Related Party Transactions - Zions (Details) - Zions First National Bank [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Related Party's percent of Farmer Mac Total Outstanding Book of Business	5.70%	5.90%
Related Party Transaction, Expenses from Transactions with Related Party	$ 9,300	$ 8,400	$ 7,000
Sale of Farmer Mac Guaranteed Securities [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	255,338	147,234	120,409
Medium-term Notes [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 0	$ 5,000	$ 0
Farm & Ranch [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Related Party's Percent of Total Program Loans	23.90%	22.30%	25.50%
Related Party Transaction, Related Party's percent of total Program	15.20%	14.60%	15.40%
USDA Guarantee [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Related Party's percent of total Program	3.60%	12.40%	3.60%
Mortgage Loans on Real Estate [Member] | Farm & Ranch [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	$ 178,890	$ 155,808	$ 210,088
USDA Securities [Member] | USDA Guarantee [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	13,718	42,637	13,153
On-balance sheet [Member] | Farmer Mac Guaranteed Securities [Member] | Institutional Credit [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	$ 0	$ 50,237	$ 0
Common Class A, Voting [Member]
Related Party Transaction [Line Items]
Common Stock Ownership Percentage by a Related Party	31.20%