Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Interest and Dividend Income, Operating	$ 58,199	$ 60,882	$ 61,775	$ 49,718	$ 49,180	$ 62,975	$ 61,745	$ 61,498	$ 230,574	[1]	$ 235,398	[2]	$ 264,670	[2]
Total interest expense	44,606	48,886	42,502	34,726	35,777	34,787	33,584	33,128	170,720	[3]	137,276	[4]	142,690	[4]
Net interest income	13,593	11,996	19,273	14,992	13,403	28,188	28,161	28,370	59,854		98,122		121,980
Release of /(provision for) loan losses	(462)	511	(1,583)	573	117	(499)	(529)	430	(961)		(481)		3,691
Net interest income after release of/(provision for) loan losses	14,055	11,485	20,856	14,419	13,286	28,687	28,690	27,940	60,815		98,603		118,289
Guarantee and commitment fees	6,094	6,172	6,403	6,518	6,768	6,819	6,759	6,612	25,187		26,958		24,963
(Losses)/gains on financial derivatives and hedging activities	(9,178)	808	(5,698)	(7,578)	9,263	3,024	14,983	4,494
Gains/(losses) on trading securities	13,857	16,369	7,748	655	(76)	(626)	(327)	210	38,629		(819)		307
(Losses)/gains on sale of available-for-sale investment securities	0	(396)	143	15	(960)	0	3,071	2	(238)		2,113		18
Gains on repurchase of debt					1,462	0	0	0	0		1,462		0
Gains on sale of real estate owned	(28)	0	168	(3)	26	39	1,124	47	137		1,236		878
Other income	920	502	200	92	539	565	873	1,080	1,714		3,057		3,341
Non-interest income/(loss)	11,665	23,455	8,964	(301)	17,022	9,821	26,483	12,445	43,783		65,771		3,735
Noninterest Expense	8,594	7,095	7,856	7,947	7,621	8,441	7,964	9,081	31,492	[5]	33,107	[5]	30,908	[5]
Income before income taxes	17,126	27,845	21,964	6,171	22,687	30,067	47,209	31,304	73,106		131,267		91,116
Income tax expense	2,769	7,564	(6,368)	(1,141)	3,774	8,226	13,036	8,716	2,824		33,752		22,156
Net income	14,357	20,281	28,332	7,312	18,913	21,841	34,173	22,588	70,282		97,515		68,960
Net Income (Loss) Attributable to Noncontrolling Interest	5,414	5,412	5,819	5,547	5,546	5,547	5,547	5,547	22,192		22,187		22,187
Net income attributable to Farmer Mac	8,943	14,869	22,513	1,765	13,367	16,294	28,626	17,041	48,090		75,328		46,773
Preferred stock dividends	3,296	3,283	2,308	952	882	881	881	851	9,839		3,495		2,879
Net income attributable to common stockholders	$ 5,647	$ 11,586	$ 20,205	$ 813	$ 12,485	$ 15,413	$ 27,745	$ 16,190	$ 38,251		$ 71,833		$ 43,894
Basic earnings per common share	$ 0.52	$ 1.06	$ 1.85	$ 0.07	$ 1.14	$ 1.42	$ 2.57	$ 1.51	$ 3.50		$ 6.64		$ 4.19
Diluted earnings per common share	$ 0.50	$ 1.02	$ 1.78	$ 0.07	$ 1.11	$ 1.37	$ 2.48	$ 1.45	$ 3.37		$ 6.41		$ 3.98

[1] Includes reconciling adjustments for the amortization of premiums and discounts on assets consolidated at fair value to reflect core earnings amounts and interest income related to securities purchased under agreements to resell.

[2] Includes reconciling adjustments for the amortization of premiums and discounts on assets consolidated at fair value to reflect core earnings amounts.

[3] Based on effective funding cost determined for each operating segment, including expenses related to interest rate swaps not designated as hedges, which are included in "(Losses)/gains on financial derivatives and hedging activities" on the consolidated financial statements. Includes reconciling adjustments for interest expense related to securities sold, not yet purchased.

[4] Based on effective funding cost determined for each operating segment, including expenses related to interest rate swaps not designated as hedges, which are included in "(Losses)/gains on financial derivatives and hedging activities" on the consolidated financial statements.

[5] Includes directly attributable costs and an allocation of indirectly attributable costs based on headcount.