Income Tax - Narrative (Details) (USD $)	May 31, 2014	May 31, 2013	May 31, 2012	May 31, 2010
Income Tax Disclosure [Abstract]
Deferred tax liability not recognized	$ 577,000,000
Basis difference - U.K. business	96,720,000	90,678,000
Unrecognized tax benefits	67,576,000	53,763,000	45,595,000	37,197,000
Unrecognized that would impact effective tax rate	$ 2,500,000