Earnings per Share/Capital Stock: (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Capital stock
Net income	$ 28,006	$ 26,784	$ 12,852	$ 22,952	$ 16,348	$ 10,782	$ 67,642	$ 50,082
Total income available to common shareholders, basic	$ 27,881			$ 22,829			$ 67,348	$ 49,822
Additional disclosure
Options outstanding (in shares)	8,556			47,792			8,556	47,792
Anti-dilutive stock options not included in the computation of diluted EPS (in shares)	0						0	0
Common Shares issued under DRP and the 2000 and 2008 Employee Plans							81,459	64,245
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans				$ 348			$ 416
Payments Related to Tax Withholding for Share-based Compensation							(1,581)	$ (1,217)
Weighted Average Dividends Common Stock	$ 11,234			$ 10,102			31,466	28,831
Dividends paid							$ 31,466	$ 28,831
Dividends Declared Per Common Share (in dollars per share)	$ 0.305			$ 0.275			$ 0.855	$ 0.785
Preferred Stock Dividends and Other Adjustments	$ 50			$ 54			$ 137	$ 151
Undistributed Earnings, Basic	16,722			12,796			36,039	21,100
Undistributed earnings allocated to common shareholders	16,647			12,727			35,882	20,991
Undistributed earnings allocated to participating securities	$ 75			$ 69			$ 157	$ 109
Weighted average Common Shares outstanding, basic (in shares)	36,835,000			36,737,000			36,804,000	36,728,000
Basic earnings per Common Share (in dollars per share)	$ 0.76			$ 0.62			$ 1.83	$ 1.36
Restricted Stock Units
Additional disclosure
Restricted stock units outstanding (in shares)	165,783			198,613			165,783	198,613
ASUS
Additional disclosure
Dividends paid	$ 11,300
Golden State Water Company [Member]
Capital stock
Net income	$ 23,362	$ 22,298	$ 9,022	$ 17,919	$ 13,648	$ 8,890	$ 54,682	$ 40,457
Additional disclosure
Payments Related to Tax Withholding for Share-based Compensation							(1,317)	(1,055)
Dividends paid				$ 10,100			$ 20,200	$ 28,850