Fair Value Measurement (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	$ 2,313	$ (479)	$ (2,931)	$ 408