Accounting Policies Variable Interest Entities (Details) (USD $)	Mar. 31, 2013		Dec. 31, 2012
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 561,682,000		$ 563,575,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	167,250,000		167,621,000
Other Liabilities	1,100,000		7,200,000
On-balance sheet [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	561,682,000	[1]	563,575,000	[1]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	167,250,000	[2]	167,621,000	[2]
On-balance sheet [Member] | Farm & Ranch [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	166,162,000	[1]	160,436,000	[1]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	167,250,000	[2]	167,621,000	[2]
On-balance sheet [Member] | USDA Guarantees [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	[1]	0	[1]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	0	[2]	0	[2]
On-balance sheet [Member] | Rural Utilities [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	395,520,000	[1]	403,139,000	[1]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	0	[2]	0	[2]
Investments [Member] | On-balance sheet [Member]
Noncontrolling Interest [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0	[1]	0	[1]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	0	[2]	0	[2]
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	58,543,000	[3]	58,051,000	[3]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	55,852,000	[4]	56,238,000	[4]
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	699,591,000		724,893,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	708,317,000	[4]	737,148,000	[4]
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	31,345,000	[3]	31,370,000	[3]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000,000	[4]	30,000,000	[4]
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	[4]	0	[4]
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	27,198,000	[3]	26,681,000	[3]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	25,852,000	[4]	26,238,000	[4]
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	[4]	0	[4]
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	[3]	0	[3]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[4]	0	[4]
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	[4]	0	[4]
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	1,852,080,000	[4],[5]	1,911,028,000	[4],[5]
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	1,826,499,000	[4],[5]	1,881,370,000	[4],[5]
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	25,581,000	[4],[5]	29,658,000	[4],[5]
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	[4],[5]	0	[4],[5]
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	[3]	0	[3]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	[4]	0	[4]
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	699,591,000		724,893,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	708,317,000	[4]	737,148,000	[4]
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	[4],[5]	0	[4],[5]
USDA Guarantees [Member]
Noncontrolling Interest [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	1,300,000		400,000
Farm & Ranch [Member]
Noncontrolling Interest [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	1,300,000		1,400,000
Rural Utilities [Member]
Noncontrolling Interest [Line Items]
Debt Instrument, Unamortized Premium	33,800,000		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	$ 856,500,000		$ 911,400,000

[1] Includes unamortized premiums related to Rural Utilities of $33.8 million.

[2] Includes borrower remittances of $1.1 million, which have not been passed through to third party investors as of March 31, 2013.

[3] Includes unamortized premiums and discounts and fair value adjustments related to Farm & Ranch and USDA Guarantees of $1.3 million and $1.3 million, respectively.

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

[5] Of the Farm & Ranch amount, $856.5 million relates to unconsolidated trusts where Farmer Mac determined it was not the primary beneficiary due to shared power with an unrelated party.