Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	Feb. 29, 2016	May. 31, 2015
Assets:
Earn-Out Payments	$ 346	$ 376
Total assets at fair value	346	376
Assets:
Earn-Out Payments	0
Total assets at fair value	0
Assets:
Earn-Out Payments	0
Total assets at fair value	0
Assets:
Earn-Out Payments	346	376
Total assets at fair value	$ 346	$ 376