Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 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 Employees Covering Two Agreements | employee	50
Alaska Electric Light & Power [Member]
Loss Contingencies [Line Items]
Percentage Of Employees, Collective Bargaining Agreement	50.00%
Maximum [Member] | Market Manipulation Lawsuit [Member]
Loss Contingencies [Line Items]
Loss Contingency, Maximum | $	$ 16.0