Property, Plant And Equipment (Major Classifications Of Property, Plant And Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Public Utility, Property, Plant and Equipment [Line Items]
Construction work-in-progress (CWIP) and other	$ 202,683	$ 227,758
Total	5,331,875	4,945,820
Other intangibles, property and investments-net	50,750	42,016
Total	5,357,584	4,971,623
Avista Utilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	5,125,650	4,750,468
Avista Utilities [Member] | Electric [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	1,217,179	1,171,002
Transmission	640,586	603,909
Distribution	1,468,157	1,360,185
Construction work-in-progress (CWIP) and other	358,846	311,807
Total	3,684,768	3,446,903
Avista Utilities [Member] | Natural Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	878,982	810,487
Construction work-in-progress (CWIP) and other	62,024	57,088
Natural gas underground storage	43,080	41,963
Total	984,086	909,538
Avista Utilities [Member] | Common Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	456,796	394,027
Alaska Electric Light & Power [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	206,225	195,352
Alaska Electric Light & Power [Member] | Electric [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	72,292	71,969
Transmission	18,817	18,392
Distribution	19,005	17,936
Public Utilities Property Plant And Equipment Capital Lease Assets	71,007	71,007
Construction work-in-progress (CWIP) and other	16,971	7,893
Total	198,092	187,197
Alaska Electric Light & Power [Member] | Common Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	8,133	8,155
Corporate and Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other intangibles, property and investments-net	25,709	25,803
Accumulated depreciation	$ 10,600	$ 10,800