Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Earnings per Share
Effect to the participating securities as result of net loss	$ 0.0
Basic and Diluted EPS:
Income from continuing operations	18.9	$ 11.0
Less income attributable to participating shares	(0.1)	(0.1)
Income from continuing operations attributable to common shareholders	18.8	10.9
Loss from discontinued operations attributable to common shareholders	(3.8)	(0.4)
Net income attributable to common shareholders for earnings per share	$ 15.0	$ 10.5
Weighted average common shares outstanding - basic	34,600,000	34,000,000
Additional shares from assumed exercise of stock options	500,000	500,000
Weighted average common shares outstanding - diluted	35,100,000	34,500,000
Earnings per share - basic:
Earnings from continuing operations	$ 0.54	$ 0.32
Loss from discontinued operations	(0.11)	(0.01)
Earnings per share - basic	0.43	0.31
Earnings per share - diluted:
Earnings from continuing operations	0.54	0.32
Loss from discontinued operations	(0.11)	(0.01)
Earnings per share - diluted	$ 0.43	$ 0.31
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)	290,000