Earnings per Share/Capital Stock: (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Capital stock
Net income	$ 14,072	$ 12,852
Total income available to common shareholders, basic	$ 14,026	$ 12,792
Additional disclosure
Options outstanding (in shares)	0	29,160
Anti-dilutive stock options not included in the computation of diluted EPS (in shares)		0
Common Shares issued under DRP and the 2000 and 2008 Employee Plans	37,157	37,376
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans	$ 30	$ 75
Payments Related to Tax Withholding for Share-based Compensation	(1,809)	(1,569)
Weighted Average Dividends Common Stock	11,242	10,113
Dividends paid	$ 11,242	$ 10,113
Dividends Declared Per Common Share (in dollars per share)	$ 0.305	$ 0.275
Preferred Stock Dividends and Other Adjustments	$ 37	$ 47
Undistributed Earnings, Basic	2,793	2,692
Undistributed earnings allocated to common shareholders	2,784	2,679
Undistributed earnings allocated to participating securities	$ 9	$ 13
Weighted average Common Shares outstanding, basic (in shares)	36,860,000	36,773,000
Basic earnings per Common Share (in dollars per share)	$ 0.38	$ 0.35
Restricted Stock Units
Additional disclosure
Restricted stock units outstanding (in shares)	129,637	184,833
ASUS
Additional disclosure
Dividends paid	$ 11,300
GOLDEN STATE WATER COMPANY
Capital stock
Net income	11,202	$ 9,022
Additional disclosure
Payments Related to Tax Withholding for Share-based Compensation	(1,610)	(1,308)
Dividends paid	$ 11,250	$ 10,100