Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Aug. 31, 2023	Aug. 31, 2022
Earnings per Share
Effect, participating securities	$ 0.0
Basic and Diluted EPS:
Income (Loss) from continuing operations	(0.6)	$ 22.3
Less income attributable to participating shares		(0.3)
Income (Loss) from continuing operations attributable to common shareholders	(0.6)	22.0
Income from discontinued operations attributable to common shareholders		0.4
Net income (loss) attributable to common shareholders for earnings per share, Basic	(0.6)	22.4
Net income (loss) attributable to common shareholders for earnings per share, Diluted	$ (0.6)	$ 22.4
Weighted Average Shares:
Weighted average common shares outstanding-basic	34,700,000	34,900,000
Additional shares from assumed exercise of stock options	400,000	500,000
Weighted average common shares outstanding-diluted	35,100,000	35,400,000
Earnings (Loss) per share - basic:
Earnings (Loss) from continuing operations	$ (0.02)	$ 0.63
Income from discontinued operations		0.01
Earnings (Loss) per share - basic	(0.02)	0.64
Earnings (Loss) per share - diluted:
Earnings (Loss) from continuing operations	(0.02)	0.62
Income from discontinued operations		0.01
Earnings (Loss) per share - diluted	$ (0.02)	$ 0.63
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)		230,000