Cover Page - shares	9 Months Ended
	Sep. 30, 2023	Oct. 27, 2023
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity Registrant Name	AMERICAN ASSETS TRUST, INC.
Entity File Number	001-35030
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	27-3338708
Entity Address, Address Line One	3420 Carmel Mountain Road
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	350-2600
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	AAT
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		60,724,630
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001500217
Current Fiscal Year End Date	--12-31
American Assets Trust, L.P.
Entity Information [Line Items]
Entity Registrant Name	AMERICAN ASSETS TRUST, L.P.
Entity File Number	333-202342-01
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	27-3338894
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0001509570