California Water Service Group Stock Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Available for Sale Marketable Security, Shares Sold	159,151		125,969
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 4,510		$ 3,056
Fees Incurred on Sale of Available for Sale Securities	20		10
Available-for-sale Securities, Gross Realized Gain (Loss)	3,197	$ 0	2,017
Available for Sales Securities, Tax on Realized Gain	1,303		822
Gain (Loss) on Sale of Securities, Net	1,894		1,195
Reclassification adjustment from AOCI for sale of securities, net	$ 1,742	0	$ 1,171
Shares of California Water Service Group held	100,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Investment in California Water Service Group	$ 3,390	$ 6,030

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

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The net gain (loss) realized from the sale, exchange, redemption, or retirement of securities, not separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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