Accounting Policies - Principles of Consolidation (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2015 USD ($) subsidiary		Dec. 31, 2014 USD ($)
Variable Interest Entity [Line Items]
Number of Subsidiaries | subsidiary	3
Loans held for investment in consolidated trusts, at amortized cost	$ 612,567		$ 692,478
Debt securities of consolidated trusts held by third parties	612,994		424,214
Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Other Liabilities	400		2,900
USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	(500)		(200)
Rural Utilities [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)			(3,700)
Institutional Credit [Member]
Variable Interest Entity [Line Items]
Fair Value Adjustment	1,800		2,400
On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	612,567	[1]	692,478	[2]
Debt securities of consolidated trusts held by third parties	612,994	[3]	424,214	[4]
On-balance sheet [Member] | Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	612,567	[1]	421,355	[2]
Debt securities of consolidated trusts held by third parties	612,994	[3]	424,214	[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	[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	1,534,181	[5]	1,620,064	[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	553,469	[5]	636,086	[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	10,712	[5]	13,978	[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	[5]	970,000	[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	62,541	[8]	60,035	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	61,218	[5]	57,832	[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	30,708	[8]	27,620	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	31,218	[5]	27,832	[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	31,833	[8]	32,415	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000	[5]	30,000	[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)	(6,679)		(7,471)
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	539,828	[10]	409,657	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	538,462	[5],[10]	412,690	[7],[11]
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	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[10]	0	[7],[11]
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	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[10]	0	[7],[11]
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	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[10]	0	[7],[11]
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	[10]	0	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5],[10]	0	[7],[11]
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	539,828	[10]	409,657	[11]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 538,462	[5],[10]	$ 412,690	[7],[11]

[1] Includes borrower remittances of $0.4 million which have not been passed through to third party investors as of September 30, 2015.

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

[3] Includes $0.5 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 $1.8 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.

[10] 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.

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