Selected Quarterly Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Sales	$ 492.3	$ 446.7	$ 423.8	$ 404.8	$ 468.6	$ 412.1	$ 431.5	$ 386.7	$ 1,767.6	$ 1,698.9	$ 1,621.4
Gross profit	79.8	69.0	66.2	61.5	65.6	59.3	59.1	53.9	276.5	237.9	130.8
Income (Loss) from continuing operations	15.1	13.1	12.1	9.9	11.8	9.9	9.2	7.4	50.2	38.3	(73.9)
Income (Loss) from discontinued operations	6.1	0.6		(0.4)	0.2	(5.1)	(1.2)	15.5	6.3	9.4	84.1
Net income	$ 21.2	$ 13.7	$ 12.1	$ 9.5	$ 12.0	$ 4.8	$ 8.0	$ 22.9	$ 56.5	$ 47.7	$ 10.2
Earnings (Loss) per share - basic:
Earnings (Loss) from continuing operations	$ 0.44	$ 0.39	$ 0.35	$ 0.29	$ 0.35	$ 0.29	$ 0.26	$ 0.21	$ 1.47	$ 1.10	$ (1.90)
Earnings (Loss) from discontinued operations	0.18	0.02		(0.01)		(0.15)	(0.03)	0.44	0.19	0.27	2.16
Earnings per share - basic	0.62	0.41	0.35	0.28	0.35	0.14	0.23	0.65	1.66	1.37	0.26
Earnings (Loss) per share - diluted:
Earnings (Loss) from continuing operations	0.44	0.38	0.35	0.29	0.34	0.29	0.26	0.21	1.45	1.10	(1.90)
Earnings (Loss) from discontinued operations	0.18	0.02		(0.01)		(0.15)	(0.03)	0.44	0.19	0.27	2.14
Earnings per share - diluted	$ 0.62	$ 0.40	$ 0.35	$ 0.28	$ 0.34	$ 0.14	$ 0.23	$ 0.65	$ 1.64	$ 1.37	$ 0.24
Telair Cargo Group
Earnings (Loss) per share - diluted:
Gain on sale of assets								$ 27.7