Committed Lines of Credit - Additional Information (Details) - USD ($)	1 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Apr. 30, 2014
Avista Utilities [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity				$ 400,000,000.0
Line of credit facility, expiration date	2026-06
Line of credit facility additional expiration period		1 year
Line of credit, current	$ 296,000,000	$ 296,000,000	$ 102,000,000
Letters of credit outstanding at end of period	24,118,000	24,118,000	27,618,000
Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	25,000,000.0	$ 25,000,000.0
Line of credit facility, expiration date		2024-11
Line of credit, current	0	$ 0	1,000,000.0
Letters of credit outstanding at end of period	$ 0	$ 0	$ 0

- Definition

The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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