Earnings per Share/Capital Stock: (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Capital stock
Net income	$ 25,612	$ 14,072	$ 26,784	$ 12,852	$ 39,684	$ 39,636
Total income available to common shareholders, basic	$ 25,521		$ 26,662		$ 39,549	$ 39,464
Additional disclosure
Options outstanding (in shares)	0		11,556		0	11,556
Anti-dilutive stock options not included in the computation of diluted EPS (in shares)					0	0
Common Shares issued under DRP and the 2000 and 2008 Employee Plans					37,260	73,854
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans					$ 30	$ 366
Payment, Tax Withholding, Share-based Payment Arrangement					1,809	1,573
Weighted Average Dividends Common Stock	$ 11,250		$ 10,119		22,492	20,232
Dividends paid					$ 22,492	$ 20,232
Dividends Declared Per Common Share (in dollars per share)	$ 0.305		$ 0.275		$ 0.610	$ 0.550
Preferred Stock Dividends and Other Adjustments	$ 40		$ 46		$ 77	$ 88
Undistributed Earnings, Basic	14,322		16,619		17,115	19,316
Undistributed earnings allocated to common shareholders	14,271		16,543		17,057	19,232
Undistributed earnings allocated to participating securities	$ 51		$ 76		$ 58	$ 84
Weighted average Common Shares outstanding, basic (in shares)	36,884,000		36,804,000		36,872,000	36,788,000
Basic earnings per Common Share (in dollars per share)	$ 0.69		$ 0.72		$ 1.07	$ 1.07
Restricted Stock Units
Additional disclosure
Restricted stock units outstanding (in shares)	133,863		170,372		133,863	170,372
GOLDEN STATE WATER COMPANY
Capital stock
Net income	$ 20,919	$ 11,202	$ 22,298	$ 9,022	$ 32,121	$ 31,320
Additional disclosure
Payment, Tax Withholding, Share-based Payment Arrangement					1,610	1,310
Dividends paid	$ 11,300		$ 10,100		$ 22,500	$ 20,200