Loans and Allowance for Losses and Concentrations of Credit Risk - Concentrations of Credit Risk (Details) - USD ($) $ in Thousands		3 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1],[2]	$ 5,504,030	$ 5,417,174
Northwest [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	579,240	573,135
Southwest [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	1,693,048	1,753,606
Mid-North [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	1,933,020	1,873,041
Mid-South [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	688,615	627,615
Northeast [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	211,093	214,402
Southeast [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	399,014	375,375
Financing Receivables, Original Loan-To-Value Ratio, Range One [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 1,538,701	1,503,076
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		0.00%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		40.00%
Financing Receivables, Original Loan-To-Value Ratio, Range Two [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 1,193,443	1,191,804
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		40.01%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		50.00%
Financing Receivables, Original Loan-To-Value Ratio, Range Three [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 1,536,435	1,491,502
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		50.01%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		60.00%
Financing Receivables, Original Loan-To-Value Ratio, Range Four [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 1,072,182	1,091,759
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		60.01%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		70.00%
Financing Receivables, Original Loan-To-Value Ratio, Range Five [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 136,641	115,645
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		70.01%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		80.00%
Financing Receivables, Original Loan-To-Value Ratio, Range Six [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 26,628	23,388
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		80.01%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		90.00%
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	$ 3,054,452	2,941,266
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	930,659	920,195
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	1,210,417	1,260,618
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	211,565	173,954
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	91,099	114,360
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	$ 5,838	$ 6,781

[1] Amounts represent unpaid principal balance of risk-rated loans, which is the basis Farmer Mac uses to analyze its portfolio, and recorded investment of past due loans.

[2] Geographic regions: Northwest (AK, ID, MT, OR, WA, WY); Southwest (AZ, CA, CO, HI, NM, NV, UT); Mid-North (IA, IL, IN, MI, MN, NE, ND, SD, WI); Mid-South (AR, KS, LA, MO, OK, TX); Northeast (CT, DE, KY, MA, MD, ME, NH, NJ, NY, OH, PA, RI, VA, VT, WV); Southeast (AL, FL, GA, MS, NC, SC, TN).