Farmer Mac Guaranteed Securities and USDA Guaranteed Securities (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended
Jun. 30, 2012	Dec. 31, 2011
Payment Guarantee [Member] \| Farmer Mac and USDA Guaranteed Securities
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale Securities, Amortized Cost	$ 5,716,690	$ 5,431,203
Available-for-sale Securities, Unrealized Gains	148,687	139,214
Available-for-sale Securities, Unrealized Losses	(2,272)	(1,599)
Total available-for-sale	5,863,105	5,568,818
Marketable Securities, Amortized Cost	5,866,435	5,644,333
Marketable Securities, Unrealized Gains	149,603	141,018
Marketable Securities, Unrealized Losses	(6,108)	(4,174)
Marketable securities	6,009,930	5,781,177
Farmer Mac Guarantee \| Farmer Mac I Guaranteed Securities
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale Securities, Amortized Cost	3,140,176	2,741,192
Available-for-sale Securities, Unrealized Gains	85,220	67,895
Available-for-sale Securities, Unrealized Losses	(2,064)	(1,460)
Total available-for-sale	3,223,332	2,807,627
Farmer Mac Guarantee \| Farmer Mac II Guaranteed Securities
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale Securities, Amortized Cost	28,677	34,692
Available-for-sale Securities, Unrealized Gains	1,231	924
Available-for-sale Securities, Unrealized Losses	(9)	(17)
Total available-for-sale	29,899	35,599
Farmer Mac Guarantee \| Farmer Mac Guaranteed Securities - Rural Utilities
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale Securities, Amortized Cost	1,165,100	1,410,800
Available-for-sale Securities, Unrealized Gains	26,136	35,246
Available-for-sale Securities, Unrealized Losses	0	0
Total available-for-sale	1,191,236	1,446,046
USDA Guarantee \| USDA Guaranteed Securities
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale Securities, Amortized Cost	1,382,737	1,244,519
Available-for-sale Securities, Unrealized Gains	36,100	35,149
Available-for-sale Securities, Unrealized Losses	(199)	(122)
Total available-for-sale	1,418,638	1,279,546
Trading Securities Amortized Cost	149,745	213,130
Trading Securities, Unrealized Gains	916	1,804
Trading Securities, Unrealized Losses	(3,836)	(2,575)
Trading securities	$ 146,825	$ 212,359

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