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Revenue from Contract with Customer (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Disaggregation of Revenue [Line Items]        
Contract with Customer, Liability, Revenue Recognized $ 2,600   $ 1,900  
Revenue, Remaining Performance Obligation 0   $ 0  
Registration Payment Arrangement, Term     20 days  
Golden State Water Company [Member]        
Disaggregation of Revenue [Line Items]        
Cost of Reimbursable Expense $ 894 $ 937 $ 1,700 $ 1,800
Contracted Services [Member] | American States Utility Services [Member]        
Disaggregation of Revenue [Line Items]        
Period of Fixed Price Contracts to Operate and Maintain Water Systems at Various Military Bases     50 years  
Sales [Member] | Water Service Utility Operations [Member] | Golden State Water Company [Member]        
Disaggregation of Revenue [Line Items]        
Concentration Risk, Percentage     90.00%  
Sales [Member] | Electric Service Utility Operations [Member] | Golden State Water Company [Member]        
Disaggregation of Revenue [Line Items]        
Concentration Risk, Percentage     85.00%  
Minimum [Member] | American States Utility Services [Member]        
Disaggregation of Revenue [Line Items]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period     36 years  
Maximum [Member] | American States Utility Services [Member]        
Disaggregation of Revenue [Line Items]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period     50 years