Business Segment Reporting - (Details) (USD $) In Thousands, 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
Segment Reporting Information, Profit (Loss) [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]
Interest Income Reclassification									0		0		0
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 effective spread	13,593	11,996	19,273	14,992	13,403	28,188	28,161	28,370	59,854		98,122		121,980
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
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									18,596	[5]	38,813	[6]	(21,228)	[6]
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
Release of/(provision for) loan losses	462	(511)	1,583	(573)	(117)	499	529	(430)	961		481		(3,691)
(Release of)/provision for reserve for losses									2,205		(929)		1,816
Noninterest Expense, Excluding Loan, Lease and Other Losses									(33,697)		(32,178)		(32,724)
Noninterest Expense	(8,594)	(7,095)	(7,856)	(7,947)	(7,621)	(8,441)	(7,964)	(9,081)	(31,492)	[7]	(33,107)	[7]	(30,908)	[7]
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
Preferred Stock Dividends, Income Statement Impact	(3,296)	(3,283)	(2,308)	(952)	(882)	(881)	(881)	(851)	(9,839)		(3,495)		(2,879)
Less: Net income attributable to non-controlling interest - preferred stock dividends	(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 common stockholders	5,647	11,586	20,205	813	12,485	15,413	27,745	16,190	38,251		71,833		43,894
Segment Reporting Information, Additional Information [Abstract]
Assets	14,287,821				13,361,780				14,287,821		13,361,780		12,622,201
On and Off Balance Sheet Program Assets, At Principal Balance	14,597,758				13,950,312				14,597,758		13,950,312		13,015,188
Farm & Ranch [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating									78,934	[1]	67,429	[2]	70,590	[2]
Interest Income Reclassification									(2,086)		(964)		(1,659)
Total interest expense									(45,025)	[3]	(32,062)	[4]	(36,390)	[4]
Net effective spread									31,823		34,403		32,541
Guarantee and commitment fees									15,107		14,944		14,292
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									762	[5]	2,244	[6]	2,427	[6]
Non-interest income/(loss)									15,869		17,188		16,719
Release of/(provision for) loan losses									961		481		(3,691)
(Release of)/provision for reserve for losses									2,205		(929)		1,816
Noninterest Expense, Excluding Loan, Lease and Other Losses									(15,180)		(14,649)		(14,836)
Noninterest Expense									(12,975)	[7]	(15,578)	[7]	(13,020)	[7]
Segment core earnings before income taxes									35,678		36,494		32,549
Income tax expense									(12,486)		(12,773)		(11,392)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									23,192		23,721		21,157
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest - preferred stock dividends									0		0		0
Segment core earnings									23,192		23,721		21,157
Segment Reporting Information, Additional Information [Abstract]
Assets	2,611,401				2,190,224				2,611,401		2,190,224		1,736,391
On and Off Balance Sheet Program Assets, At Principal Balance	5,417,174				5,163,080				5,417,174		5,163,080		4,747,289
USDA Guarantees [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating									54,955	[1]	53,384	[2]	56,815	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(36,689)	[3]	(35,656)	[4]	(38,761)	[4]
Net effective spread									18,266		17,728		18,054
Guarantee and commitment fees									134		132		163
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									63	[5]	791	[6]	599	[6]
Non-interest income/(loss)									197		923		762
Release of/(provision for) loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(2,955)		(2,904)		(2,773)
Noninterest Expense									(2,955)	[7]	(2,904)	[7]	(2,773)	[7]
Segment core earnings before income taxes									15,508		15,747		16,043
Income tax expense									(5,430)		(5,511)		(5,615)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									10,078		10,236		10,428
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest - preferred stock dividends									0		0		0
Segment core earnings									10,078		10,236		10,428
Segment Reporting Information, Additional Information [Abstract]
Assets	1,825,210				1,656,688				1,825,210		1,656,688		1,641,030
On and Off Balance Sheet Program Assets, At Principal Balance	1,798,034				1,687,117				1,798,034		1,687,117		1,615,579
Rural Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating									27,879	[1]	35,194	[2]	35,566	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(17,138)	[3]	(23,601)	[4]	(23,301)	[4]
Net effective spread									10,741		11,593		12,265
Guarantee and commitment fees									0		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									9	[5]	0	[6]	466	[6]
Non-interest income/(loss)									9		0		466
Release of/(provision for) loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(3,130)		(3,100)		(3,204)
Noninterest Expense									(3,130)	[7]	(3,100)	[7]	(3,204)	[7]
Segment core earnings before income taxes									7,620		8,493		9,527
Income tax expense									(2,668)		(2,973)		(3,334)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									4,952		5,520		6,193
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest - preferred stock dividends									0		0		0
Segment core earnings									4,952		5,520		6,193
Segment Reporting Information, Additional Information [Abstract]
Assets	995,082				1,076,298				995,082		1,076,298		1,080,045
On and Off Balance Sheet Program Assets, At Principal Balance	985,609				1,052,251				985,609		1,052,251		1,031,945
Institutional Credit [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating									67,019	[1]	77,868	[2]	88,801	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(38,456)	[3]	(53,613)	[4]	(64,942)	[4]
Net effective spread									28,563		24,255		23,859
Guarantee and commitment fees									12,032		12,846		12,167
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									0	[5]	0	[6]	0	[6]
Non-interest income/(loss)									12,032		12,846		12,167
Release of/(provision for) loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(1,891)		(1,774)		(1,834)
Noninterest Expense									(1,891)	[7]	(1,774)	[7]	(1,834)	[7]
Segment core earnings before income taxes									38,704		35,327		34,192
Income tax expense									(13,548)		(12,364)		(11,967)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									25,156		22,963		22,225
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest - preferred stock dividends									0		0		0
Segment core earnings									25,156		22,963		22,225
Segment Reporting Information, Additional Information [Abstract]
Assets	5,459,296				5,121,666				5,459,296		5,121,666		4,772,509
On and Off Balance Sheet Program Assets, At Principal Balance	6,396,941				6,047,864				6,396,941		6,047,864		5,620,375
Corporate [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating									17,637	[1]	21,940	[2]	24,729	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(3,830)	[3]	(4,668)	[4]	(4,891)	[4]
Net effective spread									13,807		17,272		19,838
Guarantee and commitment fees									0		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									(4,913)	[5]	1,622	[6]	(2,113)	[6]
Non-interest income/(loss)									(4,913)		1,622		(2,113)
Release of/(provision for) loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(10,541)		(9,751)		(10,077)
Noninterest Expense									(10,541)	[7]	(9,751)	[7]	(10,077)	[7]
Segment core earnings before income taxes									(1,647)		9,143		7,648
Income tax expense									23,347		8,991		7,057
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									21,700		18,134		14,705
Preferred Stock Dividends, Income Statement Impact									(9,839)		(3,495)		(2,879)
Less: Net income attributable to non-controlling interest - preferred stock dividends									(22,192)		(22,187)		(22,187)
Segment core earnings									(10,331)		(7,548)		(10,361)
Segment Reporting Information, Additional Information [Abstract]
Assets	3,396,832				3,316,904				3,396,832		3,316,904		3,392,226
Segment Reconciling Items [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating									(15,850)	[1]	(20,417)	[2]	(11,831)	[2]
Interest Income Reclassification									2,086		964		1,659
Total interest expense									(29,582)	[3]	12,324	[4]	25,595	[4]
Net effective spread									(43,346)		(7,129)		15,423
Guarantee and commitment fees									(2,086)		(964)		(1,659)
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									22,675	[5]	34,156	[6]	(22,607)	[6]
Non-interest income/(loss)									20,589		33,192		(24,266)
Release of/(provision for) loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									0		0		0
Noninterest Expense									0	[7]	0	[7]	0	[7]
Segment core earnings before income taxes									(22,757)	[8]	26,063	[8]	(8,843)	[8]
Income tax expense									7,961		(9,122)		3,095
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									(14,796)	[8]	16,941	[8]	(5,748)	[8]
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest - preferred stock dividends									0		0		0
Segment core earnings									(14,796)	[8]	16,941	[8]	(5,748)
Segment Reporting Information, Additional Information [Abstract]
Assets	0				0				0		0		0
On and Off Balance Sheet Program Assets, At Principal Balance	$ 0				$ 0				$ 0		$ 0		$ 0

[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 interest income and interest expense related to securities purchased under agreements to resell and securities sold, not yet purchased, respectively; reconciling adjustments for the reclassification of expenses related to interest rate swaps not designated as hedges and fair value adjustments on financial derivatives and trading assets; and a reconciling adjustment related to the recognition of deferred gains over the estimated lives of certain Farmer Mac Guaranteed Securities and USDA Securities.

[6] Includes reconciling adjustments for the reclassification of expenses related to interest rate swaps not designated as hedges and fair value adjustments on financial derivatives and trading assets. Also includes a reconciling adjustment related to the recognition of deferred gains over the estimated lives of certain Farmer Mac Guaranteed Securities and USDA Securities.

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

[8] Net adjustments to reconcile core earnings before income taxes; core earnings before preferred stock dividends and attribution of income to non-controlling interest - preferred stock dividends; and segment core earnings to corresponding income measures: income before income taxes, net income, and net income attributable to common stockholders, respectively.