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%