10. STOCKHOLDERS' EQUITY, COMPREHENSIVE INCOME AND STOCK-BASED COMPENSATION (Details 4) - shares	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
RSUs granted	64,000	74,000	35,000
RSUs cancelled	33,000
Stock Option
Available Shares, Beginning	2,169,000	1,847,000	845,000
Additional shares reserved		2,238,000	800,000
Options granted	(338,000)	(368,000)	(92,000)
RSUs granted	(64,000)	(157,000)	(35,000)
Options terminated	16,000	55,000	329,000
Plan shares expired	(4,000)	(1,446,000)
Available Shares, Ending	1,812,000	2,169,000	1,847,000