Property, Plant And Equipment (Major Classifications Of Property, Plant And Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items]
Construction work-in-progress (CWIP) and other	$ 150,474	$ 202,683
Total	5,656,973	5,331,875
Other intangibles, property and investments-net	72,224	59,733
Total	5,687,737	5,357,584
Avista Utilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	5,434,977	5,125,650
Avista Utilities [Member] | Electric [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	1,346,332	1,217,179
Transmission	682,529	640,586
Distribution	1,525,175	1,468,157
Construction work-in-progress (CWIP) and other	296,912	358,846
Total	3,850,948	3,684,768
Avista Utilities [Member] | Natural Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	954,298	878,982
Construction work-in-progress (CWIP) and other	57,601	62,024
Natural gas underground storage	44,672	43,080
Total	1,056,571	984,086
Avista Utilities [Member] | Common Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	527,458	456,796
Alaska Electric Light & Power [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	221,996	206,225
Alaska Electric Light & Power [Member] | Electric [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	94,839	72,292
Transmission	20,252	18,817
Distribution	20,057	19,005
Capital Lease Assets	71,007	71,007
Construction work-in-progress (CWIP) and other	7,190	16,971
Total	213,345	198,092
Alaska Electric Light & Power [Member] | Common Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	8,651	8,133
Corporate and Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other intangibles, property and investments-net	30,764	25,709
Accumulated depreciation	$ 11,200	$ 10,600