Evaluated Power Capacity

No definition available.

Name:	ava_EvaluatedPowerCapacity
Namespace Prefix:	ava_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected Power Production

+ References

No definition available.

+ Details

Name:	ava_ExpectedPowerProduction
Namespace Prefix:	ava_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of Net Income (Loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 55

-Paragraph 4J

-URI http://asc.fasb.org/extlink&oid=35736750&loc=SL4591551-111686

+ Details

Name:	us-gaap_NetIncomeLossAttributableToNoncontrollingInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5728-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5747-111685

+ Details

Name:	us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=ava_LancasterPowerPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=ava_PalouseWindPowerPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Variable Interest Entities (Details) (USD $)	3 Months Ended								12 Months Ended
Variable Interest Entities (Details) (USD $)	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating revenues from continuing operations	$ 411,846,000us-gaap_Revenues	$ 301,558,000us-gaap_Revenues	$ 312,580,000us-gaap_Revenues	$ 446,578,000us-gaap_Revenues	$ 404,280,000us-gaap_Revenues	$ 289,477,000us-gaap_Revenues	$ 307,488,000us-gaap_Revenues	$ 440,499,000us-gaap_Revenues	$ 1,472,562,000us-gaap_Revenues	$ 1,441,744,000us-gaap_Revenues	$ 1,391,338,000us-gaap_Revenues
Noncontrolling interest	23,000	20,000	(289,000)	482,000	(134,000)	518,000	73,000	760,000
Lancaster Power Purchase Agreement [Member]
Evaluated Power Capacity									270
Future contractual obligation	323,700,000								323,700,000
Palouse Wind Power Purchase Agreement [Member]
Evaluated Power Capacity									105
Expected power production, in megawatts									40
Future contractual obligation	$ 595,600,000								$ 595,600,000
Minimum [Member] \| Lancaster Power Purchase Agreement [Member]
Minimum estimated life of plant, in years									15 years
Maximum [Member] \| Lancaster Power Purchase Agreement [Member]
Minimum estimated life of plant, in years									25 years