Loans and Allowance for Losses and Concentrations of Credit Risk Loan (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 2,744,242	[1]	$ 2,711,796	[1]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	29,651		35,272
Lower of Cost or Fair Value Adjustment on Loans Held for Sale	0		(5,943)
Loans Held for Investment and Loans in Consolidated Trusts, at Amortized Cost	2,773,893		2,067,134
Loans held for sale, at lower of cost or fair value	0		673,991
Loans and Leases Receivable, Net of Deferred Income	2,773,893		2,741,125
Allowance for Loan and Lease Losses, Real Estate	(7,967)		(11,351)
Total loans, net of allowance	2,765,926		2,729,774
Farm & Ranch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,704,544		1,679,851
Rural Utilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,039,698		1,031,945
Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	527,930	[1]	529,284	[1]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	33,752		34,291
Lower of Cost or Fair Value Adjustment on Loans Held for Sale	0		0
Loans Held for Investment and Loans in Consolidated Trusts, at Amortized Cost	561,682		563,575
Loans held for sale, at lower of cost or fair value	0		0
Loans and Leases Receivable, Net of Deferred Income	561,682		563,575
Allowance for Loan and Lease Losses, Real Estate	(324)		(365)
Total loans, net of allowance	561,358		563,210
Variable Interest Entity, Primary Beneficiary [Member] | Farm & Ranch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	166,163		160,436
Variable Interest Entity, Primary Beneficiary [Member] | Rural Utilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	361,767		368,848
Unsecuritized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	2,216,312	[1]	2,182,512	[1]
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	(4,101)		981
Lower of Cost or Fair Value Adjustment on Loans Held for Sale	0		(5,943)
Loans Held for Investment and Loans in Consolidated Trusts, at Amortized Cost	2,212,211		1,503,559
Loans held for sale, at lower of cost or fair value	0		673,991
Loans and Leases Receivable, Net of Deferred Income	2,212,211		2,177,550
Allowance for Loan and Lease Losses, Real Estate	(7,643)		(10,986)
Total loans, net of allowance	2,204,568		2,166,564
Unsecuritized [Member] | Farm & Ranch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,538,381		1,519,415
Unsecuritized [Member] | Rural Utilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 677,931		$ 663,097

[1] 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".