Business Segment Reporting - Core Earnings - Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	$ 66,392	[1]	$ 64,475	[2]	$ 130,343	[3]	$ 116,927	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(34,528)	[5]	(42,502)	[6]	(67,690)	[7]	(77,228)	[8]
Net effective spread	31,864		21,973		62,653		39,699
Guarantee and commitment fees	3,388		3,703		6,765		7,487
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	14,819	[9]	2,561	[10]	11,917	[11]	(4,258)	[12]
Non-interest income/(loss)	18,207		6,264		18,682		3,229
(Provision for)/release of allowance for loan losses	(110)		1,583		(186)		1,010
(Release of)/provision for reserve for losses	(1,146)		974		(374)		873
Noninterest Expense, Excluding Loan, Lease and Other Losses	(9,707)		(8,830)		(18,822)		(16,676)
Noninterest Expense	(10,853)	[13]	(7,856)	[14]	(19,196)	[15]	(15,803)	[16]
Income before income taxes	39,108		21,964		61,953		28,135
Income tax expense	(13,769)		6,368		(18,000)		7,509
Net income	25,339		28,332		43,953		35,644
Preferred Stock Dividends, Income Statement Impact	(3,296)		(2,308)		(6,591)		(3,260)
Less: Net loss/(income) attributable to non-controlling interest	119		(5,819)		(5,235)		(11,366)
Loss on retirement of preferred stock	0		0		(8,147)		0
Net income attributable to common stockholders	22,162		20,205		23,980		21,018
Segment Reporting Information, Additional Information [Abstract]
Assets	15,144,597		14,670,102		15,144,597		14,670,102		$ 14,287,821
On and Off Balance Sheet Program Assets, At Principal Balance	15,130,127		14,072,542		15,130,127		14,072,542
Farm & Ranch [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	22,159	[1]	19,598	[2]	44,127	[3]	37,936	[4]
Interest Income Reclassification	(697)		(513)		(1,332)		(1,044)
Total interest expense	(11,781)	[5]	(11,265)	[6]	(23,000)	[7]	(21,958)	[8]
Net effective spread	9,681		7,820		19,795		14,934
Guarantee and commitment fees	3,693		3,807		7,326		7,716
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	160	[9]	242	[10]	247	[11]	373	[12]
Non-interest income/(loss)	3,853		4,049		7,573		8,089
(Provision for)/release of allowance for loan losses	(110)		1,583		(186)		1,010
(Release of)/provision for reserve for losses	(1,146)		974		(374)		873
Noninterest Expense, Excluding Loan, Lease and Other Losses	(4,304)		(3,914)		(8,630)		(7,466)
Noninterest Expense	(5,450)	[13]	(2,940)	[14]	(9,004)	[15]	(6,593)	[16]
Segment core earnings before income taxes	7,974		10,512		18,178		17,440
Income tax expense	(2,791)		(3,679)		(6,362)		(6,103)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	5,183		6,833		11,816		11,337
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	5,183		6,833		11,816		11,337
Segment Reporting Information, Additional Information [Abstract]
Assets	2,780,018		2,387,899		2,780,018		2,387,899
On and Off Balance Sheet Program Assets, At Principal Balance	5,485,570		5,310,664		5,485,570		5,310,664
USDA Guarantees [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	14,779	[1]	13,307	[2]	29,127	[3]	26,266	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(10,313)	[5]	(9,148)	[6]	(20,436)	[7]	(18,323)	[8]
Net effective spread	4,466		4,159		8,691		7,943
Guarantee and commitment fees	8		23		2		49
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	28	[9]	9	[10]	87	[11]	36	[12]
Non-interest income/(loss)	36		32		89		85
(Provision for)/release of 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	(1,025)		(764)		(1,410)		(1,495)
Noninterest Expense	(1,025)	[13]	(764)	[14]	(1,410)	[15]	(1,495)	[16]
Segment core earnings before income taxes	3,477		3,427		7,370		6,533
Income tax expense	(1,216)		(1,200)		(2,579)		(2,288)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	2,261		2,227		4,791		4,245
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	2,261		2,227		4,791		4,245
Segment Reporting Information, Additional Information [Abstract]
Assets	1,913,390		1,721,003		1,913,390		1,721,003
On and Off Balance Sheet Program Assets, At Principal Balance	1,862,430		1,710,335		1,862,430		1,710,335
Rural Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	6,521	[1]	6,782	[2]	13,106	[3]	14,525	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(3,683)	[5]	(3,829)	[6]	(7,464)	[7]	(9,582)	[8]
Net effective spread	2,838		2,953		5,642		4,943
Guarantee and commitment fees	0		0		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	0	[9]	0	[10]	0	[11]	0	[12]
Non-interest income/(loss)	0		0		0		0
(Provision for)/release of 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	(860)		(830)		(1,726)		(1,607)
Noninterest Expense	(860)	[13]	(830)	[14]	(1,726)	[15]	(1,607)	[16]
Segment core earnings before income taxes	1,978		2,123		3,916		3,336
Income tax expense	(691)		(743)		(1,369)		(1,168)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	1,287		1,380		2,547		2,168
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	1,287		1,380		2,547		2,168
Segment Reporting Information, Additional Information [Abstract]
Assets	962,702		1,022,421		962,702		1,022,421
On and Off Balance Sheet Program Assets, At Principal Balance	954,188		1,012,313		954,188		1,012,313
Institutional Credit [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	20,036	[1]	20,073	[2]	39,335	[3]	40,455	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(9,176)	[5]	(10,116)	[6]	(18,050)	[7]	(21,092)	[8]
Net effective spread	10,860		9,957		21,285		19,363
Guarantee and commitment fees	384		386		769		766
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	0	[9]	0	[10]	0	[11]	0	[12]
Non-interest income/(loss)	384		386		769		766
(Provision for)/release of 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	(532)		(492)		(1,067)		(937)
Noninterest Expense	(532)	[13]	(492)	[14]	(1,067)	[15]	(937)	[16]
Segment core earnings before income taxes	10,712		9,851		20,987		19,192
Income tax expense	(3,749)		(3,447)		(7,345)		(6,717)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	6,963		6,404		13,642		12,475
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	6,963		6,404		13,642		12,475
Segment Reporting Information, Additional Information [Abstract]
Assets	5,874,088		5,115,147		5,874,088		5,115,147
On and Off Balance Sheet Program Assets, At Principal Balance	6,827,939		6,039,230		6,827,939		6,039,230
Corporate [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	3,094	[1]	5,185	[2]	5,959	[3]	10,420	[4]
Interest Income Reclassification	0		0		0		0
Total interest expense	(1,152)	[5]	(1,025)	[6]	(2,328)	[7]	(2,118)	[8]
Net effective spread	1,942		4,160		3,631		8,302
Guarantee and commitment fees	0		0		0		0
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	(212)	[9]	(603)	[10]	(764)	[11]	(1,174)	[12]
Non-interest income/(loss)	(212)		(603)		(764)		(1,174)
(Provision for)/release of 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)		(2,830)		(5,989)		(5,171)
Noninterest Expense	(2,986)	[13]	(2,830)	[14]	(5,989)	[15]	(5,171)	[16]
Segment core earnings before income taxes	(1,256)		727		(3,122)		1,957
Income tax expense	356		13,803		2,872		16,676
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	(900)		14,530		(250)		18,633
Preferred Stock Dividends, Income Statement Impact	(3,296)		(2,308)		(6,591)		(3,260)
Less: Net loss/(income) attributable to non-controlling interest	119		(5,819)		(5,235)		(11,366)
Loss on retirement of preferred stock					0
Segment core earnings	(4,077)		6,403		(12,076)		4,007
Segment Reporting Information, Additional Information [Abstract]
Assets	3,614,399		4,423,632		3,614,399		4,423,632
Segment Reconciling Items [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Interest and Dividend Income, Operating	(197)	[1]	(470)	[2]	(1,311)	[3]	(12,675)	[4]
Interest Income Reclassification	697		513		1,332		1,044
Total interest expense	1,577	[5]	(7,119)	[6]	3,588	[7]	(4,155)	[8]
Net effective spread	2,077		(7,076)		3,609		(15,786)
Guarantee and commitment fees	(697)		(513)		(1,332)		(1,044)
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	14,843	[9]	2,913	[10]	12,347	[11]	(3,493)	[12]
Non-interest income/(loss)	14,146		2,400		11,015		(4,537)
(Provision for)/release of 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
Noninterest Expense	0	[13]	0	[14]	0	[15]	0	[16]
Segment core earnings before income taxes	16,223	[17]	(4,676)	[18]	14,624	[19]	(20,323)	[20]
Income tax expense	(5,678)		1,634		(3,217)		7,109
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	10,545	[17]	(3,042)	[18]	11,407	[19]	(13,214)	[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	10,545	[17]	(3,042)	[18]	3,260	[19]	(13,214)	[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 "Gains/(losses) 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 "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.

[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 "Gains/(losses) 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 "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.

[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.