Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Earnings per Share
Effect, participating securities			$ 0.0
Basic and Diluted EPS:
Income from continuing operations	$ 2.6	$ 27.4	39.8	$ 57.5
Less income attributable to participating shares		(0.1)	(0.2)	(0.2)
Income from continuing operations attributable to common shareholders	2.6	27.3	39.6	57.3
Loss from discontinued operations attributable to common shareholders	(0.3)	(64.8)	(18.9)	(72.8)
Net income attributable to common shareholders for earnings per share	$ 2.3	$ (37.5)	$ 20.7	$ (15.5)
Weighted Average Shares:
Weighted average common shares outstanding - basic	34,700,000	34,500,000	34,800,000	34,600,000
Additional shares from the assumed exercise of stock options	400,000	400,000	300,000	400,000
Weighted average common shares outstanding - diluted	35,100,000	34,900,000	35,100,000	35,000,000.0
Earnings per share - basic:
Earnings from continuing operations	$ 0.08	$ 0.79	$ 1.14	$ 1.66
Loss from discontinued operations	(0.01)	(1.87)	(0.54)	(2.11)
Earnings (Loss) per share - basic	0.07	(1.08)	0.60	(0.45)
Earnings per share - diluted:
Earnings from continuing operations	0.07	0.78	1.13	1.63
Loss from discontinued operations	(0.01)	(1.86)	(0.54)	(2.08)
Earnings (Loss) per share - diluted	$ 0.06	$ (1.08)	$ 0.59	$ (0.45)
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)	265,000	277,000	265,000	277,000