Business Segment Information - Sales by Product and Services (Details) - USD ($) $ 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
Net 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
Aviation supply chain
Net sales									998.7	903.2	847.6
Maintenance, repair and overhaul services
Net sales									486.7	521.8	468.5
Expeditionary airlift services
Net sales									176.8	173.4	173.3
Mobility products
Net sales									$ 105.4	$ 100.5	$ 132.0