Allowance for Losses and Concentration of Credit Risk - Allowance for losses activity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		12 Months Ended	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Eligible Loans [Member]	Jun. 30, 2011 Eligible Loans [Member]	Jun. 30, 2012 Eligible Loans [Member]	Jun. 30, 2011 Eligible Loans [Member]	Jun. 30, 2012 Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities	Jun. 30, 2011 Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities	Jun. 30, 2012 Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities	Jun. 30, 2011 Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities	Jun. 30, 2012 Crops	Jun. 30, 2011 Crops	Jun. 30, 2012 Crops	Jun. 30, 2011 Crops	Jun. 30, 2012 Permanent Plantings	Jun. 30, 2011 Permanent Plantings	Jun. 30, 2012 Permanent Plantings	Jun. 30, 2011 Permanent Plantings	Jun. 30, 2012 Livestock	Jun. 30, 2011 Livestock	Jun. 30, 2012 Livestock	Jun. 30, 2011 Livestock	Jun. 30, 2012 Part-Time Farm	Jun. 30, 2011 Part-Time Farm	Jun. 30, 2012 Part-Time Farm	Jun. 30, 2011 Part-Time Farm	Jun. 30, 2012 Ag Storage and Processing (including ethanol facilities)	Jun. 30, 2011 Ag Storage and Processing (including ethanol facilities)	Jun. 30, 2012 Ag Storage and Processing (including ethanol facilities)	Jun. 30, 2011 Ag Storage and Processing (including ethanol facilities)	Jun. 30, 2012 Other	Jun. 30, 2011 Other	Jun. 30, 2012 Other	Jun. 30, 2011 Other	Jun. 30, 2012 Specific Reserve new appraisal or payment [Member] Eligible Loans [Member]	Jun. 30, 2012 Specific reserve reclassification [Member] Eligible Loans [Member]	Dec. 31, 2010 Specific reserve reclassification [Member] LTSPCs	Jun. 30, 2012 Specific Reverve change total [Member] Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance, Allowance for Loan Losses			$ 10,161		$ 10,581	$ 11,084	$ 10,161	$ 9,803
Beginning Balance, Reserve for Losses			7,355						7,385	8,378	7,355	10,312
Beginning Balance, Total Allowance	17,966	19,462	17,516	20,115									4,266	3,922	4,133	3,572	3,482	3,802	3,365	3,537	636	1,850	685	2,749	1,475	1,053	1,223	445	8,100	8,823	8,106	9,797	7	12	4	15
(Relase of)/provision for losses, Allowance for Loan Losses	(1,220)	160	(800)	1,441	(1,220)	160	(800)	1,441
(Release of)/provision for losses, Reserve for Losses	1,394	(935)	1,424	(2,869)					1,394	(935)	1,424	(2,869)
(Release of)/provision for losses, Total Allowance	174	(775)	624	(1,428)									15	(31)	148	319	(794)	8	(677)	273	(173)	(68)	(222)	(967)	(76)	42	176	650	1,202	(723)	1,196	(1,697)	0	(3)	3	(6)	900	(300)	1,800	1,200
Charge-offs, Allowance for Losses					0	(191)	0	(191)
Charge-offs, Reserve for Losses									0	0	0	0
Charge-offs, Total Allowance	0	(191)	0	(191)									0	(176)	0	(176)	0	(7)	0	(7)	0	(8)	0	(8)	0	0	0	0	0	0	0	0	0	0	0	0
Ending Balance, Allowance for Loan Losses	9,361		9,361		9,361	11,053	9,361	11,053
Ending Balance, Reserve for Losses	8,779		8,779						8,779	7,443	8,779	7,443
Ending Balance, Total Allowance	$ 18,140	$ 18,496	$ 18,140	$ 18,496									$ 4,281	$ 3,715	$ 4,281	$ 3,715	$ 2,688	$ 3,803	$ 2,688	$ 3,803	$ 463	$ 1,774	$ 463	$ 1,774	$ 1,399	$ 1,095	$ 1,399	$ 1,095	$ 9,302	$ 8,100	$ 9,302	$ 8,100	$ 7	$ 9	$ 7	$ 9