Quarterly Information - Quarterly Information (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales	$ 86,914	$ 85,602	$ 89,029	$ 88,098	$ 93,419	$ 87,434	$ 89,284	$ 83,753	$ 349,643	$ 353,890	$ 356,534
Gross profit	42,335	43,792	45,010	45,032	41,527	43,534	45,884	43,371	176,169	174,316	175,796
Net income (loss)	(12,913)	$ 2,887	$ 13,734	$ 1,300	$ (43,075)	$ 594	$ (334)	$ (775)	$ 5,008	(43,590)	$ (3,388)
Deferred Tax Assets, Valuation Allowance										$ 40,400
Discontinued Operations, Disposed of by Means Other than Sale | Acculis Capital Systems
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, impact to income	$ 4,500