Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Effect to the participating securities as result of net loss			$ 0.0
Basic and Diluted EPS:
Income (Loss) from continuing operations	$ (22.5)	$ 12.1	(11.9)	$ 22.0
Less income attributable to participating shares		(0.1)		(0.2)
Income (Loss) from continuing operations attributable to common shareholders	(22.5)	12.0	(11.9)	21.8
Income (Loss) from discontinued operations attributable to common shareholders	(0.1)		(0.1)	(0.4)
Net income (loss) attributable to common shareholders for earnings per share	$ (22.6)	$ 12.0	$ (12.0)	$ 21.4
Weighted Average Shares:
Weighted average common shares outstanding - basic	34,000,000	33,700,000	34,100,000	33,900,000
Additional shares from the assumed exercise of stock options		400,000		300,000
Weighted average common shares outstanding - diluted	34,000,000	34,100,000	34,100,000	34,200,000
Earnings (Loss) per share - basic and diluted:
Earnings (Loss) from continuing operations	$ (0.66)	$ 0.35	$ (0.35)	$ 0.64
Loss from discontinued operations				(0.01)
Earnings (Loss) per share - basic and diluted	$ (0.66)	$ 0.35	$ (0.35)	$ 0.63
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)		520,000		476,000
Stock options
Earnings (Loss) per share - basic and diluted:
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)				42,000