Loans and Allowance for Losses and Concentrations of Credit Risk - Allowance for Losses by Impairment Method and Commodity (Details) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		$ 5,637,597	$ 5,649,604
Financing Receivable, Individually Evaluated for Impairment		76,192	75,695
Financing Receivable, Gross	[1],[2]	5,713,789	5,725,299
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		4,591	4,713
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		2,035	1,850
Financing Receivable, Allowance for Credit Losses		6,626	6,563	$ 9,431	$ 10,127
Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		3,229,810	3,224,911
Financing Receivable, Individually Evaluated for Impairment		27,327	18,740
Financing Receivable, Gross	[1]	3,257,137	3,243,651
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		2,248	2,315
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		644	476
Financing Receivable, Allowance for Credit Losses		2,892	2,791	2,640	2,519
Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		913,423	917,127
Financing Receivable, Individually Evaluated for Impairment		22,867	24,284
Financing Receivable, Gross	[1]	936,290	941,411
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		626	571
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		311	360
Financing Receivable, Allowance for Credit Losses		937	931	2,284	2,159
Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		1,195,938	1,221,983
Financing Receivable, Individually Evaluated for Impairment		17,243	14,798
Financing Receivable, Gross	[1]	1,213,181	1,236,781
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		923	994
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		840	787
Financing Receivable, Allowance for Credit Losses		1,763	1,781	1,343	1,423
Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		229,717	203,090
Financing Receivable, Individually Evaluated for Impairment		8,755	8,035
Financing Receivable, Gross	[1]	238,472	211,125
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		204	181
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		240	227
Financing Receivable, Allowance for Credit Losses		444	408	459	467
Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		59,870	72,152
Financing Receivable, Individually Evaluated for Impairment		0	9,838
Financing Receivable, Gross	[1]	59,870	81,990
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		587	649
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		0	0
Financing Receivable, Allowance for Credit Losses		587	649	2,698	3,552
Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		8,839	10,341
Financing Receivable, Individually Evaluated for Impairment		0	0
Financing Receivable, Gross	[1]	8,839	10,341
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		3	3
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		0	0
Financing Receivable, Allowance for Credit Losses		3	3	$ 7	$ 7
On-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		2,965,172	2,900,868
Financing Receivable, Individually Evaluated for Impairment		57,286	57,107
Financing Receivable, Gross	[1]	3,022,458	2,957,975
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		3,239	3,387
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		1,290	1,093
Financing Receivable, Allowance for Credit Losses		4,529	4,480
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		1,938,160	1,911,039
Financing Receivable, Individually Evaluated for Impairment		21,078	12,803
Financing Receivable, Gross	[1]	1,959,238	1,923,842
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,930	1,968
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		449	290
Financing Receivable, Allowance for Credit Losses		2,379	2,258
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		441,233	433,654
Financing Receivable, Individually Evaluated for Impairment		19,896	21,247
Financing Receivable, Gross	[1]	461,129	454,901
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		450	434
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		216	218
Financing Receivable, Allowance for Credit Losses		666	652
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		450,524	444,320
Financing Receivable, Individually Evaluated for Impairment		8,700	5,958
Financing Receivable, Gross	[1]	459,224	450,278
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		654	702
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		421	384
Financing Receivable, Allowance for Credit Losses		1,075	1,086
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		116,093	92,712
Financing Receivable, Individually Evaluated for Impairment		7,612	7,261
Financing Receivable, Gross	[1]	123,705	99,973
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		144	116
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		204	201
Financing Receivable, Allowance for Credit Losses		348	317
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		15,501	15,944
Financing Receivable, Individually Evaluated for Impairment		0	9,838
Financing Receivable, Gross	[1]	15,501	25,782
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		61	167
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		0	0
Financing Receivable, Allowance for Credit Losses		61	167
On-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		3,661	3,199
Financing Receivable, Individually Evaluated for Impairment		0	0
Financing Receivable, Gross	[1]	3,661	3,199
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		2,672,425	2,748,736
Financing Receivable, Individually Evaluated for Impairment		18,906	18,588
Financing Receivable, Gross	[1]	2,691,331	2,767,324
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		1,352	1,326
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		745	757
Financing Receivable, Allowance for Credit Losses		2,097	2,083
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		1,291,650	1,313,872
Financing Receivable, Individually Evaluated for Impairment		6,249	5,937
Financing Receivable, Gross	[1]	1,297,899	1,319,809
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		318	347
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		195	186
Financing Receivable, Allowance for Credit Losses		513	533
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		472,190	483,473
Financing Receivable, Individually Evaluated for Impairment		2,971	3,037
Financing Receivable, Gross	[1]	475,161	486,510
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		176	137
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		95	142
Financing Receivable, Allowance for Credit Losses		271	279
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		745,414	777,663
Financing Receivable, Individually Evaluated for Impairment		8,543	8,840
Financing Receivable, Gross	[1]	753,957	786,503
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		269	292
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		419	403
Financing Receivable, Allowance for Credit Losses		688	695
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		113,624	110,378
Financing Receivable, Individually Evaluated for Impairment		1,143	774
Financing Receivable, Gross	[1]	114,767	111,152
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		60	65
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		36	26
Financing Receivable, Allowance for Credit Losses		96	91
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		44,369	56,208
Financing Receivable, Individually Evaluated for Impairment		0	0
Financing Receivable, Gross	[1]	44,369	56,208
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		526	482
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		0	0
Financing Receivable, Allowance for Credit Losses		526	482
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Financing Receivable, Collectively Evaluated for Impairment		5,178	7,142
Financing Receivable, Individually Evaluated for Impairment		0	0
Financing Receivable, Gross	[1]	5,178	7,142
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment		3	3
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment		0	0
Financing Receivable, Allowance for Credit Losses		$ 3	$ 3

[1] 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.

[2] 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).