v3.7.0.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2017
Apr. 28, 2017
Document and Entity Information    
Entity Registrant Name AMERICAN STATES WATER CO  
Entity Central Index Key 0001056903  
Document Type 10-Q  
Document Period End Date Mar. 31, 2017  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   36,616,192
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q1