Business Segment Information - Sales by Product and Services (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Sales by type of product/service
Net sales	$ 458.2	$ 402.8	$ 423.8	$ 377.8	$ 415.8	$ 380.1	$ 403.3	$ 395.1	$ 1,662.6	$ 1,594.3	$ 1,709.1
Aviation supply chain
Sales by type of product/service
Net sales									903.2	847.6	755.7
Maintenance, repair and overhaul services
Sales by type of product/service
Net sales									521.8	468.5	475.5
Expeditionary airlift services
Sales by type of product/service
Net sales									173.4	173.3	328.8
Mobility products
Sales by type of product/service
Net sales									$ 64.2	$ 104.9	$ 149.1