General Information and Accounting Policies (Details 3) (USD $)	3 Months Ended
	Aug. 31, 2013	Aug. 31, 2012	May 31, 2013
Components of interest income
Interest on investments	$ 1,936,000	$ 938,000
Fee income	2,016,000	2,028,000
Total interest income	241,071,000	240,085,000
Deferred conversion fees	37,000,000		21,000,000
Long-term fixed-rate loans
Components of interest income
Total interest income	224,583,000	217,940,000
Long-term variable-rate loans
Components of interest income
Total interest income	4,828,000	6,025,000
Line of credit loans
Components of interest income
Total interest income	7,572,000	7,692,000
Restructured loans
Components of interest income
Total interest income	$ 136,000	$ 5,462,000