Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Earnings per Share
Effect, participating securities			$ 0.0
Basic and Diluted EPS:
Income from continuing operations	$ 20.8	$ 14.4	32.0	$ 0.5
Less income attributable to participating shares	(0.1)	(0.1)	(0.2)	0.0
Income from continuing operations attributable to common shareholders	20.7	14.3	31.8	0.5
Income (Loss) from discontinued operations attributable to common shareholders	0.0	(6.2)	0.3	(6.8)
Net income (loss) attributable to common stockholders for earnings per share	$ 20.7	$ 8.1	$ 32.1	$ (6.3)
Weighted Average Shares:
Weighted average common shares outstanding - basic	35,100,000	34,900,000	35,100,000	34,900,000
Additional shares from assumed exercise of stock options	500,000	100,000	500,000	100,000
Weighted average common shares outstanding - diluted	35,600,000	35,000,000.0	35,600,000	35,000,000.0
Earnings (Loss) per share - basic:
Earnings from continuing operations	$ 0.59	$ 0.41	$ 0.90	$ 0.01
Income (Loss) from discontinued operations	0	(0.18)	0.01	(0.20)
Earnings (Loss) per share - basic	0.59	0.23	0.91	(0.19)
Earnings (Loss) per share - diluted:
Earnings from continuing operations	0.58	0.41	0.89	0.01
Income (Loss) from discontinued operations	0	(0.18)	0.01	(0.19)
Earnings (Loss) per share - diluted	$ 0.58	$ 0.23	$ 0.90	$ (0.18)
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)	0	1,743,000	0	1,743,000