Fair Value Disclosures - Unobservable Input Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended				6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended				6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended				6 Months Ended				3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		0 Months Ended		3 Months Ended				6 Months Ended
	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Derivative Financial Instruments, Liabilities [Member]		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Available-for-sale Securities [Member]	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Asset-backed Securities Floating Interest Rate [Member]		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Trading Account Assets [Member]	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3 Investment Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac I Guaranteed Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac II Guaranteed Securities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Jun. 30, 2012 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Jun. 30, 2011 Farmer Mac Guarantee Fair Value, Measurements, Recurring [Member] Level 3 Farmer Mac Guaranteed Securities - Rural Utilities	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2011 Fair Value, Measurements, Recurring [Member] Level 3	Jun. 30, 2012 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Jun. 30, 2011 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Jun. 30, 2012 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Jun. 30, 2011 Auction-rate certificates backed by Government guaranteed student loans Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]	Jun. 30, 2012 Asset-backed Securities Floating Interest Rate [Member]	Dec. 31, 2011 Asset-backed Securities Floating Interest Rate [Member]	Jun. 30, 2012 Asset-backed Securities Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]		Jun. 30, 2011 Asset-backed Securities Fair Value, Measurements, Recurring [Member] Level 3 Floating Interest Rate [Member]		Jun. 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																									$ 300	[1]																																													$ 0	$ 0
Trading Securities, Unrealized Holding Loss																							2,400	[1]			1,600	[1]	2,400	[1]																																									3,181	3,342
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance, Asset	5,963,474	4,314,244	5,843,186	4,290,443									58,868	64,539	60,213	64,335	1,400	[2]	1,646	1,690	1,796	1,400									60,514	66,229	62,009	65,735	4,389,861	2,909,914	4,289,272	2,907,264	3,008,223	1,429,318	2,807,627	942,809	36,129	37,803	35,599	37,637	1,345,509	1,442,793	1,446,046	1,926,818	1,328,702	1,063,540	1,279,546	1,005,679	184,397	[3]	274,561	[3]	212,359	[3]	311,765	[3]	1,513,099	1,338,101	1,491,905	1,317,444	58,868	64,539	60,213	64,335			1,646	[4]	1,690	[2]	1,796	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	365,613	399,445	667,338	1,016,815									0	0	0	0	0	[2]	0	0	0	0									0	0	0	0	205,327	300,981	405,327	802,004	200,000	300,000	400,000	800,000	5,327	981	5,327	2,004	0	0	0	0	160,286	98,464	262,011	214,811	0	[3]	0	[3]	0	[3]	0	[3]	160,286	98,464	262,011	214,811	0	0	0	0			0	[4]	0	[2]	0	[2]
Sales, Asset	(5,327)	(1,041)	(5,327)	(2,005)									0	0	0	0	0	[2]	0	0	0	0									0	0	0	0	(5,327)	(1,041)	(5,327)	(2,005)	0	0	0	0	(5,327)	(1,041)	(5,327)	(2,005)	0	0	0	0	0	0	0	0	0	[3]	0	[3]	0	[3]	0	[3]	0	0	0	0	0	0	0	0			0	[4]	0	[2]	0	[2]
Settlements, Asset	(261,271)	(77,244)	(440,437)	(652,203)									0	0	0	0	(550)	[2]	(239)	(168)	(527)	(550)									(239)	(168)	(527)	(550)	(156,794)	(1,140)	(252,731)	(478,909)	(1,007)	(6)	(1,015)	(14)	(5,787)	(1,134)	(6,015)	(2,494)	(150,000)	0	(245,701)	(476,401)	(69,775)	(48,951)	(123,793)	(109,786)	(34,463)	[3]	(26,985)	[3]	(63,386)	[3]	(62,958)	[3]	(104,238)	(75,936)	(187,179)	(172,744)	0	0	0	0			(239)	[4]	(168)	[2]	(527)	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(3,086)	2,185	(1,987)	1,626									0	0	0	0	1,359	[2]	23	687	161	1,359									23	687	161	1,359	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	(3,109)	[3]	1,498	[3]	(2,148)	[3]	267	[3]	(3,109)	1,498	(2,148)	267	0	0	0	0			23	[4]	687	[2]	161	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	11,664	42,738	8,294	25,651									839	143	(506)	347	0	[2]	0	0	0	0									839	143	(506)	347	11,400	35,251	7,926	15,611	16,116	29,893	16,720	16,410	(443)	(79)	315	1,388	(4,273)	5,437	(9,109)	(2,187)	(575)	7,344	874	9,693	0	[3]	0	[3]	0	[3]	0	[3]	(575)	7,344	874	9,693	839	143	(506)	347			0	[4]	0	[2]	0	[2]
Ending Balance, Asset	6,071,067	4,680,327	6,071,067	4,680,327									59,707	64,682	59,707	64,682	2,209		1,430	2,209	1,430	2,209									61,137	66,891	61,137	66,891	4,444,467	3,243,965	4,444,467	3,243,965	3,223,332	1,759,205	3,223,332	1,759,205	29,899	36,530	29,899	36,530	1,191,236	1,448,230	1,191,236	1,448,230	1,418,638	1,120,397	1,418,638	1,120,397	146,825	[3]	249,074	[3]	146,825	[3]	249,074	[3]	1,565,463	1,369,471	1,565,463	1,369,471	59,707	64,682	59,707	64,682			1,430	[2],[4]	2,209	[2]	1,430	[2],[4]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance, Liability	(1,225)	(1,671)	(1,335)	(3,390)	(1,225)	[5]	(1,671)	[6]	(1,335)	[5]	(3,390)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	0	0	0	0	0	[5]	0	[6]	0	[5]	0	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales	0	0	0	0	0	[5]	0	[6]	0	[5]	0	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	0	0	0	0	0	[5]	0	[6]	0	[5]	0	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	258	(84)	368	1,635	258	[5]	(84)	[6]	368	[5]	1,635	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0	0	0	0	[5]	0	[6]	0	[5]	0	[6]
Ending Balance, Liability	$ (967)	$ (1,755)	$ (967)	$ (1,755)	$ (967)	[5]	$ (1,755)	[6]	$ (967)	[5]	$ (1,755)	[6]

[1] Includes unrealized losses of $2.4 million attributable to assets still held as of June 30, 2011 that are recorded in (Losses)/gains on trading assets.

[2] Unrealized gains are attributable to assets still held as of June 30, 2011 and are recorded in (Losses)/gains on trading assets.

[3] Includes unrealized losses of $2.4 million attributable to assets still held as of June 30, 2012 that are recorded in (Losses)/gains on trading assets.

[4] Unrealized gains are attributable to assets still held as of June 30, 2012 and are recorded in (Losses)/gains on trading assets.

[5] Unrealized gains are attributable to liabilities still held as of June 30, 2012 and are recorded in Losses on financial derivatives.

[6] Unrealized losses are attributable to liabilities still held as of June 30, 2011 and are recorded in Losses on financial derivatives.