Guarantees (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Activity in the guarantee liability account
Beginning balance as of May 31, 2013			$ 24,742
Net change in non-contingent liability	(1,729)		(1,729)
Provision for contingent guarantee liability	117	(46)	159	(147)
Ending balance as of February 28, 2014	$ 23,172		$ 23,172
Liability as a percentage of total guarantees	2.09%		2.09%