CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 781,829	$ 574,469	$ 781,829	$ 574,469	$ 592,962
Net income attributable to Farmer Mac	8,943	13,367	48,090	75,328	46,773
Balance, end of period	781,829	574,469	781,829	574,469	592,962
Other comprehensive income/(loss), net of tax			31,735	(90,171)	(5,401)
Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period (Shares)	8,400	2,400	8,400	2,400	58	58
Balance, beginning of period	204,759	58,333	204,759	58,333	57,578	57,578
Balance, end of period	204,759	58,333	204,759	58,333	57,578	57,578
Balance, end of period (Shares)	8,400	2,400	8,400	2,400	58	58
Preferred Stock [Member] | Series A Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Series preferred stock (Shares)			0	2,400	0
Issuance of Series preferred stock			0	58,333	0
Issuance of Class C common stock (Shares)			0	2,400	0
Issuance of Class C common stock			0	58,333	0
Preferred Stock [Member] | Series B Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Series preferred stock (Shares)			3,000	0	0
Issuance of Series preferred stock			73,044	0	0
Issuance of Class C common stock (Shares)			3,000	0	0
Issuance of Class C common stock			73,044	0	0
Preferred Stock [Member] | Series C Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Series preferred stock (Shares)			3,000	0	0
Issuance of Series preferred stock			73,382	0	0
Issuance of Class C common stock (Shares)			3,000	0	0
Issuance of Class C common stock			73,382	0	0
Preferred Stock [Member] | Retired Series C Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of Series C preferred stock (Shares)			0	(58)	0
Redemption of Series C preferred stock			0	(57,578)	0
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period (Shares)	10,937	10,886	10,937	10,886	10,702	10,357
Balance, beginning of period	10,937	10,886	10,937	10,886	10,702	10,357
Issuance of Series preferred stock (Shares)			51	184	345
Issuance of Series preferred stock			51	184	345
Issuance of Class C common stock (Shares)			51	184	345
Issuance of Class C common stock			51	184	345
Balance, end of period	10,937	10,886	10,937	10,886	10,702	10,357
Balance, end of period (Shares)	10,937	10,886	10,937	10,886	10,702	10,357
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	113,559	110,722	113,559	110,722	106,617	102,821
Issuance of Series preferred stock			19	25	14
Issuance of Class C common stock			19	25	14
Stock-based compensation expense			2,859	2,966	2,428
Tax effect of stock-based awards			(41)	1,114	1,354
Balance, end of period	113,559	110,722	113,559	110,722	106,617	102,821
Retained Earnings [Member}
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	201,013	168,877	201,013	168,877	102,243	62,554
Net income attributable to Farmer Mac			48,090	75,328	46,773
Balance, end of period	201,013	168,877	201,013	168,877	102,243	62,554
Cash dividends:
Common stock ($0.56 per share in 2014, $0.48 per share in 2013, and $0.40 per share in 2012)			(6,115)	(5,199)	(4,205)
Retained Earnings [Member} | Series A Preferred Stock [Member]
Cash dividends:
Preferred Stock Series A ($1.4688 per share in 2014 and $1.3994 per share in 2013) Preferred stock, Series B ($1.3129 per share), Preferred stock Series C ($0.7917 per share), Preferred stock, retired Series C ($2.36 in 2013 per share and $50 per share in 2012)			(3,525)	(3,359)	0
Retained Earnings [Member} | Series B Preferred Stock [Member]
Cash dividends:
Preferred Stock Series A ($1.4688 per share in 2014 and $1.3994 per share in 2013) Preferred stock, Series B ($1.3129 per share), Preferred stock Series C ($0.7917 per share), Preferred stock, retired Series C ($2.36 in 2013 per share and $50 per share in 2012)			(3,939)	0	0
Retained Earnings [Member} | Series C Preferred Stock [Member]
Cash dividends:
Preferred Stock Series A ($1.4688 per share in 2014 and $1.3994 per share in 2013) Preferred stock, Series B ($1.3129 per share), Preferred stock Series C ($0.7917 per share), Preferred stock, retired Series C ($2.36 in 2013 per share and $50 per share in 2012)			(2,375)	0	0
Retained Earnings [Member} | Retired Series C Preferred Stock [Member]
Cash dividends:
Preferred Stock Series A ($1.4688 per share in 2014 and $1.3994 per share in 2013) Preferred stock, Series B ($1.3129 per share), Preferred stock Series C ($0.7917 per share), Preferred stock, retired Series C ($2.36 in 2013 per share and $50 per share in 2012)			0	(136)	(2,879)
Accumulated Other Comprehensive Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	15,533	(16,202)	15,533	(16,202)	73,969	79,370
Balance, end of period	15,533	(16,202)	15,533	(16,202)	73,969	79,370
Other comprehensive income/(loss), net of tax			31,735	(90,171)	(5,401)
Total Stockholders Equity [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	545,801	332,616	545,801	332,616	351,109
Balance, end of period	545,801	332,616	545,801	332,616	351,109
Non-controlling Interest - Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	236,028	241,853	236,028	241,853	241,853	241,853
Balance, end of period	236,028	241,853	236,028	241,853	241,853	241,853
Investment in Contour - origination of a non-controlling interest			175	0	0
Purchase of non-controlling interest - preferred stock			$ (6,000)	$ 0	$ 0