Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2019	May 31, 2018	May 31, 2017
Earnings per Share
Effect to the participating securities as result of net loss									$ 0.0
Basic and Diluted EPS:
Income from continuing operations	$ 26.6	$ 27.4	$ 11.2	$ 18.9	$ 18.1	$ 31.3	$ 13.3	$ 11.0	84.1	$ 73.7	$ 52.0
Less income attributable to participating shares									(0.4)	(0.6)	(0.5)
Income from continuing operations attributable to common shareholders									83.7	73.1	51.5
Income (Loss) from discontinued operations attributable to common shareholders									(76.6)	(58.1)	4.5
Net income attributable to common shareholders for earnings per share									$ 7.1	$ 15.0	$ 56.0
Weighted Average Shares:
Weighted average common shares outstanding - basic									34,500,000	34,200,000	33,900,000
Additional shares from assumed exercise of stock options									400,000	400,000	400,000
Weighted average common shares outstanding - diluted									34,900,000	34,600,000	34,300,000
Earnings per share - basic:
Earnings from continuing operations	$ 0.77	$ 0.79	$ 0.32	$ 0.54	$ 0.53	$ 0.91	$ 0.39	$ 0.32	$ 2.42	$ 2.14	$ 1.53
Earnings (Loss) from discontinued operations	(0.11)	(1.87)	(0.12)	(0.11)	(0.18)	(0.46)	(1.05)	(0.01)	(2.22)	(1.70)	0.13
Earnings per share - basic	0.66	(1.08)	0.20	0.43	0.35	0.45	(0.66)	0.31	0.20	0.44	1.66
Earnings per share - diluted:
Earnings from continuing operations	0.76	0.78	0.32	0.54	0.52	0.90	0.38	0.32	2.40	2.11	1.51
Earnings (Loss) from discontinued operations	(0.11)	(1.86)	(0.12)	(0.11)	(0.18)	(0.46)	(1.05)	(0.01)	(2.19)	(1.70)	0.13
Earnings per share - diluted	$ 0.65	$ (1.08)	$ 0.20	$ 0.43	$ 0.34	$ 0.44	$ (0.67)	$ 0.31	$ 0.21	$ 0.41	$ 1.64
Antidilutive shares excluded from the computation of diluted earnings per share (in shares)									273,400		11,200