Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2017	May 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,839,878	$ 2,411,646
Less: accumulated depreciation	1,516,377	1,417,954
Property, plant and equipment, net	1,323,501	993,692
Capitalized interest	2,100	1,100
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	173,166	117,881
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	624,615	509,193
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,930,018	1,582,793
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	32,679	28,412
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 79,400	$ 173,367