Fair Value Disclosures - Unobservable Input Reconciliation (Details) (Fair Value, Inputs, Level 3 [Member], Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 5,176,636		$ 6,742,583		$ 6,770,031		$ 6,421,447
Purchases	392,975		423,872		1,017,519		1,282,189
Sales	14,550		0		26,675		0
Settlements	428,864		318,058		1,094,797		779,645
Realized and Unrealized Gains/(Losses) included in Income	(3,031)		2,370		3,745		(15,615)
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	6,192		(16,722)		71,621		(74,331)
Transfers Out					1,612,086
Ending Balance	5,129,358		6,834,045		5,129,358		6,834,045
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance			390		235		691
Purchases			0		0		0
Sales			0		0		0
Settlements			0		0		0
Realized and Unrealized Gains/(Losses) included in Income			61		235		362
Unrealized Gains/(Losses) included in Other Comprehen-sive Income			0		0		0
Transfers Out					0
Ending Balance	0		329		0		329
Investment Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	56,051		66,374		66,418		64,406
Purchases	0		0		0		233
Sales	14,550		0		26,675		0
Settlements	134		164		559		673
Realized and Unrealized Gains/(Losses) included in Income	(426)		69		(435)		386
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	797		0		2,989		1,927
Transfers Out					0
Ending Balance	41,738		66,279		41,738		66,279
Farmer Mac Guaranteed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchases	295,700
USDA Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading Securities, Unrealized Holding Loss	0		400				500
Trading Securities, Unrealized Gains					700
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,683,029		1,617,356		1,612,013		1,590,783
Purchases	97,275		70,372		256,044		303,456
Sales	0		0		0		0
Settlements	45,900		58,958		178,458		234,686
Realized and Unrealized Gains/(Losses) included in Income	(56)		(695)		161		(1,129)
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	(3,503)		935		41,085		(29,414)
Transfers Out					0
Ending Balance	1,730,845		1,629,010		1,730,845		1,629,010
Available-for-sale Securities [Member] | Investment Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	55,171		65,310		65,490		63,159
Purchases	0		0		0		233
Sales	14,550		0		26,675		0
Settlements	7		8		18		17
Realized and Unrealized Gains/(Losses) included in Income	(450)		0		(825)		0
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	797		0		2,989		1,927
Transfers Out					0
Ending Balance	40,961		65,302		40,961		65,302
Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,437,556		5,058,853		5,091,600		4,766,258
Purchases			353,500		761,475		978,500
Sales	0		0		0		0
Settlements	382,830		258,936		915,780		544,286
Realized and Unrealized Gains/(Losses) included in Income	(2,549)		2,996		4,019		(14,872)
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	8,898		(17,657)		27,547		(46,844)
Transfers Out					1,612,086
Ending Balance	3,356,775		5,138,756		3,356,775		5,138,756
Available-for-sale Securities [Member] | USDA Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,636,930		1,543,764		1,553,669		1,486,595
Purchases	97,275		70,372		256,044		303,456
Sales	0		0		0		0
Settlements	42,821		48,380		162,917		193,946
Realized and Unrealized Gains/(Losses) included in Income	0		0		0		0
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	(3,503)		935		41,085		(29,414)
Transfers Out					0
Ending Balance	1,687,881		1,566,691		1,687,881		1,566,691
Trading Securities [Member] | Investment Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	880		1,064		928		1,247
Purchases	0		0		0		0
Sales	0		0		0		0
Settlements	127		156		541		656
Realized and Unrealized Gains/(Losses) included in Income	24		69		390		386
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	0		0		0		0
Transfers Out					0
Ending Balance	777		977		777		977
Trading Securities [Member] | USDA Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	46,099	[1]	73,592	[2]	58,344	[1]	104,188	[2]
Purchases	0	[1]	0	[2]	0	[1]	0	[2]
Sales	0	[1]	0	[2]	0	[1]	0	[2]
Settlements	3,079	[1]	10,578	[2]	15,541	[1]	40,740	[2]
Realized and Unrealized Gains/(Losses) included in Income	(56)	[1]	(695)	[2]	161	[1]	(1,129)	[2]
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	0	[1]	0	[2]	0	[1]	0	[2]
Transfers Out					0
Ending Balance	42,964	[1]	62,319	[2]	42,964	[1]	62,319	[2]
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Floating rate auction-rate certificates backed by Government guaranteed student loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	54,976		65,088		65,285		63,159
Purchases	0		0		0		0
Sales	14,550		0		26,675		0
Settlements	0		0		0		0
Realized and Unrealized Gains/(Losses) included in Income	(450)		0		(825)		0
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	798		0		2,989		1,929
Transfers Out					0
Ending Balance	40,774		65,088		40,774		65,088
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	195		222		205		0
Purchases	0		0		0		233
Sales	0		0		0		0
Settlements	7		8		18		17
Realized and Unrealized Gains/(Losses) included in Income	0		0		0		0
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	(1)		0		0		(2)
Transfers Out					0
Ending Balance	187		214		187		214
Floating Interest Rate [Member] | Trading Securities [Member] | Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	880	[3]	1,064	[4]	928	[3]	1,247	[4]
Purchases	0	[3]	0	[4]	0	[3]	0	[4]
Sales	0	[3]	0	[4]	0	[3]	0	[4]
Settlements	127	[3]	156	[4]	541	[3]	656	[4]
Realized and Unrealized Gains/(Losses) included in Income	24	[3]	69	[4]	390	[3]	386	[4]
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	0	[3]	0	[4]	0	[3]	0	[4]
Transfers Out					0
Ending Balance	777	[3]	977	[4]	777	[3]	977	[4]
Institutional Credit [Member] | Farmer Mac Guaranteed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchases	295,700
Institutional Credit [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,416,512		5,033,059		5,070,366		4,739,577
Purchases			353,500		761,475		978,500
Sales	0		0		0		0
Settlements	382,630		258,522		915,218		542,974
Realized and Unrealized Gains/(Losses) included in Income	(2,549)		2,996		4,019		(14,872)
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	9,293		(17,985)		27,770		(47,183)
Transfers Out					1,612,086
Ending Balance	3,336,326		5,113,048		3,336,326		5,113,048
USDA Guarantees [Member] | Farmer Mac Guaranteed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchases	0
USDA Guarantees [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	21,044		25,794		21,234		26,681
Purchases			0		0		0
Sales	0		0		0		0
Settlements	200		414		562		1,312
Realized and Unrealized Gains/(Losses) included in Income	0		0		0		0
Unrealized Gains/(Losses) included in Other Comprehen-sive Income	(395)		328		(223)		339
Transfers Out					0
Ending Balance	20,449		25,708		20,449		25,708
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance			390	[5]	235	[6]	691	[5]
Purchases			0	[5]	0	[6]	0	[5]
Sales			0	[5]	0	[6]	0	[5]
Settlements			0	[5]	0	[6]	0	[5]
Realized and Unrealized Gains/(Losses) included in Income			61	[5]	235	[6]	362	[5]
Unrealized Gains/(Losses) included in Other Comprehen-sive Income			0	[5]	0	[6]	0	[5]
Transfers Out					0
Ending Balance	$ 0	[6]	$ 329	[5]	$ 0	[6]	$ 329	[5]

[1] Includes immaterial unrealized gains attributable to assets still held as of September 30, 2014 that are recorded in "Gains/(losses) on trading securities."

[2] Includes unrealized losses of $0.4 million attributable to assets still held as of September 30, 2013 that are recorded in "Gains/(losses) on trading securities."

[3] Unrealized gains are attributable to assets still held as of September 30, 2014 and are recorded in "Gains/(losses) on trading securities."

[4] Unrealized gains are attributable to assets still held as of September 30, 2013 and are recorded in "Gains/(losses) on trading securities."

[5] Unrealized gains are attributable to liabilities still held as of September 30, 2013 and are recorded in "Gains/(losses) on financial derivatives and hedging activities."

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