Income Taxes - Components of Deferred Income Taxes (Details) - USD ($) $ in Thousands	May 31, 2021	May 31, 2020	May 31, 2019
Deferred tax assets:
Reserves related to accounts receivable	$ 10,292	$ 14,718
Inventory obsolescence	30,617	13,744
Insurance reserves	45,802	45,197
Stock-based compensation	74,898	78,802
Net operating loss and foreign related carry-forwards	3,885	7,657
Treasury locks	3,140	39,046
Operating lease liabilities	44,530	42,191
Deferred compensation and other	107,528	73,562
Deferred tax assets, gross	320,692	314,917
Valuation allowance	(2,037)	(6,411)	$ (7,308)
Deferred tax assets, net	318,655	308,506
Deferred tax liabilities:
Uniform and other rental items in service	202,846	189,787
Property and equipment	167,622	177,664
Service contracts and other intangible assets	207,834	207,610
Capitalized contract costs	79,356	77,741
Operating lease right-of-use assets	44,530	42,191
State taxes and other	3,114	2,092
Deferred tax liabilities	705,302	697,085
Net deferred tax liability	$ 386,647	$ 388,579