Business Segment Reporting - Core Earnings - Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	$ 66,918	[1]	$ 63,410	[2]	$ 197,261	[3]	$ 180,337	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(34,735)	[5]	(48,886)	[6]	(102,425)	[7]	(126,114)	[8]
Net effective spread	32,183		14,524		94,836		54,223
Guarantee and commitment fees	3,532		3,644		10,297		11,131
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	(8,513)	[9]	17,283	[10]	3,404	[11]	13,025	[12]
Non-interest (loss)/income	(4,981)		20,927		13,701		24,156
Release of/(provision for) allowance for loan losses	1,164		(511)		978		499
(Release of)/provision for reserve for losses	(861)		1,315		(1,235)		2,188
Noninterest Expense, Excluding Loan, Lease and Other Losses	(9,560)		(8,410)		(28,382)		(25,086)
Non-interest expense	(10,421)	[13]	(7,095)	[14]	(29,617)	[15]	(22,898)	[16]
Income before income taxes	17,945		27,845		79,898		55,980
Income tax expense	6,327		7,564		24,327		55
Net income	11,618		20,281		55,571		55,925
Preferred Stock Dividends, Income Statement Impact	(3,295)		(3,283)		(9,886)		(6,543)
Less: Net loss/(income) attributable to non-controlling interest	36		(5,412)		(5,199)		(16,778)
Loss on retirement of preferred stock	0		0		(8,147)		0
Net income attributable to common stockholders	8,359		11,586		32,339		32,604
Segment Reporting Information, Additional Information [Abstract]
Assets	14,853,845		14,525,697		14,853,845		14,525,697		$ 14,287,821
On and Off Balance Sheet Program Assets, At Principal Balance	15,627,979		14,004,822		15,627,979		14,004,822
Farm & Ranch [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	22,805	[1]	20,052	[2]	66,932	[3]	57,988	[4]
Interest Income Reclassification	(796)		(508)		(2,128)		(1,552)
Total interest expense	(12,381)	[5]	(11,337)	[6]	(35,381)	[7]	(33,295)	[8]
Net effective spread	9,628		8,207		29,423		23,141
Guarantee and commitment fees	3,785		3,716		11,111		11,432
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	513	[9]	369	[10]	760	[11]	742	[12]
Non-interest (loss)/income	4,298		4,085		11,871		12,174
Release of/(provision for) allowance for loan losses	1,164		(511)		978		499
(Release of)/provision for reserve for losses	(861)		1,315		(1,235)		2,188
Noninterest Expense, Excluding Loan, Lease and Other Losses	(4,228)		(3,797)		(12,858)		(11,263)
Non-interest expense	(5,089)	[13]	(2,482)	[14]	(14,093)	[15]	(9,075)	[16]
Segment core earnings before income taxes	10,001		9,299		28,179		26,739
Income tax expense	3,500		3,255		9,862		9,358
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	6,501		6,044		18,317		17,381
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss/(income) attributable to non-controlling interest	0		0		0		0
Loss on retirement of preferred stock					0
Segment core earnings	6,501		6,044		18,317		17,381
Segment Reporting Information, Additional Information [Abstract]
Assets	2,856,097		2,428,603		2,856,097		2,428,603
On and Off Balance Sheet Program Assets, At Principal Balance	5,504,030		5,314,437		5,504,030		5,314,437
USDA Guarantees [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	15,329	[1]	14,183	[2]	44,456	[3]	40,449	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(10,699)	[5]	(9,110)	[6]	(31,135)	[7]	(27,433)	[8]
Net effective spread	4,630		5,073		13,321		13,016
Guarantee and commitment fees	7		49		9		98
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	13	[9]	13	[10]	100	[11]	49	[12]
Non-interest (loss)/income	20		62		109		147
Release of/(provision for) allowance for loan losses	0		0		0		0
(Release of)/provision for reserve for losses	0		0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(986)		(747)		(2,396)		(2,242)
Non-interest expense	(986)	[13]	(747)	[14]	(2,396)	[15]	(2,242)	[16]
Segment core earnings before income taxes	3,664		4,388		11,034		10,921
Income tax expense	1,282		1,535		3,861		3,823
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	2,382		2,853		7,173		7,098
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss/(income) attributable to non-controlling interest	0		0		0		0
Loss on retirement of preferred stock					0
Segment core earnings	2,382		2,853		7,173		7,098
Segment Reporting Information, Additional Information [Abstract]
Assets	1,941,166		1,772,333		1,941,166		1,772,333
On and Off Balance Sheet Program Assets, At Principal Balance	1,898,625		1,759,948		1,898,625		1,759,948
Rural Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	6,909	[1]	6,703	[2]	20,015	[3]	21,228	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(4,002)	[5]	(3,813)	[6]	(11,466)	[7]	(13,395)	[8]
Net effective spread	2,907		2,890		8,549		7,833
Guarantee and commitment fees	100		0		100		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	0	[9]	9	[10]	0	[11]	9	[12]
Non-interest (loss)/income	100		9		100		9
Release of/(provision for) allowance for loan losses	0		0		0		0
(Release of)/provision for reserve for losses	0		0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(838)		(762)		(2,564)		(2,369)
Non-interest expense	(838)	[13]	(762)	[14]	(2,564)	[15]	(2,369)	[16]
Segment core earnings before income taxes	2,169		2,137		6,085		5,473
Income tax expense	760		749		2,129		1,917
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	1,409		1,388		3,956		3,556
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss/(income) attributable to non-controlling interest	0		0		0		0
Loss on retirement of preferred stock					0
Segment core earnings	1,409		1,388		3,956		3,556
Segment Reporting Information, Additional Information [Abstract]
Assets	987,115		981,300		987,115		981,300
On and Off Balance Sheet Program Assets, At Principal Balance	1,500,307		978,637		1,500,307		978,637
Institutional Credit [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	19,341	[1]	18,751	[2]	58,676	[3]	59,206	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(8,070)	[5]	(8,928)	[6]	(26,120)	[7]	(30,020)	[8]
Net effective spread	11,271		9,823		32,556		29,186
Guarantee and commitment fees	436		387		1,205		1,153
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	0	[9]	0	[10]	0	[11]	0	[12]
Non-interest (loss)/income	436		387		1,205		1,153
Release of/(provision for) allowance for loan losses	0		0		0		0
(Release of)/provision for reserve for losses	0		0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(522)		(478)		(1,589)		(1,415)
Non-interest expense	(522)	[13]	(478)	[14]	(1,589)	[15]	(1,415)	[16]
Segment core earnings before income taxes	11,185		9,732		32,172		28,924
Income tax expense	3,915		3,407		11,260		10,124
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	7,270		6,325		20,912		18,800
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss/(income) attributable to non-controlling interest	0		0		0		0
Loss on retirement of preferred stock					0
Segment core earnings	7,270		6,325		20,912		18,800
Segment Reporting Information, Additional Information [Abstract]
Assets	5,405,360		5,016,670		5,405,360		5,016,670
On and Off Balance Sheet Program Assets, At Principal Balance	6,725,017		5,951,800		6,725,017		5,951,800
Corporate [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	3,185	[1]	4,683	[2]	9,144	[3]	15,103	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(1,234)	[5]	(910)	[6]	(3,562)	[7]	(3,028)	[8]
Net effective spread	1,951		3,773		5,582		12,075
Guarantee and commitment fees	0		0		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	(619)	[9]	(2,392)	[10]	(1,383)	[11]	(3,566)	[12]
Non-interest (loss)/income	(619)		(2,392)		(1,383)		(3,566)
Release of/(provision for) allowance for loan losses	0		0		0		0
(Release of)/provision for reserve for losses	0		0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(2,986)		(2,626)		(8,975)		(7,797)
Non-interest expense	(2,986)	[13]	(2,626)	[14]	(8,975)	[15]	(7,797)	[16]
Segment core earnings before income taxes	(1,654)		(1,245)		(4,776)		712
Income tax expense	(533)		(2,619)		(3,405)		(19,295)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	(1,121)		1,374		(1,371)		20,007
Preferred Stock Dividends, Income Statement Impact	(3,295)		(3,283)		(9,886)		(6,543)
Less: Net loss/(income) attributable to non-controlling interest	36		(5,412)		(5,199)		(16,778)
Loss on retirement of preferred stock					0
Segment core earnings	(4,380)		(7,321)		(16,456)		(3,314)
Segment Reporting Information, Additional Information [Abstract]
Assets	3,664,107		4,326,791		3,664,107		4,326,791
Segment Reconciling Items [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	(651)	[1]	(962)	[2]	(1,962)	[3]	(13,637)	[4]
Interest Income Reclassification	796		508		2,128		1,552
Total interest expense	1,651	[5]	(14,788)	[6]	5,239	[7]	(18,943)	[8]
Net effective spread	1,796		(15,242)		5,405		(31,028)
Guarantee and commitment fees	(796)		(508)		(2,128)		(1,552)
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	(8,420)	[9]	19,284	[10]	3,927	[11]	15,791	[12]
Non-interest (loss)/income	(9,216)		18,776		1,799		14,239
Release of/(provision for) allowance for loan losses	0		0		0		0
(Release of)/provision for reserve for losses	0		0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	0		0		0		0
Non-interest expense	0	[13]	0	[14]	0	[15]	0	[16]
Segment core earnings before income taxes	(7,420)	[17]	3,534	[18]	7,204	[19]	(16,789)	[20]
Income tax expense	(2,597)		1,237		620		(5,872)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	(4,823)	[17]	2,297	[18]	6,584	[19]	(10,917)	[20]
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss/(income) attributable to non-controlling interest	0		0		0		0
Loss on retirement of preferred stock					(8,147)
Segment core earnings	(4,823)	[17]	2,297	[18]	(1,563)	[19]	(10,917)	[20]
Segment Reporting Information, Additional Information [Abstract]
Assets	0		0		0		0
On and Off Balance Sheet Program Assets, At Principal Balance	$ 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] Includes reconciling adjustments for the amortization of premiums and discounts on assets consolidated at fair value to reflect core earnings amounts.

[4] 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.

[5] 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.

[6] 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.

[7] 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.

[8] 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.

[9] 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.

[10] 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.

[11] 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.

[12] 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.

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

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

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

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

[17] 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

[18] 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.

[19] 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.

[20] 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.