Schedule II - Valuation and Qualifying Accounts and Reserves (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2012		May 31, 2011		May 31, 2010
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 17,057		$ 14,297		$ 19,532
Charged to Costs and Expense	5,165	[1]	7,835	[1]	1,060	[1]
Charged to Other Accounts	194	[2]	43	[2]	(167)	[2]
Deductions	5,399	[3]	5,118	[3]	6,128	[3]
Balance at End of Year	17,017		17,057		14,297
Inventory Valuation Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	30,717		32,466		48,353
Charged to Costs and Expense	4,247	[1]	1,626	[1]	(7,979)	[1]
Charged to Other Accounts	(1,505)	[2]	(8)	[2]	(130)	[2]
Deductions	4,083	[3]	3,367	[3]	7,778	[3]
Balance at End of Year	$ 29,376		$ 30,717		$ 32,466

[1] Represents amounts charged to expense to increase reserve for estimated future bad debts or to increase reserve for obsolete inventory. Amounts related to inventory are computed by performing a thorough analysis of future marketability by specific inventory item.

[2] Represents a change in the appropriate balance sheet reserve due to acquisitions during the respective period.

[3] Represents reductions in the balance sheet reserve due to the actual write-off of non-collectible accounts receivable or the physical disposal of obsolete inventory items. These amounts do not impact Cintas' consolidated income statement.