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Long-Term Debt and Capital Leases (Narrative) (Details) - USD ($) $ in Billions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.61%	2.36%	1.81%
Avista Utilities [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount Of First Mortgage Bonds That Could Be Issued	$ 1.2
Alaska Electric Light & Power [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount Of First Mortgage Bonds That Could Be Issued	$ 0.0

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- Definition

Amount Of First Mortgage Bonds That Could Be Issued

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- Definition

Amount of First Mortgage Bonds that Could be Issued, Percent

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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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