Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	May 31, 2018	May 31, 2017
Statement Of Financial Position [Abstract]
Receivables, allowances	$ 632	$ 3,444
Other intangible assets, accumulated amortization	$ 74,922	$ 63,134
Preferred shares, without par value
Preferred shares, shares authorized	1,000,000	1,000,000
Preferred shares, shares issued	0	0
Preferred shares, shares outstanding	0	0
Common stock, without par value
Common shares, authorized	150,000,000	150,000,000
Common shares, shares issued	58,876,921	62,802,456
Common shares, shares outstanding	58,876,921	62,802,456
Accumulated other comprehensive income (loss), taxes	$ 2,908	$ 5,310