for Loan Losses	5,770	7,368	6,866	11,351
Provision for Loan Losses Expensed	511	(499)	(499)	(598)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	86	3,884
Financing Receivable, Allowance for Credit Losses, Recovery	45	0	45	0
Ending Balance - Allowance for Loan Losses	6,326	6,869	6,326	6,869
Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Reserve for Losses	5,595	6,110	6,468	5,539
(Release of)/provision for reserve for losses	(1,315)	463	(2,188)	1,034
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	0	0	0	0
Ending Balance - Reserve for Losses	4,280	6,573	4,280	6,573
Crops [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	2,390	2,405	2,124	2,589
Provision For (Reduction Of) Loan Lease And Other Losses	123	(225)	389	(409)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	0		0
Ending Balance - Total Allowance for Losses	2,513	2,180	2,513	2,180
Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	4,999	7,196	7,292	9,661
Provision For (Reduction Of) Loan Lease And Other Losses	(992)	364	(3,285)	1,524
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	3,625
Financing Receivable, Allowance for Credit Losses, Recovery	0		0
Ending Balance - Total Allowance for Losses	4,007	7,560	4,007	7,560
Agriculture Storage and Processing [Member] | Eligible Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Losses, Write-downs				3,600
Other Commodity [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	4	5	7	6
Provision For (Reduction Of) Loan Lease And Other Losses	0	1	(3)	0
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Financing Receivable, Allowance for Credit Losses, Recovery	0		0
Ending Balance - Total Allowance for Losses	4	6	4	6
Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	2,217	2,168	2,186	2,316
Provision For (Reduction Of) Loan Lease And Other Losses	74	(105)	105	(64)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	189
Financing Receivable, Allowance for Credit Losses, Recovery	45		45
Ending Balance - Total Allowance for Losses	2,336	2,063	2,336	2,063
Livestock [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	1,311	1,279	1,271	1,534
Provision For (Reduction Of) Loan Lease And Other Losses	(6)	(84)	91	(339)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	57	0
Financing Receivable, Allowance for Credit Losses, Recovery	0		0
Ending Balance - Total Allowance for Losses	1,305	1,195	1,305	1,195
Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	444	425	454	784
Provision For (Reduction Of) Loan Lease And Other Losses	(3)	13	16	(276)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	29	70
Financing Receivable, Allowance for Credit Losses, Recovery	0		0
Ending Balance - Total Allowance for Losses	$ 441	$ 438	$ 441	$ 438