Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended					6 Months Ended
	Nov. 30, 2014 segment		Aug. 31, 2014 segment	Nov. 30, 2013		Nov. 30, 2014		Nov. 30, 2013		May 31, 2014
Disclosures related to operating segments
Number of Reportable Segments	3		4
Revenue	$ 1,123,379			$ 1,123,931		$ 2,225,456		$ 2,224,177
Income (loss) before income taxes	165,265			135,810		340,581		258,967
Total assets	4,697,571			4,365,398		4,697,571		4,365,398		4,462,452
Rental Uniforms and Ancillary Products
Disclosures related to operating segments
Revenue	865,428			804,316		1,722,300		1,597,182
Income (loss) before income taxes	156,480			126,070		299,161		243,463
Total assets	2,939,994			2,838,831		2,939,994		2,838,831
Uniform Direct Sales
Disclosures related to operating segments
Revenue	117,521			121,883		222,666		229,345
Income (loss) before income taxes	10,370			13,864		19,557		22,545
Total assets	138,306			159,465		138,306		159,465
First Aid, Safety and Fire Protection
Disclosures related to operating segments
Revenue	140,430			124,585		280,490		250,460
Income (loss) before income taxes	14,733			10,585		26,353		22,031
Total assets	429,800			418,787		429,800		418,787
Corporate
Disclosures related to operating segments
Revenue	0	[1]		73,147	[1]	0	[1]	147,190	[1]
Income (loss) before income taxes	(16,318)	[1]		(14,709)	[1]	(4,490)	[1]	(29,072)	[1]
Total assets	1,189,471	[1]		948,315	[1]	1,189,471	[1]	948,315	[1]
Cintas Document Shredding
Disclosures related to operating segments
Revenue				73,100				147,200
Income (loss) before income taxes				1,700				3,800
Total assets				$ 480,800				$ 480,800

[1] Corporate assets as of November 30, 2014 include the investment in the Shred-it partnership. Corporate assets also include the real estate assets of the document storage and imaging business that were not included in the sale transactions. Corporate assets as of November 30, 2013 include the assets of the document storage and imaging business. Corporate results for the three months ended November 30, 2013 include the revenue ($73.1 million) and income before income taxes ($1.7 million) of the document shredding business. Corporate results and assets as of and for the six months ended November 30, 2013 include the revenue ($147.2 million), income before income taxes ($3.8 million) and assets ($480.8 million) of the document shredding business.