Assets and liabilities measured at fair value on a recurring basis (Details) ( in Thousands) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2015	May. 31, 2015
Total:
Earn-Out Payments	$ 386	$ 376
Total assets at fair value	386	376
Quoted prices in active markets (Level 1)
Earn-Out Payments	0	0
Total assets at fair value	0	0
Significant other observable inputs (Level 2)
Earn-Out Payments	0	0
Total assets at fair value	0	0
Significant unobservable inputs (Level 3)
Earn-Out Payments	386	376
Total assets at fair value	$ 386	$ 376