Earnings (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2024	Nov. 30, 2023	Nov. 30, 2024	Nov. 30, 2023
Basic and Diluted EPS:
Net income (loss)	$ (30.6)	$ 23.8	$ (12.6)	$ 23.2
Less income attributable to participating shares		(0.3)		(0.3)
Net income (loss) attributable to common shareholders for earnings (loss) per share	$ (30.6)	$ 23.5	$ (12.6)	$ 22.9
Weighted Average Shares:
Weighted average common shares outstanding-basic	35.2	34.9	35.2	34.9
Additional shares from the assumed exercise of stock options		0.4		0.4
Weighted average common shares outstanding-diluted	35.2	35.3	35.2	35.3
Earnings (Loss) per share - basic:
Earnings (Loss) per share - basic	$ (0.87)	$ 0.67	$ (0.36)	$ 0.66
Earnings (Loss) per share - diluted:
Earnings (Loss) per share - diluted	$ (0.87)	$ 0.67	$ (0.36)	$ 0.65
Impact of Net Loss on Participating Securities			$ 0.0