Fair Value Disclosures - Summary of Carrying Value and Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Assets	$ (24,759)	$ (29,523)
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	893,387	785,564
Loans	2,832,842	2,746,742
Derivative Assets	26,254	31,173
Notes payable - Due within one year	6,552,954	6,573,013
Notes payable - Due after one year	5,128,379	5,202,751
Debt securities of consolidated trusts held by third parties	173,575	164,910
Financial derivatives, Liabilities	133,838	150,682
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	893,387	785,564
Loans	2,765,926	2,729,774
Derivative Assets	26,254	31,173
Notes payable - Due within one year	6,543,973	6,567,366
Notes payable - Due after one year	4,978,118	5,034,739
Debt securities of consolidated trusts held by third parties	167,250	167,621
Financial derivatives, Liabilities	133,838	150,682
Investment Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	2,297,316	2,499,629
Investment Securities [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	2,297,316	2,499,629
Farmer Mac Guaranteed Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable	18,844	20,432
Farmer Mac Guaranteed Securities [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable	17,706	18,926
Long-Term Standby Purchase Commitments [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable	29,225	27,805
Long-Term Standby Purchase Commitments [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable	24,653	22,863
Long-Term Standby Purchase Commitments [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment obligations	28,317	26,896
Long-Term Standby Purchase Commitments [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment obligations	23,745	21,954
Farmer Mac Guaranteed Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment obligations	16,297	17,354
Farmer Mac Guaranteed Securities [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment obligations	15,160	15,849
Farmer Mac Guarantee | Farmer Mac Guaranteed Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	5,100,080	4,766,258
Farmer Mac Guarantee | Farmer Mac Guaranteed Securities [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	5,100,080	4,766,258
USDA Guarantee | USDA Guaranteed Securities [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	1,656,431	1,590,783
USDA Guarantee | USDA Guaranteed Securities [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	$ 1,656,431	$ 1,590,783