Loans and Allowance for Losses and Concentrations of Credit Risk - Impaired Financing Receivables (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Payments to Acquire Other Loans and Leases Held-for-investment	$ 300			$ 2,244		$ 440
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	24,751			24,751			$ 22,291
Impaired Financing Receivable, with Related Allowance, Recorded Investment	71,599	[1]		71,599	[1]		61,772	[2]
Impaired Financing Receivable, Recorded Investment	96,350			96,350			84,063
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	24,637			24,637			21,840
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	71,407			71,407			60,597
Impaired Financing Receivable, Unpaid Principal Balance	96,044			96,044			82,437
Impaired Financing Receivable, Related Allowance	5,686			5,686			2,637
Financing Receivable, Recorded Investment, Nonaccrual Status	29,315	[3]		29,315	[3]		30,152	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	101,067		$ 87,836	94,434		91,494
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	419		468	1,331		1,349
Crops [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,616			5,616			4,877
Impaired Financing Receivable, with Related Allowance, Recorded Investment	22,672	[1]		22,672	[1]		10,753	[2]
Impaired Financing Receivable, Recorded Investment	28,288			28,288			15,630
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,537			5,537			4,723
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	22,563			22,563			10,042
Impaired Financing Receivable, Unpaid Principal Balance	28,100			28,100			14,765
Impaired Financing Receivable, Related Allowance	582			582			397
Financing Receivable, Recorded Investment, Nonaccrual Status	3,541	[3]		3,541	[3]		5,168	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	27,133		19,975	23,176		21,873
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	33		90	373		365
Permanent Plantings [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	13,666			13,666			5,837
Impaired Financing Receivable, with Related Allowance, Recorded Investment	19,462	[1]		19,462	[1]		33,690	[2]
Impaired Financing Receivable, Recorded Investment	33,128			33,128			39,527
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	13,639			13,639			5,750
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	19,429			19,429			33,393
Impaired Financing Receivable, Unpaid Principal Balance	33,068			33,068			39,143
Impaired Financing Receivable, Related Allowance	472			472			1,515
Financing Receivable, Recorded Investment, Nonaccrual Status	15,397	[3]		15,397	[3]		14,413	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	37,911		43,280	39,337		44,144
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	234		142	459		412
Livestock [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,635			3,635			9,576
Impaired Financing Receivable, with Related Allowance, Recorded Investment	8,007	[1]		8,007	[1]		5,979	[2]
Impaired Financing Receivable, Recorded Investment	11,642			11,642			15,555
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,630			3,630			9,386
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,982			7,982			5,897
Impaired Financing Receivable, Unpaid Principal Balance	11,612			11,612			15,283
Impaired Financing Receivable, Related Allowance	768			768			361
Financing Receivable, Recorded Investment, Nonaccrual Status	4,361	[3]		4,361	[3]		4,438	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	12,534		12,305	13,923		13,040
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	76		149	273		284
Part-Time Farm [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,834			1,834			2,001
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,958	[1]		7,958	[1]		11,350	[2]
Impaired Financing Receivable, Recorded Investment	9,792			9,792			13,351
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,831			1,831			1,981
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,933			7,933			11,265
Impaired Financing Receivable, Unpaid Principal Balance	9,764			9,764			13,246
Impaired Financing Receivable, Related Allowance	264			264			364
Financing Receivable, Recorded Investment, Nonaccrual Status	6,016	[3]		6,016	[3]		6,133	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	9,989		12,276	11,248		12,407
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	76		87	226		288
Agriculture Storage and Processing [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0			0			0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	13,500	[1]		13,500	[1]		0	[2]
Impaired Financing Receivable, Recorded Investment	13,500			13,500			0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0			0			0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	13,500			13,500			0
Impaired Financing Receivable, Unpaid Principal Balance	13,500			13,500			0
Impaired Financing Receivable, Related Allowance	3,600			3,600			0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]		0	[3]		0	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	13,500		0	6,750		0
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	0		0	0		0
Other Commodity [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0			0			0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	[1]		0	[1]		0	[2]
Impaired Financing Receivable, Recorded Investment	0			0			0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0			0			0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0			0			0
Impaired Financing Receivable, Unpaid Principal Balance	0			0			0
Impaired Financing Receivable, Related Allowance	0			0			0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[3]		0	[3]		0	[4]
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	0		0	0		30
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	0		$ 0	0		$ 0
Collateral Dependent Not Individually Analyzed [Member]
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, Recorded Investment	64,600			64,600			54,400
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, Related Allowance	$ 1,200			$ 1,200			$ 1,200
Impaired Financing Receivable, Impairment analysis performed percent	67.00%			67.00%			65.00%
Less than 90 days past due [Member]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 11,300	[3]		$ 11,300	[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 $64.6 million (67 percent) of impaired loans as of September 30, 2015, 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 $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 $11.3 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.