Selected Quarterly Data (Unaudited) (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
Sales	$ 562.7	$ 529.5	$ 493.3	$ 466.3	$ 473.5	$ 456.3	$ 420.6	$ 397.9	$ 2,051.8	$ 1,748.3	$ 1,590.8
Operating income	29.3	29.8	16.8	22.4	22.8	24.3	21.8	17.1	98.3	86.0	82.3
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
Loss from discontinued operations	(3.8)	(64.8)	(4.2)	(3.8)	(6.1)	(15.8)	(35.8)	(0.4)	(76.6)	(58.1)	4.5
Net income (loss)	$ 22.8	$ (37.4)	$ 7.0	$ 15.1	$ 12.0	$ 15.5	$ (22.5)	$ 10.6	$ 7.5	$ 15.6	$ 56.5
Earnings (Loss) per share - basic:
Continuing operations	$ 0.77	$ 0.79	$ 0.32	$ 0.54	$ 0.53	$ 0.91	$ 0.39	$ 0.32	$ 2.42	$ 2.14	$ 1.53
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 (Loss) per share - diluted
Continuing operations	0.76	0.78	0.32	0.54	0.52	0.90	0.38	0.32	2.40	2.11	1.51
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
Discontinued Operations, Held-for-sale
Earnings (Loss) per share - diluted
Gain recognized on sale of business		$ 74.1
Impairment and other charges							$ 54.2
Goodwill impairment charge						$ 9.8