Allowance for Losses and Concentration of Credit Risk - Credit Quality Indicator (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	$ 4,403,212	[1]	$ 4,349,163	[1]
90 days or more past due	47,026	[2]	40,623	[1]
Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	4,031,004	[1]	3,942,725	[1]
Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	187,370	[1],[3]	208,894	[1],[3]
Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	184,838	[1],[3]	197,544	[1],[3]
Crops
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	1,941,075	[1]	1,864,959	[1]
90 days or more past due	14,274	[2]	11,605	[1]
Crops | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	1,860,579	[1]	1,769,768	[1]
Crops | Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	40,386	[1],[3]	60,076	[1],[3]
Crops | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	40,110	[1],[3]	35,115	[1],[3]
Permanent Plantings
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	823,399	[1]	824,345	[1]
90 days or more past due	15,223	[2]	19,228	[1]
Permanent Plantings | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	744,379	[1]	748,558	[1]
Permanent Plantings | Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	27,071	[1],[3]	20,442	[1],[3]
Permanent Plantings | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	51,949	[1],[3]	55,345	[1],[3]
Livestock
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	1,218,721	[1]	1,224,111	[1]
90 days or more past due	10,251	[2]	2,475	[1]
Livestock | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	1,104,200	[1]	1,097,184	[1]
Livestock | Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	65,297	[1],[3]	74,959	[1],[3]
Livestock | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	49,224	[1],[3]	51,968	[1],[3]
Part-Time Farm
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	224,465	[1]	245,120	[1]
90 days or more past due	7,278	[2]	7,315	[1]
Part-Time Farm | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	198,092	[1]	215,525	[1]
Part-Time Farm | Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	6,590	[1],[3]	7,103	[1],[3]
Part-Time Farm | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	19,783	[1],[3]	22,492	[1],[3]
Ag Storage and Processing (including ethanol facilities)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	181,355	[1]	173,692	[1]
90 days or more past due	0	[2]	0	[1]
Ag Storage and Processing (including ethanol facilities) | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	111,317	[1]	96,532	[1]
Ag Storage and Processing (including ethanol facilities) | Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	47,393	[1],[3]	45,673	[1],[3]
Ag Storage and Processing (including ethanol facilities) | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	22,645	[1],[3]	31,487	[1],[3]
Other
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	14,197	[1]	16,936	[1]
90 days or more past due	0	[2]	0	[1]
Other | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	12,437	[1]	15,158	[1]
Other | Other Assets Especially Mentioned (OAEM)
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	633	[1],[3]	641	[1],[3]
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing receivable, loans	$ 1,127	[1],[3]	$ 1,137	[1],[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] Includes loans and loans underlying Farmer Mac I Guaranteed Securities and LTSPCs that are 90 days or more past due, in foreclosure, restructured after delinquency, and in bankruptcy, excluding loans performing under either their original loan terms or a court-approved bankruptcy plan.

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