Accounting Policies - Principles of Consolidation (Details) (USD $)	3 Months Ended
	Mar. 31, 2015 subsidiary		Dec. 31, 2014
Variable Interest Entity [Line Items]
Number of Subsidiaries	3
Loans held for investment in consolidated trusts, at amortized cost	$ 457,117,000		$ 692,478,000
Debt securities of consolidated trusts held by third parties	457,903,000		424,214,000
Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Other Liabilities	800,000		2,900,000
USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	400,000		(200,000)
Rural Utilities [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Unamortized Premium			3,700,000
Institutional Credit [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	2,400,000		2,400,000
On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	457,117,000	[1]	692,478,000	[2]
Debt securities of consolidated trusts held by third parties	457,903,000	[3]	424,214,000	[4]
On-balance sheet [Member] | Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	457,117,000	[1]	421,355,000	[2]
Debt securities of consolidated trusts held by third parties	457,903,000	[3]	424,214,000	[4]
On-balance sheet [Member] | USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	[1]	0	[2]
Debt securities of consolidated trusts held by third parties	0	[3]	0	[4]
On-balance sheet [Member] | Rural Utilities [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	[1]	271,123,000	[2]
Debt securities of consolidated trusts held by third parties	0	[3]	0	[4]
On-balance sheet [Member] | Institutional Credit [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	[1]	0	[2]
Debt securities of consolidated trusts held by third parties	0	[3]	0	[4]
On-balance sheet [Member] | Corporate [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	[1]	0	[2]
Debt securities of consolidated trusts held by third parties	0	[3]	0	[4]
Off-balance sheet [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,581,083,000	[5]	1,620,064,000	[6],[7]
Off-balance sheet [Member] | Farm & Ranch [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	598,236,000	[5]	636,086,000	[6],[7]
Off-balance sheet [Member] | USDA Guarantees [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	12,847,000	[5]	13,978,000	[6],[7]
Off-balance sheet [Member] | Rural Utilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[6],[7]
Off-balance sheet [Member] | Institutional Credit [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	970,000,000	[5]	970,000,000	[6],[7]
Off-balance sheet [Member] | Corporate [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[6],[7]
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	55,872,000	[8]	60,035,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	53,098,000	[5]	57,832,000	[7]
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Farm & Ranch [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[8]	0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[7]
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | USDA Guarantees [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	23,505,000	[8]	27,620,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	23,098,000	[5]	27,832,000	[7]
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Rural Utilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[8]	0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[7]
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Institutional Credit [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	32,367,000	[8]	32,415,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000,000	[5]	30,000,000	[7]
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Corporate [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[8]	0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[7]
Investment Securities [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	6,966,000		7,471,000
Investment Securities [Member] | On-balance sheet [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	479,548,000	[6]	409,657,000	[5]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	482,757,000	[5],[6]	412,690,000	[5],[7]
Investment Securities [Member] | On-balance sheet [Member] | Farm & Ranch [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[6]	0	[5]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[6]	0	[5],[7]
Investment Securities [Member] | On-balance sheet [Member] | USDA Guarantees [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[6]	0	[5]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[6]	0	[5],[7]
Investment Securities [Member] | On-balance sheet [Member] | Rural Utilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[6]	0	[5]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[6]	0	[5],[7]
Investment Securities [Member] | On-balance sheet [Member] | Institutional Credit [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[6]	0	[5]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[6]	0	[5],[7]
Investment Securities [Member] | On-balance sheet [Member] | Corporate [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	479,548,000	[6]	409,657,000	[5]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 482,757,000	[5],[6]	$ 412,690,000	[5],[7]

[1] Includes borrower remittances of $0.8 million. The borrower remittances have not been passed through to third party investors as of March 31, 2015.

[2] Includes unamortized premiums related to the Rural Utilities line of business of $3.7 million.

[3] Includes $0.4 million of unamortized premiums and discounts and fair value adjustments related to the USDA Guarantees line of business. Includes fair value adjustments related to the Institutional Credit line of business of $2.4 million.

[4] Includes borrower remittances of $2.9 million, which have not been passed through to third party investors as of December 31, 2014.

[5] Includes auction-rate certificates, asset-backed securities, and government-sponsored enterprise ("GSE")-guaranteed mortgage-backed securities.

[6] The amount under the Farm & Ranch line of business relates to unconsolidated trusts where Farmer Mac determined it was not the primary beneficiary due to shared power with an unrelated party.

[7] armer Mac uses unpaid principal balance and the outstanding face amount of investment securities to represent maximum exposure to loss.

[8] Farmer Mac uses unpaid principal balance and outstanding face amount of investment securities to represent maximum exposure to loss.

[9] Includes $0.2 million of unamortized premiums and discounts and fair value adjustments related to the USDA Guarantees line of business. Includes fair value adjustments related to the Institutional Credit line of business of $2.4 million.