CONSOLIDATED STATEMENTS OF EQUITY Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Class C, Non-Voting [Member]	Preferred Stock [Member]	Preferred Stock [Member] Common Class C, Non-Voting [Member]	Common Stock [Member]	Common Stock [Member] Common Class C, Non-Voting [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Common Class C, Non-Voting [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Common Class C, Non-Voting [Member]	Retained Earnings [Member]	Retained Earnings [Member] Common Class C, Non-Voting [Member]	Noncontrolling Interest [Member]	Noncontrolling Interest [Member] Common Class C, Non-Voting [Member]
Beginning Balance (Shares Outstanding) at Dec. 31, 2016			8,400		10,539
Beginning Balance at Dec. 31, 2016	$ (643,647)		$ (204,759)		$ (10,539)		$ (118,655)		$ (33,758)		$ (275,714)		$ (222)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Attributable to Farmer Mac	21,910		0		0		0		0		21,910		0
Less: Net loss attributable to non-controlling interest	15		0		0		0		0		0		(15)
Other comprehensive income, net of tax	7,786		0		0		0		7,786		0		0
Preferred stock	(3,295)		0		0		0		0		(3,295)		0
Common stock	(3,799)		0		0		0		0		(3,799)		0
Stock Issued During Period, Shares, New Issues				0		57
Stock Issued During Period, Value, New Issues		$ 201		$ 0		$ 57		$ 144		$ 0		$ 0		$ 0
Stock-based compensation cost	981		0		0		981		0		0		0
Other stock-based award activity	(1,394)		$ 0		$ 0		(1,394)		0		0		0
Ending Balance (Shares Outstanding) at Mar. 31, 2017			8,400		10,596
Ending Balance at Mar. 31, 2017	666,022		$ 204,759		$ 10,596		118,386		41,544		290,530		207
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	498		0		0		0		27		471		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	708,644		$ 204,759		$ 10,619		118,979		51,112		323,175		0
Beginning Balance (Shares Outstanding) at Dec. 31, 2017			8,400		10,619
Beginning Balance at Dec. 31, 2017	(708,146)		$ (204,759)		$ (10,619)		(118,979)		(51,085)		(322,704)		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Attributable to Farmer Mac	25,819		0		0		0		0		25,819		0
Less: Net loss attributable to non-controlling interest	0
Other comprehensive income, net of tax	20,999		0		0		0		20,999		0		0
Preferred stock	(3,295)		0		0		0		0		(3,295)		0
Common stock	(6,161)		0		0		0		0		(6,161)		0
Stock Issued During Period, Shares, New Issues				0		31
Stock Issued During Period, Value, New Issues		$ 34		$ 0		$ 31		$ 3		$ 0		$ 0		$ 0
Stock-based compensation cost	664		0		0		664		0		0		0
Other stock-based award activity	(1,438)		$ 0		$ 0		(1,438)		0		0		0
Ending Balance (Shares Outstanding) at Mar. 31, 2018			8,400		10,650
Ending Balance at Mar. 31, 2018	$ 745,266		$ 204,759		$ 10,650		$ 118,208		$ 72,111		$ 339,538		$ 0