Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Materials and supplies	$ 37,101	$ 32,483
Fuel stock	4,273	5,142
Stored natural gas	12,774	28,731
Total	$ 54,148	$ 66,356