Document And Entity Information	9 Months Ended
Sep. 30, 2011	Nov. 10, 2011
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2011
Entity Registrant Name	American Assets Trust, Inc.
Entity Central Index Key	0001500217
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		39,283,796

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