Loans and Allowance for Losses and Concentrations of Credit Risk - Financing Receivables Credit Quality Indicators (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	$ 5,417,174	[1],[2]	$ 5,163,080	[1],[2]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	18,917	[1]	28,296	[3]
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	5,172,691	[1]	4,845,302	[1]
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	111,888	[1],[4]	122,830	[1],[4]
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	132,595	[1],[5]	194,948	[1],[5]
On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	2,540,222	[1]	2,135,467	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	18,427	[1]	27,580	[3]
On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	2,419,285	[1]	1,988,945	[1]
On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	54,495	[1],[4]	47,171	[1],[4]
On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	66,442	[1],[5]	99,351	[1],[5]
Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	2,876,952	[1]	3,027,613	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	490	[1]	716	[3]
Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	2,753,406	[1]	2,856,357	[1]
Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	57,393	[1],[4]	75,659	[1],[4]
Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	66,153	[1],[5]	95,597	[1],[5]
Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	2,941,266	[1]	2,666,857	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	4,175	[1]	8,256	[3]
Crops [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	2,887,319	[1]	2,600,039	[1]
Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	30,417	[1],[4]	26,633	[1],[4]
Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	23,530	[1],[5]	40,185	[1],[5]
Crops [Member] | On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,633,667	[1]	1,385,008	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	4,175	[1]	8,036	[3]
Crops [Member] | On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,604,546	[1]	1,348,205	[1]
Crops [Member] | On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	16,814	[1],[4]	15,656	[1],[4]
Crops [Member] | On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	12,307	[1],[5]	21,147	[1],[5]
Crops [Member] | Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,307,599	[1]	1,281,849	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	220	[3]
Crops [Member] | Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,282,773	[1]	1,251,834	[1]
Crops [Member] | Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	13,603	[1],[4]	10,977	[1],[4]
Crops [Member] | Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	11,223	[1],[5]	19,038	[1],[5]
Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	920,195	[1]	907,824	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	6,869	[1]	11,841	[3]
Permanent Plantings [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	856,901	[1]	838,318	[1]
Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	18,180	[1],[4]	20,594	[1],[4]
Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	45,114	[1],[5]	48,912	[1],[5]
Permanent Plantings [Member] | On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	395,421	[1]	336,478	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	6,869	[1]	11,841	[3]
Permanent Plantings [Member] | On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	353,487	[1]	290,064	[1]
Permanent Plantings [Member] | On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	6,030	[1],[4]	4,973	[1],[4]
Permanent Plantings [Member] | On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	35,904	[1],[5]	41,441	[1],[5]
Permanent Plantings [Member] | Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	524,774	[1]	571,346	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	0	[3]
Permanent Plantings [Member] | Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	503,414	[1]	548,254	[1]
Permanent Plantings [Member] | Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	12,150	[1],[4]	15,621	[1],[4]
Permanent Plantings [Member] | Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	9,210	[1],[5]	7,471	[1],[5]
Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,260,618	[1]	1,246,105	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	5,045	[1]	4,462	[3]
Livestock [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,174,057	[1]	1,144,438	[1]
Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	61,320	[1],[4]	55,912	[1],[4]
Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	25,241	[1],[5]	45,755	[1],[5]
Livestock [Member] | On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	412,620	[1]	330,509	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	4,555	[1]	4,462	[3]
Livestock [Member] | On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	375,010	[1]	300,308	[1]
Livestock [Member] | On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	31,039	[1],[4]	19,357	[1],[4]
Livestock [Member] | On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	6,571	[1],[5]	10,844	[1],[5]
Livestock [Member] | Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	847,998	[1]	915,596	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	490	[1]	0	[3]
Livestock [Member] | Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	799,047	[1]	844,130	[1]
Livestock [Member] | Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	30,281	[1],[4]	36,555	[1],[4]
Livestock [Member] | Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	18,670	[1],[5]	34,911	[1],[5]
Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	173,954	[1]	162,743	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	2,828	[1]	3,618	[3]
Part-Time Farm [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	154,931	[1]	144,611	[1]
Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,963	[1],[4]	1,835	[1],[4]
Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	17,060	[1],[5]	16,297	[1],[5]
Part-Time Farm [Member] | On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	69,511	[1]	50,362	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	2,828	[1]	3,122	[3]
Part-Time Farm [Member] | On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	57,239	[1]	39,022	[1]
Part-Time Farm [Member] | On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	612	[1],[4]	918	[1],[4]
Part-Time Farm [Member] | On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	11,660	[1],[5]	10,422	[1],[5]
Part-Time Farm [Member] | Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	104,443	[1]	112,381	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	496	[3]
Part-Time Farm [Member] | Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	97,692	[1]	105,589	[1]
Part-Time Farm [Member] | Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	1,351	[1],[4]	917	[1],[4]
Part-Time Farm [Member] | Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	5,400	[1],[5]	5,875	[1],[5]
Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	114,360	[1]	170,918	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	0	[3]
Agriculture Storage and Processing [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	93,366	[1]	110,059	[1]
Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1],[4]	17,278	[1],[4]
Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	20,994	[1],[5]	43,581	[1],[5]
Agriculture Storage and Processing [Member] | On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	29,003	[1]	32,636	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	0	[3]
Agriculture Storage and Processing [Member] | On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	29,003	[1]	10,987	[1]
Agriculture Storage and Processing [Member] | On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1],[4]	6,267	[1],[4]
Agriculture Storage and Processing [Member] | On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1],[5]	15,382	[1],[5]
Agriculture Storage and Processing [Member] | Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	85,357	[1]	138,282	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	0	[3]
Agriculture Storage and Processing [Member] | Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	64,363	[1]	99,072	[1]
Agriculture Storage and Processing [Member] | Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1],[4]	11,011	[1],[4]
Agriculture Storage and Processing [Member] | Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	20,994	[1],[5]	28,199	[1],[5]
Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	6,781	[1]	8,633	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	119	[3]
Other Commodity [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	6,117	[1]	7,837	[1]
Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	8	[1],[4]	578	[1],[4]
Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	656	[1],[5]	218	[1],[5]
Other Commodity [Member] | On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1]	474	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	119	[3]
Other Commodity [Member] | On-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1]	359	[1]
Other Commodity [Member] | On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1],[4]	0	[1],[4]
Other Commodity [Member] | On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	0	[1],[5]	115	[1],[5]
Other Commodity [Member] | Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	6,781	[1]	8,159	[1]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	[1]	0	[3]
Other Commodity [Member] | Off-balance sheet [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	6,117	[1]	7,478	[1]
Other Commodity [Member] | Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	8	[1],[4]	578	[1],[4]
Other Commodity [Member] | Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	$ 656	[1],[5]	$ 103	[1],[5]

[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).

[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.

[4] Assets in the Special mention category generally have potential weaknesses due to performance issues but are currently considered to be adequately secured.

[5] Substandard assets have a well-defined weakness or weaknesses and there is a distinct possibility that some loss will be sustained if deficiencies are not corrected.