Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	Jun. 30, 2017	Nov. 30, 2016
Document and Entity Information
Entity Registrant Name	AAR CORP
Entity Central Index Key	0000001750
Document Type	10-K
Document Period End Date	May 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--05-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,355
Entity Common Stock, Shares Outstanding		34,396,501
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY