Accounting Policies - Principles of Consolidation (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Variable Interest Entity [Line Items]
Number of Subsidiaries	2
Loans held for investment in consolidated trusts, at amortized cost (1)	$ 670,140,000			$ 670,140,000			$ 629,989,000
Debt securities of consolidated trusts held by third parties (2)	400,012,000			400,012,000			261,760,000
Guarantee and commitment fees	6,172,000		6,819,000	19,093,000		20,190,000
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	1,630,427,000			1,630,427,000			0
Federal Funds Sold and Securities Purchased under Agreements to Resell Pledged as Collateral	1,600,000,000			1,600,000,000			0
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	1,600,000,000			1,600,000,000			0
On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost (1)	670,140,000	[1]		670,140,000	[1]		629,989,000	[2]
Debt securities of consolidated trusts held by third parties (2)	400,012,000	[3]		400,012,000	[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	1,662,507,000	[5],[6]		1,662,507,000	[5],[6]		1,755,973,000	[6],[7]
Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Other Liabilities	1,000,000			1,000,000			2,300,000
Guarantee and commitment fees	3,716,000		3,725,000	11,432,000		11,099,000
Farm & Ranch [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost (1)	398,992,000	[1]		398,992,000	[1]		259,509,000	[2]
Debt securities of consolidated trusts held by third parties (2)	400,012,000	[3]		400,012,000	[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	677,814,000			677,814,000			765,751,000
USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	0			0			100,000
Guarantee and commitment fees	49,000		30,000	98,000		105,000
USDA Guarantees [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost (1)	0	[1]		0	[1]		0	[2]
Debt securities of consolidated trusts held by third parties (2)	0	[3]		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	14,693,000	[5],[6]		14,693,000	[5],[6]		20,222,000	[6],[7]
Rural Utilities [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Unamortized Premium	3,800,000			3,800,000			16,200,000
Guarantee and commitment fees	0		0	0		948,000
Rural Utilities [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost (1)	271,148,000	[1]		271,148,000	[1]		370,480,000
Debt securities of consolidated trusts held by third parties (2)	0	[3]		0	[3]		0
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	[5],[6]		0
Institutional Credit [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	2,600,000			2,600,000			3,200,000
Guarantee and commitment fees	2,915,000		3,291,000	9,115,000		8,640,000
Institutional Credit [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost (1)	0	[1]		0	[1]		0	[2]
Debt securities of consolidated trusts held by third parties (2)	0	[3]		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	[5],[6]		970,000,000	[6],[7]
Corporate [Member]
Variable Interest Entity [Line Items]
Guarantee and commitment fees	0		0	0		0
Corporate [Member] | On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost (1)	0	[1]		0	[1]		0	[2]
Debt securities of consolidated trusts held by third parties (2)	0	[3]		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	[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	53,080,000	[8]		53,080,000	[8]		54,482,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	50,449,000	[5]		50,449,000	[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	[8]		0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]		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	20,449,000	[8]		20,449,000	[8]		21,234,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	20,449,000	[5]		20,449,000	[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			0			0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0			0			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	32,631,000	[8]		32,631,000	[8]		33,248,000	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000,000	[5]		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			0			0	[9]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[5]		0	[5]		0	[7]
Investment Securities [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	7,717,000			7,717,000			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	447,550,000	[10]		447,550,000	[10]		533,688,000	[7]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	450,505,000	[10],[5]		450,505,000	[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	[10]		0	[7]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]		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	[10]		0	[7]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]		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			0			0	[7]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]		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	[10]		0	[7]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[10],[5]		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	447,550,000			447,550,000			533,688,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	450,505,000			450,505,000			540,726,000	[11],[7]
FMMSC [Member]
Variable Interest Entity [Line Items]
Guarantee and commitment fees	$ 2,400,000		$ 2,800,000	$ 7,700,000		$ 8,200,000

[1] (1) Includes unamortized premiums related to the Rural Utilities line of business of $3.8 million.

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

[3] (2) Includes borrower remittances of $1.0 million. The borrower remittances have not been passed through to third party investors as of September 30, 2014.

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

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

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

[8] (3) Includes an immaterial amount of unamortized premiums and discounts related to the USDA Guarantees line of business. Includes fair value adjustments related to the Institutional Credit line of business of $2.6 million.

[9] (3) 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] (5) Includes auction-rate certificates, asset-backed securities, and government-sponsored enterprise ("GSE")-guaranteed mortgage-backed securities.

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