California Water Service Group Stock (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Available for Sale Marketable Security, Shares Sold			17,660
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds			$ 716
Fees Incurred on Sale of Available for Sale Securities			2
Available-for-sale Securities, Gross Realized Gain (Loss)	$ 0	$ 0	(87)	$ 0
Available for Sales Securities, Tax on Realized Gain			(24)
Gain (Loss) on Sale of Securities, Net			$ (63)
Available for Sale Marketable Security, Shares Held	82,340		82,340