Summary of Significant Accounting Policies (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Amortizable intangible assets:
Gross carrying amount	$ 172,362	$ 68,419
Accumulated amortization	(34,094)	(21,323)
Net carrying amount	138,268	47,096
Unamortized intangible assets:
Carrying amount of trademarks	16,694
Carrying amount of intangible assets, other than goodwill	154,962	47,096
Amortization expense	12,971	9,613	4,567
Estimated aggregate amortization expense for intangible assets in each of the next five fiscal years
2013	12,943
2014	9,030
2015	8,981
2016	8,820
2017	8,820
Customer relationships
Amortizable intangible assets:
Gross carrying amount	113,384	39,449
Unamortized intangible assets:
Minimum useful life (in years)	1
Maximum useful life (in years)	20
Developed technology
Amortizable intangible assets:
Gross carrying amount	30,008
Unamortized intangible assets:
Minimum useful life (in years)	7
Maximum useful life (in years)	30
Lease agreements
Amortizable intangible assets:
Gross carrying amount	21,500	21,500
Unamortized intangible assets:
Useful life (in years)	18
FAA certificates
Amortizable intangible assets:
Gross carrying amount	5,000	5,000
Unamortized intangible assets:
Useful life (in years)	20
Covenants not to compete
Amortizable intangible assets:
Gross carrying amount	1,570	1,570
Unamortized intangible assets:
Useful life (in years)	3
Trademarks
Amortizable intangible assets:
Gross carrying amount	600	600
Other
Amortizable intangible assets:
Gross carrying amount	$ 300	$ 300