Loans and Allowance for Losses and Concentrations of Credit Risk - Allowance for Losses by Impairment Method and Commodity (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	$ 5,228,505			$ 5,068,039
Financing Receivable, Individually Evaluated for Impairment	85,932			95,041
Financing Receivable, Gross	5,314,437	[1],[2]		5,163,080	[1],[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	7,747			10,638
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	2,859			2,696
Financing Receivable, Allowance for Credit Losses	10,606		11,365	13,334		13,442	13,478	16,890
Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	2,862,700			2,643,748
Financing Receivable, Individually Evaluated for Impairment	17,545			23,109
Financing Receivable, Gross	2,880,245	[2]		2,666,857	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	2,087			1,718
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	426			406
Financing Receivable, Allowance for Credit Losses	2,513		2,390	2,124		2,180	2,405	2,589
Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	861,492			862,969
Financing Receivable, Individually Evaluated for Impairment	43,589			44,855
Financing Receivable, Gross	905,081	[2]		907,824	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	555			484
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	1,781			1,702
Financing Receivable, Allowance for Credit Losses	2,336		2,217	2,186		2,063	2,168	2,316
Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	1,235,052			1,232,062
Financing Receivable, Individually Evaluated for Impairment	12,338			14,043
Financing Receivable, Gross	1,247,390	[2]		1,246,105	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,014			1,078
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	291			193
Financing Receivable, Allowance for Credit Losses	1,305		1,311	1,271		1,195	1,279	1,534
Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	140,455			149,824
Financing Receivable, Individually Evaluated for Impairment	12,460			12,919
Financing Receivable, Gross	152,915	[2]		162,743	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	80			62
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	361			392
Financing Receivable, Allowance for Credit Losses	441		444	454		438	425	784
Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	120,876			170,918
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	120,876	[2]		170,918	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,007			7,292
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Financing Receivable, Allowance for Credit Losses	4,007		4,999	7,292		7,560	7,196	9,661
Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	7,930			8,518
Financing Receivable, Individually Evaluated for Impairment	0			115
Financing Receivable, Gross	7,930	[2]		8,633	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4			4
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			3
Financing Receivable, Allowance for Credit Losses	4		4	7		6	5	6
On-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	2,307,912			2,051,498
Financing Receivable, Individually Evaluated for Impairment	72,536			83,969
Financing Receivable, Gross	2,380,448	[2]		2,135,467	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,668			4,392
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	2,658			2,474
Financing Receivable, Allowance for Credit Losses	6,326			6,866
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	1,528,563			1,363,861
Financing Receivable, Individually Evaluated for Impairment	14,243			21,147
Financing Receivable, Gross	1,542,806	[2]		1,385,008	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,811			1,321
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	339			362
Financing Receivable, Allowance for Credit Losses	2,150			1,683
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	333,512			295,037
Financing Receivable, Individually Evaluated for Impairment	40,315			41,441
Financing Receivable, Gross	373,827	[2]		336,478	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	408			325
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	1,744			1,641
Financing Receivable, Allowance for Credit Losses	2,152			1,966
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	376,526			319,665
Financing Receivable, Individually Evaluated for Impairment	7,236			10,844
Financing Receivable, Gross	383,762	[2]		330,509	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	541			436
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	267			140
Financing Receivable, Allowance for Credit Losses	808			576
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	39,079			39,940
Financing Receivable, Individually Evaluated for Impairment	10,742			10,422
Financing Receivable, Gross	49,821	[2]		50,362	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	29			20
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	308			331
Financing Receivable, Allowance for Credit Losses	337			351
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	29,635			32,636
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	29,635	[2]		32,636	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	879			2,290
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Financing Receivable, Allowance for Credit Losses	879			2,290
On-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	597			359
Financing Receivable, Individually Evaluated for Impairment	0			115
Financing Receivable, Gross	597	[2]		474	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	0			0
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Financing Receivable, Allowance for Credit Losses	0			0
Off-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	2,920,593			3,016,541
Financing Receivable, Individually Evaluated for Impairment	13,396			11,072
Financing Receivable, Gross	2,933,989	[2]		3,027,613	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,079			6,246
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	201			222
Financing Receivable, Allowance for Credit Losses	4,280			6,468
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	1,334,137			1,279,887
Financing Receivable, Individually Evaluated for Impairment	3,302			1,962
Financing Receivable, Gross	1,337,439	[2]		1,281,849	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	276			397
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	87			44
Financing Receivable, Allowance for Credit Losses	363			441
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	527,980			567,932
Financing Receivable, Individually Evaluated for Impairment	3,274			3,414
Financing Receivable, Gross	531,254	[2]		571,346	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	147			159
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	37			61
Financing Receivable, Allowance for Credit Losses	184			220
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	858,526			912,397
Financing Receivable, Individually Evaluated for Impairment	5,102			3,199
Financing Receivable, Gross	863,628	[2]		915,596	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	473			642
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	24			53
Financing Receivable, Allowance for Credit Losses	497			695
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	101,376			109,884
Financing Receivable, Individually Evaluated for Impairment	1,718			2,497
Financing Receivable, Gross	103,094	[2]		112,381	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	51			42
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	53			61
Financing Receivable, Allowance for Credit Losses	104			103
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	91,241			138,282
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	91,241	[2]		138,282	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,128			5,002
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Financing Receivable, Allowance for Credit Losses	3,128			5,002
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment	7,333			8,159
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	7,333	[2]		8,159	[2]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4			4
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			3
Financing Receivable, Allowance for Credit Losses	$ 4			$ 7

[1] Geographic regions: Northwest (AK, ID, MT, OR, WA, WY); Southwest (AZ, CA, CO, HI, NM, NV, UT); Mid-North (IA, IL, IN, MI, MN, NE, ND, SD, WI); Mid-South (AR, KS, LA, MO, OK, TX); Northeast (CT, DE, KY, MA, MD, ME, NH, NJ, NY, OH, PA, RI, VA, VT, WV); Southeast (AL, FL, GA, MS, NC, SC, TN).

[2] Amounts represent unpaid principal balance of risk-rated loans, which is the basis Farmer Mac uses to analyze its portfolio, and recorded investment of past due loans.