Condensed Consolidating Financial Statements (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Apr. 17, 2009
Nov. 17, 2010
Cal Water        
Long-term debt        
Ownership interest (as a percent) 100.00% 100.00%    
All Other Subsidiaries        
Long-term debt        
Ownership interest (as a percent) 100.00% 100.00%    
First Mortgage Bonds, 5.875% due 2019 | Cal Water        
Long-term debt        
Debt issued     $ 100  
Interest rate (as a percent)     5.875%  
First Mortgage Bonds, 5.500% due 2040 | Cal Water        
Long-term debt        
Debt issued       $ 100
Interest rate (as a percent)       5.50%