Business Segment Reporting - Core Earnings - Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income	$ 67,562	$ 66,918	$ 66,392	$ 63,951	$ 60,730	$ 63,410	$ 64,475	$ 52,452	$ 264,823	[1]	$ 241,067	[2]	$ 246,729	[2]
Interest Income Reclassification									0		0		0
Total interest expense	(36,591)	(34,735)	(34,528)	(33,162)	(44,606)	(48,886)	(42,502)	(34,726)	(139,016)	[3]	(170,720)	[4]	(137,276)	[4]
Net effective spread	30,971	32,183	31,864	30,789	16,124	14,524	21,973	17,726	125,807		70,347		109,453
Guarantee and commitment fees	3,780	3,532	3,388	3,377	3,563	3,644	3,703	3,784	14,077		14,694		15,627
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									6,064	[5]	18,596	[6]	38,813	[6]
Non-interest income	6,440	(4,981)	18,207	475	9,134	20,927	6,264	(3,035)	20,141		33,290		54,440
(Provision for)/release of allowance for loan losses	(3,366)	1,164	(110)	(76)	462	(511)	1,583	(573)	(2,388)		961		481
(Release of)/provision for reserve for losses									2,180		2,205		(929)
Noninterest Expense, Excluding Loan, Lease and Other Losses									(37,662)		(33,697)		(32,178)
Non-interest expense	(5,865)	(10,421)	(10,853)	(8,343)	(8,594)	(7,095)	(7,856)	(7,947)	(35,482)	[7]	(31,492)	[8]	(33,107)	[8]
Income before income taxes	28,180	17,945	39,108	22,845	17,126	27,845	21,964	6,171	108,078		73,106		131,267
Income tax expense	(9,912)	(6,327)	(13,769)	(4,231)	(2,769)	(7,564)	6,368	1,141	(34,239)		(2,824)		(33,752)
Net income	18,268	11,618	25,339	18,614	14,357	20,281	28,332	7,312	73,839		70,282		97,515
Preferred Stock Dividends, Income Statement Impact	(3,296)	(3,295)	(3,296)	(3,295)	(3,296)	(3,283)	(2,308)	(952)	(13,182)		(9,839)		(3,495)
Less: Net income attributable to non-controlling interest	60	36	119	(5,354)	(5,414)	(5,412)	(5,819)	(5,547)	(5,139)		(22,192)		(22,187)
Loss on retirement of preferred stock	0	0	0	(8,147)					(8,147)		0		0
Net Income (Loss) Available to Common Stockholders, Basic	15,032	$ 8,359	$ 22,162	$ 1,818	5,647	$ 11,586	$ 20,205	$ 813	47,371		38,251		71,833
Segment Reporting Information, Additional Information [Abstract]
Assets	15,540,354				14,287,821				15,540,354		14,287,821		13,361,780
On and Off Balance Sheet Program Assets, At Principal Balance	15,898,820				14,597,758				15,898,820		14,597,758		13,950,312
Farm & Ranch [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income									90,578	[1]	78,934	[2]	67,429	[2]
Interest Income Reclassification									(3,078)		(2,086)		(964)
Total interest expense									(48,696)	[3]	(45,025)	[4]	(32,062)	[4]
Net effective spread									38,804		31,823		34,403
Guarantee and commitment fees									15,076		15,107		14,944
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									1,040	[5]	762	[6]	2,244	[6]
Non-interest income									16,116		15,869		17,188
(Provision for)/release of allowance for loan losses									(2,388)		961		481
(Release of)/provision for reserve for losses									2,180		2,205		(929)
Noninterest Expense, Excluding Loan, Lease and Other Losses									(16,876)		(15,180)		(14,649)
Non-interest expense									(14,696)	[7]	(12,975)	[8]	(15,578)	[8]
Segment core earnings before income taxes									37,836		35,678		36,494
Income tax expense									(13,188)		(12,486)		(12,773)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									24,648		23,192		23,721
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest									0		0		0
Loss on retirement of preferred stock									0
Segment core earnings									24,648		23,192		23,721
Segment Reporting Information, Additional Information [Abstract]
Assets	3,041,386				2,611,401				3,041,386		2,611,401		2,190,224
On and Off Balance Sheet Program Assets, At Principal Balance	5,725,299				5,417,174				5,725,299		5,417,174		5,163,080
USDA Guarantees [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income									59,902	[1]	54,955	[2]	53,384	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(42,063)	[3]	(36,689)	[4]	(35,656)	[4]
Net effective spread									17,839		18,266		17,728
Guarantee and commitment fees									17		134		132
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									100	[5]	63	[6]	791	[6]
Non-interest income									117		197		923
(Provision for)/release of allowance for loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(3,449)		(2,955)		(2,904)
Non-interest expense									(3,449)	[7]	(2,955)	[8]	(2,904)	[8]
Segment core earnings before income taxes									14,507		15,508		15,747
Income tax expense									(5,176)		(5,430)		(5,511)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									9,331		10,078		10,236
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest									0		0		0
Loss on retirement of preferred stock									0
Segment core earnings									9,331		10,078		10,236
Segment Reporting Information, Additional Information [Abstract]
Assets	1,977,609				1,825,210				1,977,609		1,825,210		1,656,688
On and Off Balance Sheet Program Assets, At Principal Balance	1,918,277				1,798,034				1,918,277		1,798,034		1,687,117
Rural Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income									26,819	[1]	27,879	[2]	35,194	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(15,425)	[3]	(17,138)	[4]	(23,601)	[4]
Net effective spread									11,394		10,741		11,593
Guarantee and commitment fees									397		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									25	[5]	9	[6]	0	[6]
Non-interest income									422		9		0
(Provision for)/release of allowance for loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(3,364)		(3,130)		(3,100)
Non-interest expense									(3,364)	[7]	(3,130)	[8]	(3,100)	[8]
Segment core earnings before income taxes									8,452		7,620		8,493
Income tax expense									(2,947)		(2,668)		(2,973)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									5,505		4,952		5,520
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest									0		0		0
Loss on retirement of preferred stock									0
Segment core earnings									5,505		4,952		5,520
Segment Reporting Information, Additional Information [Abstract]
Assets	1,019,279				995,082				1,019,279		995,082		1,076,298
On and Off Balance Sheet Program Assets, At Principal Balance	1,530,990				985,609				1,530,990		985,609		1,052,251
Institutional Credit [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income									76,487	[1]	77,512	[2]	89,199	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(33,032)	[3]	(38,456)	[4]	(53,613)	[4]
Net effective spread									43,455		39,056		35,586
Guarantee and commitment fees									1,665		1,539		1,515
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									0	[5]	0	[6]	0	[6]
Non-interest income									1,665		1,539		1,515
(Provision for)/release of allowance for loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(2,109)		(1,891)		(1,774)
Non-interest expense									(2,109)	[7]	(1,891)	[8]	(1,774)	[8]
Segment core earnings before income taxes									43,011		38,704		35,327
Income tax expense									(15,054)		(13,548)		(12,364)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									27,957		25,156		22,963
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest									0		0		0
Loss on retirement of preferred stock									0
Segment core earnings									27,957		25,156		22,963
Segment Reporting Information, Additional Information [Abstract]
Assets	5,420,195				5,459,296				5,420,195		5,459,296		5,121,666
On and Off Balance Sheet Program Assets, At Principal Balance	6,724,254				6,396,941				6,724,254		6,396,941		6,047,864
Corporate Segment [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income									13,338	[1]	17,637	[2]	21,940	[2]
Interest Income Reclassification									0		0		0
Total interest expense									(5,450)	[3]	(3,830)	[4]	(4,668)	[4]
Net effective spread									7,888		13,807		17,272
Guarantee and commitment fees									0		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									(1,972)	[5]	(4,913)	[6]	1,622	[6]
Non-interest income									(1,972)		(4,913)		1,622
(Provision for)/release of allowance for loan losses									0		0		0
(Release of)/provision for reserve for losses									0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses									(11,864)		(10,541)		(9,751)
Non-interest expense									(11,864)	[7]	(10,541)	[8]	(9,751)	[8]
Segment core earnings before income taxes									(5,948)		(1,647)		9,143
Income tax expense									3,803		23,347		8,991
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									(2,145)		21,700		18,134
Preferred Stock Dividends, Income Statement Impact									(13,182)		(9,839)		(3,495)
Less: Net income attributable to non-controlling interest									(5,139)		(22,192)		(22,187)
Loss on retirement of preferred stock									0
Segment core earnings									(20,466)		(10,331)		(7,548)
Segment Reporting Information, Additional Information [Abstract]
Assets	4,081,885				3,396,832				4,081,885		3,396,832		3,316,904
Segment Reconciling Items [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest Income									(2,301)	[1]	(15,850)	[2]	(20,417)	[2]
Interest Income Reclassification									3,078		2,086		964
Total interest expense									5,650	[3]	(29,582)	[4]	12,324	[4]
Net effective spread									6,427		(43,346)		(7,129)
Guarantee and commitment fees									(3,078)		(2,086)		(964)
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees									6,871	[5]	22,675	[6]	34,156	[6]
Non-interest income									3,793		20,589		33,192
(Provision for)/release of allowance 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
Non-interest expense									0	[7]	0	[8]	0	[8]
Segment core earnings before income taxes									10,220	[9]	(22,757)	[10]	26,063	[10]
Income tax expense									(1,677)		7,961		(9,122)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends									8,543	[9]	(14,796)	[10]	16,941	[10]
Preferred Stock Dividends, Income Statement Impact									0		0		0
Less: Net income attributable to non-controlling interest									0		0		0
Loss on retirement of preferred stock									(8,147)
Segment core earnings									396	[9]	(14,796)	[10]	16,941	[10]
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.

[2] 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.

[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 "Gains/(losses) on financial derivatives and hedging activities" on the consolidated financial statements.

[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 "Gains/(losses) on financial derivatives and hedging activities" on the consolidated financial statements. Includes reconciling adjustments for interest expense related to securities sold, not yet purchased.

[5] 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.

[6] 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.

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

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

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

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