Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2023	Nov. 30, 2022	Nov. 30, 2023	Nov. 30, 2022
Earnings per Share
Effect, participating securities			$ 0.0
Basic and Diluted Earnings Per Share:
Income from continuing operations	$ 23.8	$ 22.5	23.2	$ 44.8
Less income attributable to participating shares	(0.3)	(0.3)	(0.3)	(0.6)
Income from continuing operations attributable to common shareholders	23.5	22.2	22.9	44.2
Income from discontinued operations attributable to common shareholders				0.4
Net income attributable to common shareholders for earnings per share, Basic	23.5	22.2	22.9	44.6
Net income attributable to common shareholders for earnings per share, Diluted	$ 23.5	$ 22.2	$ 22.9	$ 44.6
Weighted Average Shares:
Weighted average common shares outstanding-basic	34,900,000	34,200,000	34,900,000	34,600,000
Additional shares from the assumed exercise of stock options	400,000	500,000	400,000	400,000
Weighted average common shares outstanding-diluted	35,300,000	34,700,000	35,300,000	35,000,000.0
Earnings per share - basic:
Earnings from continuing operations	$ 0.67	$ 0.65	$ 0.66	$ 1.28
Income from discontinued operations				0.01
Earnings per share - basic	0.67	0.65	0.66	1.29
Earnings per share - diluted:
Earnings from continuing operations	0.67	0.64	0.65	1.26
Income from discontinued operations				0.01
Earnings per share - diluted	$ 0.67	$ 0.64	$ 0.65	$ 1.27
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)		447,000		229,000