v2.4.0.6
Document and Entity Information (USD $)
12 Months Ended
Dec. 31, 2011
Mar. 08, 2012
Jun. 30, 2011
Document and Entity Information      
Entity Registrant Name AMERICAN STATES WATER CO    
Entity Central Index Key 0001056903    
Document Type 10-K    
Document Period End Date Dec. 31, 2011    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Accelerated Filer    
Entity Public Float   $ 699,832,000 $ 647,459,000
Entity Common Stock, Shares Outstanding   18,848,158  
Document Fiscal Year Focus 2011    
Document Fiscal Period Focus FY