Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Aug. 31, 2016	Aug. 31, 2015
Earnings Per Share
Effect to the participating securities as result of net loss	$ 0.0
Basic and Diluted EPS:
Income from continuing operations	9.9	$ 7.4
Less income attributable to participating shares	(0.1)	(0.2)
Income from continuing operations attributable to common shareholders	9.8	7.2
Income from discontinued operations attributable to common shareholders	(0.4)	15.5
Net income attributable to common shareholders for earnings per share	$ 9.4	$ 22.7
Weighted Average Shares:
Weighted average common shares outstanding - basic	33,900,000	34,700,000
Additional shares from the assumed exercise of stock options	200,000	400,000
Weighted average common shares outstanding - diluted	34,100,000	35,100,000
Earnings per share - basic:
Earnings from continuing operations	$ 0.29	$ 0.21
Earnings (Loss) from discontinued operations	(0.01)	0.44
Earnings per share - basic	0.28	0.65
Earnings per share - diluted:
Earnings from continuing operations	0.29	0.21
Earnings (Loss) from discontinued operations	(0.01)	0.44
Earnings per share - diluted	$ 0.28	$ 0.65
Antidilutive stock options excluded from the computation of diluted earnings per share (in shares)	2,041,000	148,000