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Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($) employee
2015 Washington General Rate Case [Member] |
Loss Contingencies [Line Items] |
Loss Contingency Accrual | $ 3.6
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
Minimum [Member] | 2015 Washington General Rate Case [Member] |
Loss Contingencies [Line Items] |
Loss Contingency, Estimate of Possible Loss | $ 3.6
Maximum [Member] | 2015 Washington General Rate Case [Member] |
Loss Contingencies [Line Items] |
Loss Contingency, Estimate of Possible Loss | 77.0
Electricity [Member] | Maximum [Member] | 2015 Washington General Rate Case [Member] |
Loss Contingencies [Line Items] |
Loss Contingency, Estimate of Possible Loss | $ 20.0

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