Commitments And Contingencies (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) employee
Avista Utilities [Member]
Loss Contingencies [Line Items]
Percentage Of Employees, Collective Bargaining Agreement	45.00%
Majority Of Bargaining Unit Employees, Percentage	90.00%
Number Of Bargaining Unit Employees Oregon | employee	50
Alaska Electric Light & Power [Member]
Loss Contingencies [Line Items]
Percentage Of Employees, Collective Bargaining Agreement	54.00%
WASHINGTON
Loss Contingencies [Line Items]
Public Utilities Property Plant And Equipment Proposed Amount Of Disallowed Costs For Recently Completed Plant	$ 12.7
IDAHO
Loss Contingencies [Line Items]
Public Utilities Property Plant And Equipment Proposed Amount Of Disallowed Costs For Recently Completed Plant	$ 1.2