Loans and Allowance for Losses and Concentrations of Credit Risk - Impaired Financing Receivables (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 19,724			$ 22,291
Impaired Financing Receivable, with Related Allowance, Recorded Investment	71,812	[1]		61,772	[2]
Impaired Financing Receivable, Recorded Investment	91,536			84,063
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	19,316			21,840
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	69,419			60,597
Impaired Financing Receivable, Unpaid Principal Balance	88,735			82,437
Impaired Financing Receivable, Related Allowance	2,955			2,637
Financing Receivable, Recorded Investment, Nonaccrual Status	38,483	[3]		30,152	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	87,800		95,154
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	571		562
Crops [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,117			4,877
Impaired Financing Receivable, with Related Allowance, Recorded Investment	19,689	[1]		10,753	[2]
Impaired Financing Receivable, Recorded Investment	22,806			15,630
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,982			4,723
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	18,182			10,042
Impaired Financing Receivable, Unpaid Principal Balance	21,164			14,765
Impaired Financing Receivable, Related Allowance	640			397
Financing Receivable, Recorded Investment, Nonaccrual Status	3,588	[3]		5,168	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	19,218		23,772
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	282		170
Permanent Plantings [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,622			5,837
Impaired Financing Receivable, with Related Allowance, Recorded Investment	36,378	[1]		33,690	[2]
Impaired Financing Receivable, Recorded Investment	42,000			39,527
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,535			5,750
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	35,669			33,393
Impaired Financing Receivable, Unpaid Principal Balance	41,204			39,143
Impaired Financing Receivable, Related Allowance	1,609			1,515
Financing Receivable, Recorded Investment, Nonaccrual Status	24,582	[3]		14,413	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	40,764		45,008
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	83		194
Livestock [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	9,360			9,576
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,707	[1]		5,979	[2]
Impaired Financing Receivable, Recorded Investment	15,067			15,555
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,174			9,386
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,615			5,897
Impaired Financing Receivable, Unpaid Principal Balance	14,789			15,283
Impaired Financing Receivable, Related Allowance	349			361
Financing Receivable, Recorded Investment, Nonaccrual Status	4,180	[3]		4,438	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	15,311		13,776
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	148		76
Part-Time Farm [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,625			2,001
Impaired Financing Receivable, with Related Allowance, Recorded Investment	10,038	[1]		11,350	[2]
Impaired Financing Receivable, Recorded Investment	11,663			13,351
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,625			1,981
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	9,953			11,265
Impaired Financing Receivable, Unpaid Principal Balance	11,578			13,246
Impaired Financing Receivable, Related Allowance	357			364
Financing Receivable, Recorded Investment, Nonaccrual Status	6,133	[3]		6,133	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	12,507		12,538
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	58		122
Agriculture Storage and Processing [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0			0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	[1]		0	[2]
Impaired Financing Receivable, Recorded Investment	0			0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0			0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0			0
Impaired Financing Receivable, Unpaid Principal Balance	0			0
Impaired Financing Receivable, Related Allowance	0			0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]		0	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	0		0
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	0		0
Other Commodity [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0			0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	[1]		0	[2]
Impaired Financing Receivable, Recorded Investment	0			0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0			0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0			0
Impaired Financing Receivable, Unpaid Principal Balance	0			0
Impaired Financing Receivable, Related Allowance	0			0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]		0	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	0		60
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	0		0
Collateral Dependent Not Individually Analyzed [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, Recorded Investment	64,100			54,400
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, Related Allowance	1,600			(1,200)
Impaired Financing Receivable, Impairment analysis performed percent	70.00%			65.00%
Less than 90 days past due [Member]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 8,300	[3]		$ 11,700	[4]

[1] Impairment analysis was performed in the aggregate in consideration of similar risk characteristics of the assets and historical statistics on $64.1 million (70 percent) of impaired loans as of March 31, 2015, which resulted in a specific reserve of $1.6 million.

[2] Impairment analysis was performed in the aggregate in consideration of similar risk characteristics of the assets and historical statistics on $54.4 million (65 percent) of impaired loans as of December 31, 2014, which resulted in a specific reserve of $1.2 million.

[3] Includes $8.3 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 $11.7 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.