Commitments and Contingencies	3 Months Ended
Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 15. COMMITMENTS AND CONTINGENCIES In the course of its business, the Company becomes involved in various claims, controversies, disputes and other contingent matters, including the items described in this Note. Some of these claims, controversies, disputes and other contingent matters involve litigation or other contested proceedings. For all such matters, the Company intends to vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any particular matter because litigation and other contested proceedings are inherently subject to numerous uncertainties. For matters that affect Avista Utilities’ or AEL&P's operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process. Boyds Fire (State of Washington Department of Natural Resources v. Avista) In August 2019, the Company was served with a complaint, captioned “State of Washington Department of Natural Resources v. Avista Corporation,” seeking recovery up to $4.4 million for fire suppression and investigation costs and related expenses incurred in connection with a wildfire that occurred in Ferry County, Washington in August 2018. Specifically, the complaint alleges that the fire, which became known as the “Boyds Fire,” was caused by a dead ponderosa pine tree falling into an overhead distribution line, and that Avista Corp. was negligent in failing to identify and remove the tree before it came into contact with the line. Avista Corp. disputes that the tree in question was the cause of the fire and that it was negligent in failing to identify and remove it. Additional lawsuits have subsequently been filed by private landowners seeking property damages, and holders of insurance subrogation claims seeking recovery of insurance proceeds paid. The lawsuits were filed in the Superior Court of Ferry County, Washington and subsequently consolidated into a single action. The Company intends to vigorously defend itself in the litigation. However, the Company cannot predict the outcome of these matters. Labor Day Windstorm In September 2020, a severe windstorm occurred in eastern Washington and northern Idaho. The extreme weather event resulted in customer outages and the cause of multiple wildfires in the region. With respect to wildfires, the Company’s investigation determined that the primary cause of the fires was extreme high winds. To date, the Company has not found any evidence that the fires were caused by any deficiencies in its equipment, maintenance activities or vegetation management practices. The Company has become aware of instances where, during the course of the storm, otherwise healthy trees and limbs, located in areas outside its maintenance right-of-way, broke under the extraordinary wind conditions and caused damage to its energy delivery system at or near what is believed to be the potential area of origin of a wildfire. Those instances include what has been referred to as: the Babb Road fire (near Malden and Pine City, Washington); the Christensen Road fire (near Airway Heights, Washington); and the Mile Marker 49 fire (near Orofino, Idaho). These wildfires covered, in total, approximately 22,000 acres. The Company currently estimates approximately 230 residential, commercial and other structures were impacted. Parallel investigations by applicable state agencies, including the Washington Department of Natural Resources, are ongoing, and the Company is cooperating with those efforts. The Company’s investigation has found no evidence of negligence with respect to any of the fires, and the Company intends to vigorously defend any claims for damages that may be asserted against it with respect to the wildfires arising out of the extreme wind event. Colstrip The Washington CETA imposes deadlines by which coal-fired resources, such as Colstrip, must be excluded from the rate base of Washington utilities and by which electricity from such resources may no longer be delivered to Washington retail customers. Not all of the co-owners of Colstrip Units 3 & 4 are Washington utilities subject to CETA, and the co-owners have differing needs for the generating capacity of these units. Accordingly, business disagreements have arisen among the co-owners, including, but not limited to, disagreements as to the shut-down date or dates of these units. These business disagreements, in turn, have led to disagreements as to the interpretation of the Ownership and Operating Agreement, including, but not limited to, the rights of the co-owners to discontinue operations of, or otherwise terminate their interest in, Unit 3 and/or Unit 4. In order to address and resolve these disagreements, the owners have commenced an arbitration proceeding as provided for in the Ownership and Operating Agreement. In the course of the 2021 legislative session, the Montana Legislature passed two bills specifically directed at the ownership and operation of Colstrip. The first, Montana Senate Bill 265, purports to amend Section 27-5-323 of the Montana Code to provide that an agreement designating venue or disputes involving an electric generation facility located in Montana is not valid unless it requires arbitration in Montana before a panel of three arbitrators. The Ownership and Operating Agreement for Colstrip Units 3 & 4 includes an arbitration provision, through which all owners agreed to resolve disputes regarding the Agreement through arbitration in Spokane County, Washington before a single arbitrator. The Company, together with Puget Sound Energy, Portland General Electric, and PacifiCorp (Pacific Northwest Colstrip owners), has commenced an action in Spokane County Superior Court to compel arbitration of the pending disputes regarding interpretation of the Ownership & Operating Agreement in accordance with the requirements of the parties’ Agreement. The Pacific Northwest Colstrip owners have also commenced action in the U.S. District Court for the District of Montana to challenge the legality and constitutionality of the legislation. The Montana Legislature has also passed Montana Senate Bill 266, which would make it an unfair or deceptive act or practice, within the meaning of Montana’s Consumer Protection Act, for one or more owners of a jointly owned electrical generation facility to fail to fund its share of operating costs associated with that facility, or to engage in any conduct that would bring about a permanent closure of one or more generating units of such a facility without first obtaining the consent of all co-owners of that facility. The Company intends to challenge the legality and constitutionality of this bill as well. The Company is not able to predict the outcome, nor an amount or range of potential impact in the event of an outcome that is adverse to the Company’s interests. Other Contingencies In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes that any ultimate liability arising from these actions will not have a material impact on its financial condition, results of operations or cash flows. It is possible that a change could occur in the Company’s estimates of the probability or amount of a liability being incurred. Such a change, should it occur, could be significant. See "Note 22 of the Notes to Consolidated Financial Statements" in the 2020 Form 10-K for additional discussion regarding other contingencies.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

NOTE 15. COMMITMENTS AND CONTINGENCIES

In the course of its business, the Company becomes involved in various claims, controversies, disputes and other contingent matters, including the items described in this Note. Some of these claims, controversies, disputes and other contingent matters involve litigation or other contested proceedings. For all such matters, the Company intends to vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any particular matter because litigation and other contested proceedings are inherently subject to numerous uncertainties. For matters that affect Avista Utilities’ or AEL&P's operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process.

Boyds Fire (State of Washington Department of Natural Resources v. Avista)

In August 2019, the Company was served with a complaint, captioned “State of Washington Department of Natural Resources v. Avista Corporation,” seeking recovery up to $4.4 million for fire suppression and investigation costs and related expenses incurred in connection with a wildfire that occurred in Ferry County, Washington in August 2018. Specifically, the complaint alleges that the fire, which became known as the “Boyds Fire,” was caused by a dead ponderosa pine tree falling into an overhead distribution line, and that Avista Corp. was negligent in failing to identify and remove the tree before it came into contact with the line. Avista Corp.

disputes that the tree in question was the cause of the fire and that it was negligent in failing to identify and remove it. Additional lawsuits have subsequently been filed by private landowners seeking property damages, and holders of insurance subrogation claims seeking recovery of insurance proceeds paid.

The lawsuits were filed in the Superior Court of Ferry County, Washington and subsequently consolidated into a single action. The Company intends to vigorously defend itself in the litigation. However, the Company cannot predict the outcome of these matters.

Labor Day Windstorm

In September 2020, a severe windstorm occurred in eastern Washington and northern Idaho. The extreme weather event resulted in customer outages and the cause of multiple wildfires in the region. With respect to wildfires, the Company’s investigation determined that the primary cause of the fires was extreme high winds. To date, the Company has not found any evidence that the fires were caused by any deficiencies in its equipment, maintenance activities or vegetation management practices.

The Company has become aware of instances where, during the course of the storm, otherwise healthy trees and limbs, located in areas outside its maintenance right-of-way, broke under the extraordinary wind conditions and caused damage to its energy delivery system at or near what is believed to be the potential area of origin of a wildfire. Those instances include what has been referred to as: the Babb Road fire (near Malden and Pine City, Washington); the Christensen Road fire (near Airway Heights, Washington); and the Mile Marker 49 fire (near Orofino, Idaho). These wildfires covered, in total, approximately 22,000 acres. The Company currently estimates approximately 230 residential, commercial and other structures were impacted. Parallel investigations by applicable state agencies, including the Washington Department of Natural Resources, are ongoing, and the Company is cooperating with those efforts.

The Company’s investigation has found no evidence of negligence with respect to any of the fires, and the Company intends to vigorously defend any claims for damages that may be asserted against it with respect to the wildfires arising out of the extreme wind event.

Colstrip

The Washington CETA imposes deadlines by which coal-fired resources, such as Colstrip, must be excluded from the rate base of Washington utilities and by which electricity from such resources may no longer be delivered to Washington retail customers. Not all of the co-owners of Colstrip Units 3 & 4 are Washington utilities subject to CETA, and the co-owners have differing needs for the generating capacity of these units. Accordingly, business disagreements have arisen among the co-owners, including, but not limited to, disagreements as to the shut-down date or dates of these units. These business disagreements, in turn, have led to disagreements as to the interpretation of the Ownership and Operating Agreement, including, but not limited to, the rights of the co-owners to discontinue operations of, or otherwise terminate their interest in, Unit 3 and/or Unit 4. In order to address and resolve these disagreements, the owners have commenced an arbitration proceeding as provided for in the Ownership and Operating Agreement.

In the course of the 2021 legislative session, the Montana Legislature passed two bills specifically directed at the ownership and operation of Colstrip. The first, Montana Senate Bill 265, purports to amend Section 27-5-323 of the Montana Code to provide that an agreement designating venue or disputes involving an electric generation facility located in Montana is not valid unless it requires arbitration in Montana before a panel of three arbitrators. The Ownership and Operating Agreement for Colstrip Units 3 & 4 includes an arbitration provision, through which all owners agreed to resolve disputes regarding the Agreement through arbitration in Spokane County, Washington before a single arbitrator. The Company, together with Puget Sound Energy, Portland General Electric, and PacifiCorp (Pacific Northwest Colstrip owners), has commenced an action in Spokane County Superior Court to compel arbitration of the pending disputes regarding interpretation of the Ownership & Operating Agreement in accordance with the requirements of the parties’ Agreement. The Pacific Northwest Colstrip owners have also commenced action in the U.S. District Court for the District of Montana to challenge the legality and constitutionality of the legislation.

The Montana Legislature has also passed Montana Senate Bill 266, which would make it an unfair or deceptive act or practice, within the meaning of Montana’s Consumer Protection Act, for one or more owners of a jointly owned electrical generation facility to fail to fund its share of operating costs associated with that facility, or to engage in any conduct that would bring about a permanent closure

of one or more generating units of such a facility without first obtaining the consent of all co-owners of that facility. The Company intends to challenge the legality and constitutionality of this bill as well.

The Company is not able to predict the outcome, nor an amount or range of potential impact in the event of an outcome that is adverse to the Company’s interests.

Other Contingencies

In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes that any ultimate liability arising from these actions will not have a material impact on its financial condition, results of operations or cash flows. It is possible that a change could occur in the Company’s estimates of the probability or amount of a liability being incurred. Such a change, should it occur, could be significant. See "Note 22 of the Notes to Consolidated Financial Statements" in the 2020 Form 10-K for additional discussion regarding other contingencies.