Segment Information (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Nov. 30, 2015 USD ($)	May. 31, 2015 USD ($) segment	Nov. 30, 2014 USD ($)	Nov. 30, 2015 USD ($)	Nov. 30, 2014 USD ($)
Segment Reporting Information
Number of operating segments | segment		3
Revenue	$ 1,219,080		$ 1,123,379	$ 2,417,970	$ 2,225,456
Income (loss) before income taxes	184,289		165,673	353,503	334,370
Total assets	4,450,792	$ 4,192,460	4,697,571	4,450,792	4,697,571
Operating Segments | Uniform Rental and Facility Services
Segment Reporting Information
Revenue	937,704		891,475	1,876,112	1,765,173
Income (loss) before income taxes	169,295		159,567	334,676	304,383
Total assets	2,995,616		2,907,484	2,995,616	2,907,484
Operating Segments | First Aid and Safety Services
Segment Reporting Information
Revenue	120,438		82,271	219,926	162,195
Income (loss) before income taxes	14,847		11,777	23,439	20,924
Total assets	426,673		263,996	426,673	263,996
Operating Segments | All Other
Segment Reporting Information
Revenue	160,938		149,633	321,932	298,088
Income (loss) before income taxes	16,207		10,239	27,741	19,764
Total assets	355,892		336,604	355,892	336,604
Corporate
Segment Reporting Information
Revenue	0		0	0	0
Income (loss) before income taxes	(16,060)		(15,910)	(32,353)	(10,701)
Total assets	$ 672,611		$ 1,189,487	$ 672,611	$ 1,189,487