Summary Of Significant Accounting Policies (Goodwill) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Jul. 01, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill		$ 57,672	$ 57,976	$ 52,426	$ 76,257
Adjustments		(304)	112
Goodwill sold during the year			71,123
Goodwill acquired during the year			52,730
Accumulated Impairment Losses [Member]
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss		7,733	7,733		7,733
Adjustments		0	0
Goodwill sold during the year			0
Goodwill acquired during the year			0
Ecova [Member]
Goodwill [Line Items]
Goodwill		0	0		71,011
Adjustments		0	112
Goodwill sold during the year			71,123
Goodwill acquired during the year			0
Alaska Electric Light & Power [Member]
Goodwill [Line Items]
Goodwill	$ 52,400	52,426	52,730		0
Adjustments	$ (300)	(304)	0
Goodwill sold during the year			0
Goodwill acquired during the year			52,730
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill		12,979	12,979		$ 12,979
Adjustments		$ 0	0
Goodwill sold during the year			0
Goodwill acquired during the year			$ 0