Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Materials and supplies	$ 39,487	$ 37,101
Fuel stock	4,754	4,273
Natural gas stored	13,839	12,774
Total	$ 58,080	$ 54,148