CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 17, 2009	Nov. 17, 2010
Cal Water
Long-term debt
Ownership interest (as a percent)	100.00%	100.00%	100.00%
All Other Subsidiaries
Long-term debt
Ownership interest (as a percent)	100.00%	100.00%	100.00%
First Mortgage Bonds, 5.875% due 2019
Long-term debt
Interest rate (as a percent)	5.875%	5.875%
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
Long-term debt
Interest rate (as a percent)	5.50%	5.50%
First Mortgage Bonds, 5.500% due 2040 | Cal Water
Long-term debt
Debt issued					$ 100
Interest rate (as a percent)	5.50%