Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	May 31, 2023	May 31, 2022	May 31, 2024	May 31, 2023	May 31, 2022
Basic and Diluted EPS:
Income from continuing operations			$ 46.3	$ 89.8	$ 78.5
Less income attributable to participating shares			(0.5)	(1.1)	(0.6)
Income from continuing operations attributable to common stockholders			45.8	88.7	77.9
Income from discontinued operations attributable to common shareholders				0.4	0.2
Net income attributable to common stockholders for earnings per share, Basic			45.8	89.1	78.1
Net income attributable to common stockholders for earnings per share, Diluted			$ 89.1	$ 78.1	$ 35.4
Weighted Average Shares:
Weighted average common shares outstanding-basic			35,100,000	34,700,000	35,600,000
Additional shares from the assumed exercise of stock options			300,000	400,000	400,000
Weighted average common shares outstanding-diluted			35,400,000	35,100,000	36,000,000.0
Earnings per share - basic:
Earnings from continuing operations			$ 1.30	$ 2.55	$ 2.19
Income from discontinued operations				0.01	0.01
Earnings per share - basic			1.30	2.56	2.20
Earnings per share - diluted:
Earnings from continuing operations			1.29	2.52	2.16
Income from discontinued operations				0.01	0.01
Earnings per share - diluted			$ 1.29	$ 2.53	$ 2.17
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)	197,300	229,800
Impact of Net Loss on Participating Securities			$ 0.0