Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Amortizable intangible assets:
Gross carrying amount	$ 57.9	$ 183.3
Accumulated amortization	(22.5)	(36.2)
Net carrying amount	35.4	147.1
Unamortized intangible assets:
Trademarks	1.3	18.3
Intangible Assets, Gross (Excluding Goodwill)	59.2	201.6
Intangible Assets, Net (Excluding Goodwill), Total	36.7	165.4
Amortization expense	4.6	4.7	$ 7.7
Estimated aggregate amortization expense for intangible assets in each of the next five fiscal years
2016	4.4
2017	4.4
2018	4.4
2019	3.8
2020	3.5
Capitalized Program Development Costs
Net costs capitalized associated with the engineering and development of the cargo system, current and noncurrent		139.8
Net costs capitalized associated with the engineering and development of the cargo system, current		27.6
Capitalized program development costs		112.2
Customer relationships
Amortizable intangible assets:
Gross carrying amount	23.4	124.0
Accumulated amortization	(9.0)	(22.9)
Net carrying amount	$ 14.4	101.1
Customer relationships | Minimum
Unamortized intangible assets:
Useful life	10 years
Customer relationships | Maximum
Unamortized intangible assets:
Useful life	20 years
Developed technology
Amortizable intangible assets:
Gross carrying amount	$ 8.0	32.8
Accumulated amortization	(3.5)	(4.8)
Net carrying amount	$ 4.5	28.0
Developed technology | Minimum
Unamortized intangible assets:
Useful life	7 years
Developed technology | Maximum
Unamortized intangible assets:
Useful life	10 years
Lease agreements
Amortizable intangible assets:
Gross carrying amount	$ 21.5	21.5
Accumulated amortization	(8.7)	(7.5)
Net carrying amount	$ 12.8	14.0
Unamortized intangible assets:
Useful life	18 years
FAA certificates
Amortizable intangible assets:
Gross carrying amount	$ 5.0	5.0
Accumulated amortization	(1.3)	(1.0)
Net carrying amount	$ 3.7	$ 4.0
Unamortized intangible assets:
Useful life	20 years