Summary of Significant Accounting Policies (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Amortizable intangible assets:
Gross carrying amount	$ 183.3	$ 165.5
Accumulated amortization	(36.2)	(25.1)
Net carrying amount	147.1	140.4
Unamortized intangible assets:
Trademarks	18.3	17.4
Carrying amount of intangible assets, other than goodwill	165.4	157.8
Amortization expense	10.4	13.7	13.0
Estimated aggregate amortization expense for intangible assets in each of the next five fiscal years
2015	10.5
2016	10.3
2017	10.3
2018	10.3
2019	9.8
Customer relationships
Amortizable intangible assets:
Gross carrying amount	124.0	108.0
Customer relationships | Minimum
Unamortized intangible assets:
Useful life	5 years
Customer relationships | Maximum
Unamortized intangible assets:
Useful life	20 years
Developed technology
Amortizable intangible assets:
Gross carrying amount	32.8	31.0
Developed technology | Minimum
Unamortized intangible assets:
Useful life	7 years
Developed technology | Maximum
Unamortized intangible assets:
Useful life	30 years
Lease agreements
Amortizable intangible assets:
Gross carrying amount	21.5	21.5
Unamortized intangible assets:
Useful life	18 years
FAA certificates
Amortizable intangible assets:
Gross carrying amount	$ 5.0	$ 5.0
Unamortized intangible assets:
Useful life	20 years