Loans and Allowance for Losses and Concentrations of Credit Risk - Impaired Financing Receivables (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 91,931		$ 105,707	$ 102,898		$ 100,787
Impaired Financing Receivable, Recorded Investment	88,578			88,578			100,351
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	28,066			28,066			30,638
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	27,828			27,828			30,236
Impaired Financing Receivable, with Related Allowance, Recorded Investment	60,512	[1]		60,512	[1]		69,713	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	57,315			57,315			68,601
Impaired Financing Receivable, Unpaid Principal Balance	85,143			85,143			98,837
Impaired Financing Receivable, Related Allowance	2,566			2,566			6,659
Financing Receivable, Recorded Investment, Nonaccrual Status	38,264	[3]		38,264	[3]		45,335	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	542		1,257	1,906		2,364
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	27,311		31,490	29,570		29,583
Impaired Financing Receivable, Recorded Investment	24,015			24,015			24,509
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,636			5,636			7,295
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,554			5,554			7,247
Impaired Financing Receivable, with Related Allowance, Recorded Investment	18,379	[1]		18,379	[1]		17,214	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	17,450			17,450			16,829
Impaired Financing Receivable, Unpaid Principal Balance	23,004			23,004			24,076
Impaired Financing Receivable, Related Allowance	481			481			706
Financing Receivable, Recorded Investment, Nonaccrual Status	10,647	[3]		10,647	[3]		11,888	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	248		72	651		213
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	37,340		34,566	42,041		34,284
Impaired Financing Receivable, Recorded Investment	37,346			37,346			38,219
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	13,590			13,590			11,652
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	13,528			13,528			11,509
Impaired Financing Receivable, with Related Allowance, Recorded Investment	23,756	[1]		23,756	[1]		26,567	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	21,723			21,723			26,095
Impaired Financing Receivable, Unpaid Principal Balance	35,251			35,251			37,604
Impaired Financing Receivable, Related Allowance	1,530			1,530			1,515
Financing Receivable, Recorded Investment, Nonaccrual Status	16,158	[3]		16,158	[3]		15,789	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	169		1,015	666		1,691
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	15,252		17,643	16,579		14,973
Impaired Financing Receivable, Recorded Investment	14,506			14,506			17,004
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	7,175			7,175			7,644
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	7,094			7,094			7,489
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,331	[1]		7,331	[1]		9,360	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,188			7,188			9,219
Impaired Financing Receivable, Unpaid Principal Balance	14,282			14,282			16,708
Impaired Financing Receivable, Related Allowance	184			184			355
Financing Receivable, Recorded Investment, Nonaccrual Status	5,473	[3]		5,473	[3]		5,141	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	38		94	230		210
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	11,909		16,526	13,053		16,127
Impaired Financing Receivable, Recorded Investment	12,592			12,592			15,258
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,665			1,665			3,140
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,652			1,652			3,090
Impaired Financing Receivable, with Related Allowance, Recorded Investment	10,927	[1]		10,927	[1]		12,118	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	10,839			10,839			12,007
Impaired Financing Receivable, Unpaid Principal Balance	12,491			12,491			15,097
Impaired Financing Receivable, Related Allowance	369			369			682
Financing Receivable, Recorded Investment, Nonaccrual Status	5,986	[3]		5,986	[3]		8,180	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	87		76	359		250
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	0		4,449	1,084		4,785
Impaired Financing Receivable, Recorded Investment	0			0			4,337
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0			0			0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0			0			0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	[1]		0	[1]		4,337	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0			0			4,337
Impaired Financing Receivable, Unpaid Principal Balance	0			0			4,337
Impaired Financing Receivable, Related Allowance	0			0			3,400
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]		0	[3]		4,337	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	0		0	0		0
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	119		1,033	571		1,035
Impaired Financing Receivable, Recorded Investment	119			119			1,024
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0			0			907
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0			0			901
Impaired Financing Receivable, with Related Allowance, Recorded Investment	119	[1]		119	[1]		117	[2]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	115			115			114
Impaired Financing Receivable, Unpaid Principal Balance	115			115			1,015
Impaired Financing Receivable, Related Allowance	2			2			1
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]		0	[3]		0	[4]
Impaired Financing Receivable, Interest Income, Accrual Method	0		0	0		0
Less than 90 days past due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	5,600	[3]		5,600	[3]		15,700	[4]
Collateral Dependent Not Individually Analyzed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Recorded Investment	53,600			53,600			56,000	[2]
Impaired Financing Receivable, Impairment analysis performed percent	61.00%	[1]		61.00%	[1]		56.00%	[2]
Impaired Financing Receivable, Related Allowance	$ 1,300	[1]		$ 1,300	[1]		$ 1,100

[1] Impairment analysis was performed in the aggregate in consideration of similar risk characteristics of the assets and historical statistics on $53.6 million (61 percent) of impaired loans as of September 30, 2013, which resulted in a specific reserve of $1.3 million.

[2] Impairment analysis was performed in the aggregate in consideration of similar risk characteristics of the assets and historical statistics on $56.0 million (56 percent) of impaired loans as of December 31, 2012, which resulted in a specific reserve of $1.1 million.

[3] Includes $5.6 million of loans that are less than 90 days delinquent but which have not met Farmer Mac's performance criteria for returning to accrual status.

[4] Includes $15.7 million of loans that are less than 90 days delinquent but which have not met Farmer Mac's performance criteria for returning to accrual status.