Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Feb. 28, 2014		Feb. 28, 2013	Feb. 28, 2014		Feb. 28, 2013	Nov. 30, 2013	May 31, 2013		Nov. 30, 2012	May 31, 2012
Statement of operations:
Interest income	$ 238,732		$ 234,021	$ 719,057		$ 715,736
Interest expense	(163,534)		(171,899)	(496,464)		(522,796)
Net interest income	75,198		62,122	222,593		192,940
Provision for loan losses	(787)		378	(3,161)		(4,927)
Net interest income after provision for loan losses	74,411		62,500	219,432		188,013
Non-interest income:
Fee and other income	5,702		6,337	14,983		29,102
Derivative (gains) losses	(31,623)		46,626	43,981		18,268
Results of operations of foreclosed assets	(1,164)		6,478	(8,482)		804
Total non-interest income	(27,085)		59,441	50,482		48,174
Non-interest expense:
General and administrative expenses	(17,183)		(30,279)	(54,371)		(66,900)
Provision for (recovery of) guarantee liability	(117)		46	(159)		147
Losses on early extinguishment of debt	(1,452)		0	(1,452)		0
Other	210		(554)	(88)		(5,101)
Total non-interest expense	(18,542)		(30,787)	(56,070)		(71,854)
Income prior to income taxes	28,784		91,154	213,844		164,333
Income tax expense	(243)		(1,067)	(2,045)		(1,519)
Net income	28,541		90,087	211,799		162,814
Assets:
Total loans outstanding	20,635,333	[1],[2]	19,477,734	20,635,333	[1],[2]	19,477,734		20,296,317	[1],[2]
Deferred origination costs	9,731		8,414	9,731		8,414		9,557
Less: Allowance for loan losses	(56,040)		(148,411)	(56,040)		(148,411)	(55,199)	(54,325)		(148,737)	(143,326)
Loans to members, net	20,589,024		19,337,737	20,589,024		19,337,737		20,251,549
Other assets	2,518,305		2,160,464	2,518,305		2,160,464
Total assets	23,107,329		21,498,201	23,107,329		21,498,201		22,071,651
Other
Statement of operations:
Interest income	12,613		13,971	37,958		42,304
Interest expense	(9,185)		(10,395)	(27,766)		(31,558)
Net interest income	3,428		3,576	10,192		10,746
Provision for loan losses	0		0	0		0
Net interest income after provision for loan losses	3,428		3,576	10,192		10,746
Non-interest income:
Fee and other income	374		335	1,068		1,021
Derivative (gains) losses	(815)		1,690	438		(232)
Results of operations of foreclosed assets	0		0	0		0
Total non-interest income	(441)		2,025	1,506		789
Non-interest expense:
General and administrative expenses	(2,505)		(2,870)	(6,630)		(7,648)
Provision for (recovery of) guarantee liability	0		0	0		0
Losses on early extinguishment of debt	0			0
Other	0		0	1		0
Total non-interest expense	(2,505)		(2,870)	(6,629)		(7,648)
Income prior to income taxes	482		2,731	5,069		3,887
Income tax expense	(243)		(1,067)	(2,045)		(1,519)
Net income	239		1,664	3,024		2,368
Assets:
Total loans outstanding	1,234,787		1,245,392	1,234,787		1,245,392
Deferred origination costs	0		0	0		0
Less: Allowance for loan losses	0		0	0		0
Loans to members, net	1,234,787		1,245,392	1,234,787		1,245,392
Other assets	145,847		151,832	145,847		151,832
Total assets	1,380,634		1,397,224	1,380,634		1,397,224
Elimination
Statement of operations:
Interest income	(8,808)		(9,989)	(26,659)		(30,289)
Interest expense	8,808		9,987	26,659		30,287
Net interest income	0		(2)	0		(2)
Provision for loan losses	0		0	0		0
Net interest income after provision for loan losses	0		(2)	0		(2)
Non-interest income:
Fee and other income	201		(227)	601		(681)
Derivative (gains) losses	0		(18)	0		(18)
Results of operations of foreclosed assets	0		0	0		0
Total non-interest income	201		(245)	601		(699)
Non-interest expense:
General and administrative expenses	(201)		229	(601)		683
Provision for (recovery of) guarantee liability	0		0	0		0
Losses on early extinguishment of debt	0			0
Other	0		18	0		18
Total non-interest expense	(201)		247	(601)		701
Income prior to income taxes	0		0	0		0
Income tax expense	0		0	0		0
Net income	0		0	0		0
Assets:
Total loans outstanding	(1,204,808)		(1,213,018)	(1,204,808)		(1,213,018)
Deferred origination costs	0		0	0		0
Less: Allowance for loan losses	0		0	0		0
Loans to members, net	(1,204,808)		(1,213,018)	(1,204,808)		(1,213,018)
Other assets	(120,199)		(124,793)	(120,199)		(124,793)
Total assets	(1,325,007)		(1,337,811)	(1,325,007)		(1,337,811)
CFC
Statement of operations:
Interest income	234,927		230,039	707,758		703,721
Interest expense	(163,157)		(171,491)	(495,357)		(521,525)
Net interest income	71,770		58,548	212,401		182,196
Provision for loan losses	(787)		378	(3,161)		(4,927)
Net interest income after provision for loan losses	70,983		58,926	209,240		177,269
Non-interest income:
Fee and other income	5,127		6,229	13,314		28,762
Derivative (gains) losses	(30,808)		44,954	43,543		18,518
Results of operations of foreclosed assets	(1,164)		6,478	(8,482)		804
Total non-interest income	(26,845)		57,661	48,375		48,084
Non-interest expense:
General and administrative expenses	(14,477)		(27,638)	(47,140)		(59,935)
Provision for (recovery of) guarantee liability	(117)		46	(159)		147
Losses on early extinguishment of debt	(1,452)			(1,452)
Other	210		(572)	(89)		(5,119)
Total non-interest expense	(15,836)		(28,164)	(48,840)		(64,907)
Income prior to income taxes	28,302		88,423	208,775		160,446
Income tax expense	0		0	0		0
Net income	28,302		88,423	208,775		160,446
Assets:
Total loans outstanding	19,400,546	[1],[2]	19,445,360	19,400,546	[1],[2]	19,445,360		19,019,817	[1],[2]
Deferred origination costs	9,731		8,414	9,731		8,414
Less: Allowance for loan losses	(44,359)		(134,062)	(44,359)		(134,062)	(42,762)	(41,246)		(133,578)	(126,941)
Loans to members, net	20,559,045		19,305,363	20,559,045		19,305,363
Other assets	2,492,657		2,133,425	2,492,657		2,133,425
Total assets	$ 23,051,702		$ 21,438,788	$ 23,051,702		$ 21,438,788

[1] Excludes deferred origination costs of $10 million at February 28, 2014 and May 31, 2013.

[2] Includes nonperforming and restructured loans.