Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Aug. 31, 2015	May. 31, 2015
Receivables, allowance	$ 3,475	$ 2,775
Intangible assets, accumulated amortization	$ 17,961	$ 15,957
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.30	$ 0.30
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	21,653,985	20,909,402
Treasury stock at cost, shares	546,977	546,977