Fair Value Measurement (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 335,413	$ 335,551
Investment in California Water Service Group	9,220	8,885
Quoted Prices in Active Markets for Identical Assets, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in California Water Service Group	9,220	8,885
Significant Observable Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	410,847	395,684
Investment in California Water Service Group	0	0
Significant Unobservable Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment in California Water Service Group	$ 0	$ 0