Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	May 31, 2019	Jun. 28, 2019	Nov. 30, 2018
Document and Entity Information
Document Type	10-K
Document Period End Date	May 31, 2019
Entity Registrant Name	AAR CORP
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,449
Entity Common Stock, Shares Outstanding		34,826,115
Entity Central Index Key	0000001750
Current Fiscal Year End Date	--05-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Amendment Flag	false