Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.51%	1.29%
Secured and Unsecured Debt	$ 1,626,700	$ 1,626,700
Interest Rate, minimum	1.29%	1.11%
Interest Rate, maximum	1.51%	1.29%
Secured Debt	$ 1,611,700	$ 1,611,700
Capital Lease Obligations	67,810	68,601
Settled interest rate swaps	(26,334)	(26,515)
Unamortized debt discount	(916)	(956)
Unamortized Debt Issuance Expense	(10,572)	(10,852)
Total	1,656,688	1,656,978
Pollution Control Bonds	(83,700)	(83,700)
Long-term Debt and Capital Lease Obligations, Current	(93,197)	(93,167)
Long-term debt and capital leases	$ 1,479,791	1,480,111
Document Period End Date	Mar. 31, 2016
2018, 7.39% - 7.45% [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Interest Rate, minimum	7.39%
Interest Rate, maximum	7.45%
2023, 7.18% - 7.54% [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Interest Rate, minimum	7.18%
Interest Rate, maximum	7.54%
2032 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	$ 66,700
2034 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	17,000
Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt	$ 1,536,700	1,536,700
Avista Utilities [Member] \| 2018, 5.95% [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2018
Debt Instrument, Interest Rate, Stated Percentage	5.95%
Secured Debt	$ 250,000	250,000
Avista Utilities [Member] \| 2018, 7.39% - 7.45% [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2018
Medium-Term Notes, Noncurrent	$ 22,500	22,500
Avista Utilities [Member] \| 2019 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2019
Debt Instrument, Interest Rate, Stated Percentage	5.45%
Secured Debt	$ 90,000	90,000
Avista Utilities [Member] \| 2020 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2020
Debt Instrument, Interest Rate, Stated Percentage	3.89%
Secured Debt	$ 52,000	52,000
Avista Utilities [Member] \| 2022 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2022
Debt Instrument, Interest Rate, Stated Percentage	5.13%
Secured Debt	$ 250,000	250,000
Avista Utilities [Member] \| 2023, 7.18% - 7.54% [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2023
Medium-Term Notes, Noncurrent	$ 13,500	13,500
Avista Utilities [Member] \| 2028 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2028
Debt Instrument, Interest Rate, Stated Percentage	6.37%
Medium-Term Notes, Noncurrent	$ 25,000	25,000
Avista Utilities [Member] \| 2032 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2032
Pollution Control Bonds	$ 66,700	66,700
Avista Utilities [Member] \| 2034 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2034
Pollution Control Bonds	$ 17,000	17,000
Avista Utilities [Member] \| 2035 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2035
Debt Instrument, Interest Rate, Stated Percentage	6.25%
Secured Debt	$ 150,000	150,000
Avista Utilities [Member] \| 2037 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2037
Debt Instrument, Interest Rate, Stated Percentage	5.70%
Secured Debt	$ 150,000	150,000
Avista Utilities [Member] \| 2040 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2040
Debt Instrument, Interest Rate, Stated Percentage	5.55%
Secured Debt	$ 35,000	35,000
Avista Utilities [Member] \| 2041 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2041
Debt Instrument, Interest Rate, Stated Percentage	4.45%
Secured Debt	$ 85,000	85,000
Avista Utilities [Member] \| 2047 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2047
Debt Instrument, Interest Rate, Stated Percentage	4.23%
Secured Debt	$ 80,000	80,000
Avista Utilities [Member] \| 2016 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2016
Debt Instrument, Interest Rate, Stated Percentage	0.84%
Secured Debt	$ 90,000	90,000
Avista Utilities [Member] \| 2044 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2044
Debt Instrument, Interest Rate, Stated Percentage	4.11%
Secured Debt	$ 60,000	60,000
Avista Utilities [Member] \| 2045 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2045
Debt Instrument, Interest Rate, Stated Percentage	4.37%
Secured Debt	$ 100,000	100,000
Alaska Electric Light & Power [Member] \| 2044 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Maturity Year	2044
Debt Instrument, Interest Rate, Stated Percentage	4.54%
Secured Debt	$ 75,000	75,000
Alaska Energy Resources Company [Member] \| 2019 [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2019
Debt Instrument, Interest Rate, Stated Percentage	3.85%
Unsecured Debt	$ 15,000	$ 15,000

Long-Term Debt, Before Current Portion And Bonds Held by Company

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Settled Interest Rate Swaps

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Contractual interest rate for funds borrowed, under the debt agreement.

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Maximum contractual interest rate for funds borrowed, under the debt agreement.

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Minimum contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section H

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Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

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Noncurrent portion of a debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.

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Carrying value at the balance sheet date of the noncurrent portion of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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