Fair Value Disclosures - Unobservable Input Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended				9 Months Ended				3 Months Ended	9 Months Ended				3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended				9 Months Ended				3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		0 Months Ended		3 Months Ended				9 Months Ended
	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Asset-backed Securities Floating Interest Rate [Member]		Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Sep. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Sep. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3		Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3		Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3		Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3		Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Sep. 30, 2012 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Sep. 30, 2011 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Sep. 30, 2012 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Sep. 30, 2011 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Sep. 30, 2012 Asset-backed Securities Floating Interest Rate [Member]	Dec. 31, 2011 Asset-backed Securities Floating Interest Rate [Member]	Sep. 30, 2012 Asset-backed Securities Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]		Sep. 30, 2011 Asset-backed Securities Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]		Sep. 30, 2012 Asset-backed Securities Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading Securities, Unrealized Gains																						$ 600																																											$ 0	$ 0
Trading Securities, Unrealized Holding Loss																					400		2,000	2,000																																									3,130	3,342
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance, Asset	6,071,067	4,680,327	5,843,186	4,290,443									59,707	60,213	64,335	1,400	[1]	1,430	1,796	1,400					61,137	66,891	62,009	65,735	4,444,467	3,243,965	4,289,272	2,907,264	3,223,332	1,759,205	2,807,627	942,809	29,899	36,530	35,599	37,637	1,191,236	1,448,230	1,446,046	1,926,818	1,418,638	1,120,397	1,279,546	1,005,679	146,825	[2]	249,074	[2]	212,359	[3]	311,765	[4]	1,565,463	1,369,471	1,491,905	1,317,444	59,707	64,682	60,213	64,335			1,430	[5]	2,209	[6]	1,796	[5]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	565,974	1,088,658	1,233,312	2,105,473									0	0	0	0	[1]	0	0	0					0	0	0	0	451,000	1,002,764	856,327	1,804,768	201,000	1,001,500	601,000	1,801,500	0	1,264	5,327	3,268	250,000	0	250,000	0	114,974	85,894	376,985	300,705	0	[2]	0	[2]	0	[3]	0	[4]	114,974	85,894	376,985	300,705	0	0	0	0			0	[5]	0	[6]	0	[5]
Sales, Asset	0	(1,208)	(5,327)	(3,213)									0	0	0	0	[1]	0	0	0					0	0	0	0	0	(1,208)	(5,327)	(3,213)	0	0	0	0	0	(1,208)	(5,327)	(3,213)	0	0	0	0	0	0	0	0	0	[2]	0	[2]	0	[3]	0	[4]	0	0	0	0	0	0	0	0			0	[5]	0	[6]	0	[5]
Settlements, Asset	(344,543)	(53,438)	(784,980)	(705,641)									0	0	0	(686)	[1]	(137)	(664)	(686)					(137)	(136)	(664)	(686)	(252,144)	(2,999)	(504,875)	(481,908)	(1,809)	(2,009)	(2,824)	(2,023)	(335)	(990)	(6,350)	(3,484)	(250,000)	0	(495,701)	(476,401)	(68,516)	(33,179)	(192,309)	(142,965)	(23,746)	[2]	(17,124)	[2]	(87,132)	[3]	(80,082)	[4]	(92,262)	(50,303)	(279,441)	(223,047)	0	0	0	0			(137)	[5]	(136)	[6]	(664)	[5]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	7,937	1,123	5,950	2,749									0	0	0	1,049	[1]	51	212	1,049					51	(310)	212	1,049	8,378	0	8,378	0	8,378	0	8,378	0	0	0	0	0	0	0	0	0	0	0	0	0	(492)	[2]	1,433	[2]	(2,640)	[3]	1,700	[4]	(492)	1,433	(2,640)	1,700	0	0	0	0			51	[5]	(310)	[6]	212	[5]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	78	74,942	8,372	100,593									327	(179)	(2,092)	0	[1]	0	0	0					327	(2,439)	(179)	(2,092)	(3,194)	57,478	4,732	73,089	687	56,771	17,407	73,181	411	1,003	726	2,391	(4,292)	(296)	(13,401)	(2,483)	2,945	19,903	3,819	29,596	0	[2]	0	[2]	0	[3]	0	[4]	2,945	19,903	3,819	29,596	327	(2,439)	(179)	(2,092)			0	[5]	0	[6]	0	[5]
Ending Balance, Asset	6,300,513	5,790,404	6,300,513	5,790,404									60,034	60,034	62,243	1,763	[1]	1,344	1,344	1,763					61,378	64,006	61,378	64,006	4,648,507	4,300,000	4,648,507	4,300,000	3,431,588	2,815,467	3,431,588	2,815,467	29,975	36,599	29,975	36,599	1,186,944	1,447,934	1,186,944	1,447,934	1,468,041	1,193,015	1,468,041	1,193,015	122,587	[2],[3]	233,383	[2],[4]	122,587	[2],[3]	233,383	[2],[4]	1,590,628	1,426,398	1,590,628	1,426,398	60,034	62,243	60,034	62,243			1,344	[5]	1,763	[6]	1,344	[5]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance, Liability	(967)	(1,755)	(1,335)	(3,390)	(967)	[7]	(1,755)	[8]	(1,335)	[7]	(3,390)	[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	0	0	0	0	0	[7]	0	[8]	0	[7]	0	[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales	0	0	0	0	0	[7]	0	[8]	0	[7]	0	[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	0	0	0	0	0	[7]	0	[8]	0	[7]	0	[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	87	(232)	455	1,403	87	[7]	(232)	[8]	455	[7]	1,403	[9]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0	0	0	0	[7]	0	[8]	0	[7]	0	[9]
Ending Balance, Liability	$ (880)	$ (1,987)	$ (880)	$ (1,987)	$ (880)	[7]	$ (1,987)	[8],[9]	$ (880)	[7]	$ (1,987)	[8],[9]

[1] Unrealized gains are attributable to assets still held as of September 30, 2011 and are recorded in Losses on trading assets.

[2] Includes unrealized losses of $0.4 million attributable to assets still held as of September 30, 2012 that are recorded in Losses on trading assets.

[3] Includes unrealized losses of $2.0 million attributable to assets still held as of September 30, 2011 that are recorded in Losses on trading assets.

[4] Includes unrealized losses of $2.0 million attributable to assets still held as of September 30, 2012 that are recorded in Losses on trading assets.

[5] Unrealized gains are attributable to assets still held as of September 30, 2012 and are recorded in Losses on trading assets.

[6] Unrealized losses are attributable to assets still held as of September 30, 2011 and are recorded in Losses on trading assets.

[7] Unrealized gains are attributable to liabilities still held as of September 30, 2012 and are recorded in Gains/(losses) on financial derivatives and hedging activities.

[8] Unrealized losses are attributable to liabilities still held as of September 30, 2011 and are recorded in Gains/(losses) on financial derivatives and hedging activities.

[9] Unrealized gains are attributable to liabilities still held as of September 30, 2011 and are recorded in Gains/(losses) on financial derivatives and hedging activities.