Fair Value Measurement (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 385,138	$ 335,551
Investment in California Water Service Group	5,815	8,885
Quoted Prices in Active Markets for Identical Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in California Water Service Group	5,815	8,885
Significant Observable Inputs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	469,092	395,684
Investment in California Water Service Group	0	0
Significant Unobservable Inputs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in California Water Service Group	$ 0	$ 0