Loans and Allowance for Losses and Concentrations of Credit Risk - Impaired Financing Receivables (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	$ 22,291		$ 24,951
Impaired Financing Receivable, with Related Allowance, Recorded Investment	61,772	[1]	72,116	[2]
Impaired Financing Receivable, Recorded Investment	84,063		97,067
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	21,840		24,733
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	60,597		70,308
Impaired Financing Receivable, Unpaid Principal Balance	82,437		95,041
Impaired Financing Receivable, Related Allowance	2,637		2,696
Financing Receivable, Recorded Investment, Nonaccrual Status	30,152	[3]	37,228	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	90,009		101,732
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	1,533		3,768
Crops [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,877		6,956
Impaired Financing Receivable, with Related Allowance, Recorded Investment	10,753	[1]	16,697	[2]
Impaired Financing Receivable, Recorded Investment	15,630		23,653
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,723		6,825
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	10,042		16,284
Impaired Financing Receivable, Unpaid Principal Balance	14,765		23,109
Impaired Financing Receivable, Related Allowance	397		406
Financing Receivable, Recorded Investment, Nonaccrual Status	5,168	[3]	10,812	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	20,625		28,387
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	373		793
Permanent Plantings [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,837		9,880
Impaired Financing Receivable, with Related Allowance, Recorded Investment	33,690	[1]	36,146	[2]
Impaired Financing Receivable, Recorded Investment	39,527		46,026
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,750		9,877
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	33,393		34,978
Impaired Financing Receivable, Unpaid Principal Balance	39,143		44,855
Impaired Financing Receivable, Related Allowance	1,515		1,702
Financing Receivable, Recorded Investment, Nonaccrual Status	14,413	[3]	15,237	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	43,221		42,838
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	474		2,254
Livestock [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	9,576		6,671
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,979	[1]	7,600	[2]
Impaired Financing Receivable, Recorded Investment	15,555		14,271
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,386		6,588
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,897		7,455
Impaired Financing Receivable, Unpaid Principal Balance	15,283		14,043
Impaired Financing Receivable, Related Allowance	361		193
Financing Receivable, Recorded Investment, Nonaccrual Status	4,438	[3]	5,344	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	13,543		16,117
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	327		277
Part-Time Farm [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,001		1,444
Impaired Financing Receivable, with Related Allowance, Recorded Investment	11,350	[1]	11,554	[2]
Impaired Financing Receivable, Recorded Investment	13,351		12,998
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,981		1,443
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	11,265		11,476
Impaired Financing Receivable, Unpaid Principal Balance	13,246		12,919
Impaired Financing Receivable, Related Allowance	364		392
Financing Receivable, Recorded Investment, Nonaccrual Status	6,133	[3]	5,835	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	12,596		13,042
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	359		444
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		867
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]	119	[2]
Impaired Financing Receivable, Recorded Investment	0		119
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		115
Impaired Financing Receivable, Unpaid Principal Balance	0		115
Impaired Financing Receivable, Related Allowance	0		3
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]	0	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	24		481
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	54,400		65,100
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, Related Allowance	1,200		1,300
Impaired Financing Receivable, Impairment analysis performed percent	65.00%	[1]	67.00%
Less than 90 days past due [Member]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 11,700	[3]	$ 9,600	[4]

[1] 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.

[2] Impairment analysis was performed in the aggregate in consideration of similar risk characteristics of the assets and historical statistics on $65.1 million (67 percent) of impaired loans as of December 31, 2013, which resulted in a specific reserve of $1.3 million.

[3] 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.

[4] Includes $9.6 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.