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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loan and Lease Losses, Real Estate	$ 7,368		$ 7,368			$ 11,351
Reserve for losses	6,110		6,110			5,539
Financing Receivable, Allowance for Credit Losses	13,478	18,140	13,478	18,140	14,252	16,890	17,966	17,516
Provision for Loan Losses Expensed	(529)	(1,220)	(99)	(800)
Provision for losses	(175)	1,394	571	1,424
Total provision for/(release of) losses	(704)	174	472	624
Financing Receivable, Allowance for Credit Losses, Write-downs	(70)	0	(3,884)	0
Eligible Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Loan and Lease Losses, Real Estate	7,368	9,361	7,368	9,361	7,967	11,351	10,581	10,161
Provision for Loan Losses Expensed	(529)	(1,220)	(99)	(800)
Allowance for Loan and Lease Losses, Write-offs	(70)	0	(3,884)	0
Long-Term Standby Purchase Commitments and Farmer Mac Guaranteed Securities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reserve for losses	6,110	8,779	6,110	8,779	6,285	5,539	7,385	7,355
Provision for losses	(175)	1,394	571	1,424
Other Credit Losses, Write-Offs	0	0	0	0
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses	7,196	9,302	7,196	9,302	6,971	9,661	8,100	8,106
Total provision for/(release of) losses	225	1,202	1,160	1,196
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	(3,625)	0
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses	2,405	4,281	2,405	4,281	2,617	2,589	4,266	4,133
Total provision for/(release of) losses	(212)	15	(184)	148
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses	2,168	2,688	2,168	2,688	2,326	2,316	3,482	3,365
Total provision for/(release of) losses	(158)	(794)	41	(677)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	(189)	0
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses	1,279	463	1,279	463	1,587	1,534	636	685
Total provision for/(release of) losses	(308)	(173)	(255)	(222)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0	0	0
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses	425	1,399	425	1,399	733	784	1,475	1,223
Total provision for/(release of) losses	(238)	(76)	(289)	176
Financing Receivable, Allowance for Credit Losses, Write-downs	(70)	0	(70)	0
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses	5	7	5	7	18	6	7	4
Total provision for/(release of) losses	(13)	0	(1)	3
Financing Receivable, Allowance for Credit Losses, Write-downs	$ 0	$ 0	$ 0	$ 0