Earnings per Share/Capital Stock: (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Additional disclosure
Options outstanding (in shares)	47,792	120,138
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	52,622	44,832
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans	$ 340	$ 40
Weighted Average Dividends Common Stock	9,362	8,854
Dividends paid	$ 9,362	$ 8,854
Dividends Declared Per Common Share (in dollars per share)	$ 0.255	$ 0.242
Restricted Stock Units
Additional disclosure
Restricted stock units outstanding (in shares)	193,740	194,031
Golden State Water Company [Member]
Additional disclosure
Dividends paid	$ 9,380	$ 0