Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - USD ($) $ in Thousands		12 Months Ended
		May 31, 2018	May 31, 2017	May 31, 2016
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year		$ 20,525	$ 19,103	$ 15,497
Additions	[1]	13,358	6,446	8,274
Deductions	[2]	373	5,024	4,668
Balance at End of Year		33,510	20,525	19,103
Reserve for Obsolete Inventory
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year		38,305	32,716	30,531
Additions	[1]	1,335	10,049	5,195
Deductions	[2]	2,597	4,460	3,010
Balance at End of Year		$ 37,043	$ 38,305	$ 32,716

[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 as well as an estimate based on Cintas' historical rates of obsolescence.

[2] 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.