Property and Equipment (Details) (USD $)	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,143,663,000	$ 2,342,247,000
Less: accumulated depreciation	1,287,961,000	1,355,544,000
Property, plant and equipment, net	855,702,000	986,703,000
Interest expense, net of capitalized interest	0	0	1,300,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	116,989,000	112,311,000
Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	521,113,000	512,717,000
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,427,356,000	1,631,213,000
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	35,821,000	27,543,000
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 42,384,000	$ 58,463,000