Business Segment Information (Details 3) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May. 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May. 31, 2015	May. 31, 2014	May. 31, 2013
Business Segment Information
Sales	$ 415.8	$ 380.1	$ 403.3	$ 395.1	$ 420.6	$ 399.8	$ 458.9	$ 429.8	$ 1,594.3	$ 1,709.1	$ 1,807.9
U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Sales									$ 493.1	$ 661.7	$ 733.7
Percentage of total sales									30.90%	38.70%	40.60%
Aviation Services
Business Segment Information
Sales									$ 1,316.1	$ 1,231.2	$ 1,246.9
Aviation Services | U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Sales									237.3	199.1	192.1
Expeditionary Services
Business Segment Information
Sales									278.2	477.9	561.0
Expeditionary Services | U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Sales									$ 255.8	$ 462.6	$ 541.6