Loans and Allowance for Losses and Concentrations of Credit Risk - Concentrations of Credit Risk (Details) - USD ($) $ in Thousands		3 Months Ended
		Sep. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1],[2]	$ 6,004,728	$ 5,725,299
Financing Receivables, Original Loan-To-Value Ratio, Range One [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 1,687,390	1,594,818
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		$ 1,379,453	1,279,321
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		$ 1,662,645	1,593,025
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		$ 1,087,226	1,107,710
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		$ 164,868	126,860
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		$ 23,146	23,565
Financing Receivables, Loan-To-Value Ratio Range, Lower Range Limit		80.01%
Financing Receivables, Loan-To-Value Ratio Range, Upper Range Limit		90.00%
Northwest [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	$ 616,869	582,127
Southwest [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	1,796,800	1,726,927
Mid-North [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	2,051,860	2,009,654
Mid-South [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	824,236	769,831
Northeast [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	225,068	215,883
Southeast [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	489,895	420,877
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	3,372,582	3,243,651
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	1,018,098	941,411
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	1,263,133	1,236,781
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	292,680	211,125
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	44,632	81,990
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	$ 13,603	$ 10,341

[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).