California Water Service Group Stock Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares of California Water Service Group held		100,000
Available for Sale Marketable Security, Shares Sold	159,151
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 4,510
Fees Incurred on Sale of Available for Sale Securities	20
Available-for-sale Securities, Gross Realized Gain (Loss)	3,197	$ 0	$ 3,197	$ 0
Available for Sales Securities, Tax on Realized Gain	1,303
Gain (Loss) on Sale of Securities, Net	1,894
Reclassification adjustment from AOCI for sale of securities, net	$ 1,742	0	1,742	$ 0
Quoted Prices in Active Markets for Identical Assets (Level 1)
Investment in California Water Service Group		$ 4,535	$ 3,390