Loans and Commitments (Details 8) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014		May 31, 2014		Aug. 31, 2013
Loan Security
Total loans outstanding	$ 20,474,871	[1],[2]	$ 20,466,925	[1],[2]	$ 20,405,091
Loans receivable as a percentage of total loan (percent)	100.00%		100.00%
CFC
Loan Security
Total loans outstanding	19,399,517	[1]	19,189,430	[1]
RTFC
Loan Security
Total loans outstanding	436,852	[1]	449,546	[1]
NCSC
Loan Security
Total loans outstanding	638,502	[1]	827,949	[1]
Secured
Loan Security
Total loans outstanding	18,275,480		18,348,633
Loans receivable as a percentage of total loan (percent)	89.00%		90.00%
Secured | CFC
Loan Security
Total loans outstanding	17,437,542		17,313,990
Loans receivable as a percentage of total loan (percent)	90.00%		90.00%
Secured | RTFC
Loan Security
Total loans outstanding	419,694		429,626
Loans receivable as a percentage of total loan (percent)	96.00%		96.00%
Secured | NCSC
Loan Security
Total loans outstanding	418,244		605,017
Loans receivable as a percentage of total loan (percent)	66.00%		73.00%
Unsecured
Loan Security
Total loans outstanding	2,199,391		2,118,292
Loans receivable as a percentage of total loan (percent)	11.00%		10.00%
Unsecured | CFC
Loan Security
Total loans outstanding	1,961,975		1,875,440
Loans receivable as a percentage of total loan (percent)	10.00%		10.00%
Unsecured | RTFC
Loan Security
Total loans outstanding	17,158		19,920
Loans receivable as a percentage of total loan (percent)	4.00%		4.00%
Unsecured | NCSC
Loan Security
Total loans outstanding	220,258		222,932
Loans receivable as a percentage of total loan (percent)	34.00%		27.00%
Long-term fixed-rate loans
Loan Security
Total loans outstanding	18,353,930	[1]	18,175,656	[1]
Long-term fixed-rate loans | Secured
Loan Security
Total loans outstanding	17,335,025		17,185,456
Loans receivable as a percentage of total loan (percent)	94.00%		95.00%
Long-term fixed-rate loans | Unsecured
Loan Security
Total loans outstanding	1,018,905		990,200
Loans receivable as a percentage of total loan (percent)	6.00%		5.00%
Long-term variable-rate loans
Loan Security
Total loans outstanding	684,141	[1]	753,918	[1]
Long-term variable-rate loans | Secured
Loan Security
Total loans outstanding	597,893		650,211
Loans receivable as a percentage of total loan (percent)	87.00%		86.00%
Long-term variable-rate loans | Unsecured
Loan Security
Total loans outstanding	86,248		103,707
Loans receivable as a percentage of total loan (percent)	13.00%		14.00%
Loans guaranteed by RUS
Loan Security
Total loans outstanding	200,535	[1]	201,863	[1]
Loans guaranteed by RUS | Secured
Loan Security
Total loans outstanding	200,535		201,863
Loans receivable as a percentage of total loan (percent)	100.00%		100.00%
Line of credit loans
Loan Security
Total loans outstanding	1,236,265	[1]	1,335,488	[1]
Line of credit loans | Secured
Loan Security
Total loans outstanding	142,027		311,103
Loans receivable as a percentage of total loan (percent)	11.00%		23.00%
Line of credit loans | Unsecured
Loan Security
Total loans outstanding	$ 1,094,238		$ 1,024,385
Loans receivable as a percentage of total loan (percent)	89.00%		77.00%

[1] Includes nonperforming and restructured loans.

[2] Includes the unpaid principal balance excluding deferred loan origination costs.