Common Shareholders' Equity - summary of status of options granted under all employee plans (Details 2) (Stock Options, USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding	108,500	306,500
Granted
Expired	7,500	8,000
Exercised	80,000	78,000
Surrendered		112,000
Outstanding	21,000	108,500	306,500
Exercisable, Options	21,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding	$ 3.60	$ 3.49
Granted
Expired	$ 4.7	$ 4.38
Exercised	$ 3.21	$ 2.05
Surrendered		$ 4.33
Outstanding	$ 4.70	$ 3.60	$ 3.49
Exercisable, Weighted Average Exercise Price	$ 4.70
Outstanding, Weighted Average Remaining Contractual Life	3 years	2 years 11 months 16 days	2 years 6 months 18 days
Outstanding, Aggregate Intrinsic Value	$ 65,100
Exercisable, Weighted Average Remaining Contractual Life	3 years
Exercisable, Aggregate Intrinsic Value	$ 65,100