Earnings per Share/Capital Stock: (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		6 Months Ended					3 Months Ended	0 Months Ended
	May 20, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Restricted Stock Units	Jun. 30, 2013 Restricted Stock Units	Mar. 27, 2014 AWR	Jun. 30, 2014 AWR	May 20, 2014 Minimum AWR	May 20, 2014 Maximum AWR
Additional disclosure
Options outstanding (in shares)		245,784	281,668	245,784	281,668
Restricted stock units outstanding (in shares)						239,226	260,906
Stock options included in the calculation of diluted EPS (in shares)				245,784
Stock options not included in the calculation of diluted EPS (in shares)		0		0
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				70,573	208,986
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans				$ 219	$ 1,832
Common Shares repurchased in the open market under DRP and 401(k) Plan				192,188	481,224				9,300
Dividends paid		$ 7,900	$ 6,800	$ 15,699	$ 13,684
Quarterly dividends paid, per share of common stock (in dollars per share)		$ 0.2025	$ 0.1775	$ 0.405	$ 0.355
Percent change in quarterly dividend	5.20%
Authorized shares to be repurchased								1,250,000
Dividends, Preferred Stock, Cash										$ 0.2025	$ 0.2130