Accounting Policies - Consolidation of Variable Interest Entities (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	$ 692,478,000		$ 629,989,000
Debt securities of consolidated trusts held by third parties	424,214,000		261,760,000
On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	692,478,000	[1]	629,989,000	[2]
Debt securities of consolidated trusts held by third parties	424,214,000	[3]	261,760,000	[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	1,620,064,000	[5],[6]	1,755,973,000	[6],[7]
Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Other Liabilities	2,900,000		2,300,000
Farm & Ranch [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	421,355,000	[1]	259,509,000	[2]
Debt securities of consolidated trusts held by third parties	424,214,000	[3]	261,760,000	[4]
Farm & Ranch [Member] | 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	636,086,000	[5],[6]	765,751,000	[6],[7]
USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	(200,000)		100,000
USDA Guarantees [Member] | On-balance sheet [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]
USDA Guarantees [Member] | 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	13,978,000	[5],[6]	20,222,000	[6],[7]
Rural Utilities [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Unamortized Premium	3,700,000		16,200,000
Rural Utilities [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	271,123,000	[1]	370,480,000	[2]
Debt securities of consolidated trusts held by third parties	0	[3]	0	[4]
Rural Utilities [Member] | 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	0	[5],[6]	0	[6],[7]
Institutional Credit [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	2,400,000		3,200,000
Institutional Credit [Member] | On-balance sheet [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]
Institutional Credit [Member] | 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	970,000,000	[5],[6]	970,000,000	[6],[7]
Corporate [Member] | On-balance sheet [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]
Corporate [Member] | 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	0	[5],[6]	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	60,035,000	[8]	54,482,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	57,832,000	[5]	51,088,000	[7]
Farmer Mac Guaranteed Securities: | Farm & Ranch [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	0	[8]	0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[7]
Farmer Mac Guaranteed Securities: | USDA Guarantees [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	27,620,000	[8]	21,234,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	27,832,000	[5]	21,088,000	[7]
Farmer Mac Guaranteed Securities: | Rural Utilities [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	0	[8]	0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]	0	[7]
Farmer Mac Guaranteed Securities: | Institutional Credit [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	32,415,000	[8]	33,248,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000,000	[5]	30,000,000	[7]
Farmer Mac Guaranteed Securities: | Corporate [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	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)	7,471,000		10,014,000
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	409,657,000	[10]	533,688,000	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	412,690,000	[10],[5]	540,726,000	[11],[7]
Investment Securities [Member] | Farm & Ranch [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	0	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]	0	[11],[7]
Investment Securities [Member] | USDA Guarantees [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	0	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]	0	[11],[7]
Investment Securities [Member] | Rural Utilities [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	0	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]	0	[11],[7]
Investment Securities [Member] | Institutional Credit [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	0	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]	0	[11],[7]
Investment Securities [Member] | Corporate [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	409,657,000	[10]	533,688,000	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 412,690,000	[10],[5]	$ 540,726,000	[11],[7]

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

[2] Includes unamortized premiums related to the Rural Utilities line of business of $16.2 million.

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

[4] Includes borrower remittances of $2.3 million, which have not been passed through to third party investors as of December 31, 2013.

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

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

[8] 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.

[9] Includes unamortized premiums and discounts and fair value adjustments related to the USDA Guarantees and Institutional Credit lines of business of $0.1 million and $3.2 million, respectively.

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

[11] Includes auction-rate certificates, asset-backed securities, and GSE-guaranteed mortgage-backed securities.