v3.3.1.900
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2016
Apr. 29, 2016
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2016  
Document Fiscal Year Focus 2016  
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   45,405,906
American Assets Trust, L.P.    
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2016  
Document Fiscal Year Focus 2016  
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