Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Materials and supplies	$ 34,957	$ 32,483
Fuel stock	4,802	5,142
Natural gas stored	19,976	28,731
Total	$ 59,735	$ 66,356