California Water Service Group Stock Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Available for Sale Marketable Security, Shares Sold	125,969
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 3,056
Fees Incurred on Sale of Available for Sale Securities	10
Available-for-sale Securities, Gross Realized Gain (Loss)	2,017	$ 0	$ 2,017	$ 0
Available for Sales Securities, Tax on Realized Gain	822
Gain (Loss) on Sale of Securities, Net	1,195
Reclassification adjustment from AOCI for sale of securities, net	$ 1,171	$ 0	1,171	$ 0
Shares of California Water Service Group held		259,151
Quoted Prices in Active Markets for Identical Assets (Level 1)
Investment in California Water Service Group		$ 6,030	$ 6,378

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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