Loans and Allowance for Losses and Concentrations of Credit Risk - Concentrations of Credit Risk (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1],[2]	$ 6,426,518	$ 6,139,304
Financing Receivables, Original Loan-To-Value Ratio, Range One [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross		$ 1,250,561	1,220,432
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		$ 1,607,806	1,466,047
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		$ 2,170,648	2,078,099
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		$ 1,149,539	1,167,395
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		$ 220,932	191,664
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		$ 27,032	15,667
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]	$ 706,366	657,403
Southwest [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	1,898,171	1,791,745
Mid-North [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	2,196,291	2,104,867
Mid-South [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	860,428	837,121
Northeast [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	259,254	229,679
Southeast [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[2]	506,008	518,489
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	3,528,351	3,410,498
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	1,149,560	1,037,440
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	1,298,651	1,305,844
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	382,744	324,074
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	53,999	48,051
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Gross	[1]	$ 13,213	$ 13,397

[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).