Accounting Policies - Variable Interest Entities (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 563,855,000		$ 563,575,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	178,076,000		167,621,000
Other Liabilities	1,200,000	[1]	7,200,000
On-balance sheet [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	563,855,000	[2]	563,575,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	178,076,000	[1]	167,621,000
On-balance sheet [Member] | Farm & Ranch [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	176,921,000	[2]	160,436,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	178,076,000	[1]	167,621,000	[3]
On-balance sheet [Member] | USDA Guarantees [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	[2]	0
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	0	[1]	0
On-balance sheet [Member] | Rural Utilities [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	386,934,000	[2]	403,139,000	[4]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	0	[1]	0
Investments [Member] | On-balance sheet [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	[2]	0
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	0	[1]	0
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	59,212,000	[5]	58,051,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	54,925,000	[6]	56,238,000	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	723,901,000		724,893,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	727,248,000	[6]	737,148,000	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | Farm & Ranch [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	33,504,000	[5]	31,370,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000,000	[6]	30,000,000	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | Farm & Ranch [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0		0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6]	0	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | USDA Guarantees [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	25,708,000	[5]	26,681,000	[8]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	24,925,000	[6]	26,238,000	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | USDA Guarantees [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0		0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6]	0	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | Rural Utilities [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[5]	0	[8]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6]	0	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | On-balance sheet [Member] | Rural Utilities [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0		0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6]	0	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Off-balance sheet [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,792,797,000	[6],[9]	1,911,028,000	[10],[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Off-balance sheet [Member] | Farm & Ranch [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,771,703,000	[6],[9]	1,881,370,000	[10],[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Off-balance sheet [Member] | USDA Guarantees [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	21,094,000	[6],[9]	29,658,000	[10],[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Off-balance sheet [Member] | Rural Utilities [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6],[9]	0	[10],[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Investments [Member] | On-balance sheet [Member] | Farmer Mac Guaranteed Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	[5]	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6]	0	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Investments [Member] | On-balance sheet [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	723,901,000		724,893,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	727,248,000	[6]	737,148,000	[7]
Variable Interest Entity, Not Primary Beneficiary [Member] | Investments [Member] | Off-balance sheet [Member] | Investment Securities Trusts [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[6],[9]	0	[10],[7]
USDA Guarantees [Member]
Noncontrolling Interest [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	800,000	[5]	400,000
Farm & Ranch [Member]
Noncontrolling Interest [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	3,500,000	[5]	1,400,000
Rural Utilities [Member]
Noncontrolling Interest [Line Items]
Debt Instrument, Unamortized Premium	32,700,000	[11]	34,300,000
Shared power with unrelated party [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Farm & Ranch [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 801,700,000		$ 911,400,000

[1] Includes borrower remittances of $1.2 million, which have not been passed through to third party investors as of September 30, 2013.

[2] Unpaid principal balance is the basis of presentation in disclosures of outstanding balances for Farmer Mac's lines of business. See "Management's Discussion and Analysis—Results of Operations—Business Volume."

[3] Includes borrower remittances of $7.2 million, which have not been passed through to third party investors as of December 31, 2012.

[4] Includes unamortized premiums related to Rural Utilities of $34.3 million.

[5] Includes unamortized premiums and discounts and fair value adjustments related to Farm & Ranch and USDA Guarantees of $3.5 million and $0.8 million, respectively.

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

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

[8] Includes unamortized premiums and discounts and fair value adjustments related to Farm & Ranch and USDA Guarantees of $1.4 million and $0.4 million, respectively.

[9] Of the Farm & Ranch amount, $801.7 million relates to unconsolidated trusts where Farmer Mac determined it was not the primary beneficiary due to shared power with an unrelated party.

[10] Of the Farm & Ranch amount, $911.4 million relates to unconsolidated trusts where Farmer Mac determined it was not the primary beneficiary due to shared power with an unrelated party.

[11] Includes unamortized premiums related to Rural Utilities of $32.7 million.