Document And Entity Information	3 Months Ended
	Mar. 31, 2012	May 04, 2012
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2012
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2012
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		39,286,206