Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 05, 2017
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Trading Symbol	AAT
Entity Registrant Name	AMERICAN ASSETS TRUST, INC.
Entity Central Index Key	0001500217
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		47,113,653
American Assets Trust, L.P.
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Entity Registrant Name	AMERICAN ASSETS TRUST, L.P.
Entity Central Index Key	0001509570
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer