Commitments And Contingencies (Schedule Of Cost Of Fuel Purchased And Transported As A Percentage Of Total Fuel Costs) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Hilcorp Alaska, LLC [Member]
Other Commitments [Line Items]
Cost of fuel purchased and transported as a percentage of total fuel costs	56.90%	30.30%	50.40%
ConocoPhillips (COP) [Member]
Other Commitments [Line Items]
Cost of fuel purchased and transported as a percentage of total fuel costs	32.00%	58.70%	43.60%
AIX Energy, LLC [Member]
Other Commitments [Line Items]
Cost of fuel purchased and transported as a percentage of total fuel costs	0.70%	4.70%	0.00%
ENSTAR [Member]
Other Commitments [Line Items]
Cost of fuel purchased and transported as a percentage of total fuel costs	4.70%	3.30%	2.00%
Harvest (Hilcorp) Pipeline [Member]
Other Commitments [Line Items]
Cost of fuel purchased and transported as a percentage of total fuel costs	3.20%	1.60%	3.00%
Miscellaneous [Member]
Other Commitments [Line Items]
Cost of fuel purchased and transported as a percentage of total fuel costs	2.50%	1.40%	1.00%