Loans and Allowance for Losses and Concentrations of Credit Risk - Loan (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment, at amortized cost	$ 2,689,531		$ 2,570,125
Allowance for Loan and Lease Losses, Real Estate	6,326		6,866
Total loans, net of allowance	3,353,345		3,193,248
Unsecuritized [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	2,692,698	[1]	2,573,968	[1]
Unamortized premiums, discounts and other cost basis adjustments	(3,167)		(3,843)
Loans held for investment, at amortized cost	2,689,531		2,570,125
Allowance for Loan and Lease Losses, Real Estate	5,837		6,587
Total loans, net of allowance	2,683,694		2,563,538
Unsecuritized [Member] | Farm & Ranch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	1,981,456		1,875,958
Unsecuritized [Member] | Rural Utilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	711,242		698,010
In Consolidated Trusts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	666,387	[1]	613,750	[1]
Unamortized premiums, discounts and other cost basis adjustments	3,753		16,239
Loans held for investment, at amortized cost	670,140		629,989
Allowance for Loan and Lease Losses, Real Estate	489		279
Total loans, net of allowance	669,651		629,710
In Consolidated Trusts | Farm & Ranch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	398,992		259,509
In Consolidated Trusts | Rural Utilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	267,395		354,241
Commercial Real Estate Other Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	3,359,085	[1]	3,187,718	[1]
Unamortized premiums, discounts and other cost basis adjustments	586		12,396
Loans held for investment, at amortized cost	3,359,671		3,200,114
Allowance for Loan and Lease Losses, Real Estate	6,326		6,866
Total loans, net of allowance	3,353,345		3,193,248
Commercial Real Estate Other Receivable [Member] | Farm & Ranch [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	2,380,448		2,135,467
Commercial Real Estate Other Receivable [Member] | Rural Utilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Lease Receivable Unpaid Principal Balance	$ 978,637		$ 1,052,251

[1] Unpaid principal balance is the basis of presentation in disclosures of outstanding balances for Farmer Mac's lines of business.