Earnings Per Share and Capital Stock (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Additional disclosure
Stock options or restricted stock units included in the calculation of diluted EPS (in shares)	201,579
Common Shares issued under DRP and the 2000 and 2008 Employee Plans	38,519	69,434	68,025
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans		$ 1,658,000	$ 1,838,000
Common Shares authorized for issuance but unissued under DRP	527,974
Common Shares authorized for issuance but unissued under 401(k) Plan	193,650
Common Shares issued as a result of the exercise of stock options	409,700	88,713	30,500
Value of Common Shares issued as a result of the exercise of stock options		2,350,000	857,000
Exercise of stock options and other issuance of Common Shares	13,295,000
Common Shares repurchased in the open market under DRP and 401(k) Plan	675,967	441,410	143,034
Amount available for issuance of securities under registration statement	115,000,000
Restricted Stock Units
Additional disclosure
Stock options or restricted stock units included in the calculation of diluted EPS (in shares)	149,666
GSWC
Additional disclosure
Value of Common Shares issued under DRP and the 2000 and 2008 Employee Plans	$ 0	$ 10,000,000	$ 20,000,000