XML 153 R112.htm IDEA: XBRL DOCUMENT v3.8.0.1

Regulatory Matters (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended		36 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Regulated Asset Liability [Line Items]
Regulatory Assets	$ 664,149	$ 699,828
Company Share of Benefit (Expense) Under Washington Energy Recovery Mechanism	4,600	5,100
Regulatory Liabilities	(848,353)	(396,952)
Deferred natural gas costs	$ 37,474	30,820
Percent of Interest Rate Swaps Allocated to Washington	60.00%
WASHINGTON
Regulated Asset Liability [Line Items]
Decoupling Maximum Rate Increase Request	0.00%
IDAHO
Regulated Asset Liability [Line Items]
Public Utilities, Approved Return on Equity, Percentage			9.80%
Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets	$ 169,704	161,508
Power Deferrals Regulatory Asset [Member] | IDAHO
Regulated Asset Liability [Line Items]
Regulatory Liabilities	(6,100)	(2,200)
Power Deferrals [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities	(29,873)	(23,528)
Power Deferrals [Member] | WASHINGTON
Regulated Asset Liability [Line Items]
Regulatory Liabilities	(23,700)	(21,300)
Revenue Subject to Refund [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities	(5,770)	(10,297)
Revenue Subject to Refund [Member] | WASHINGTON
Regulated Asset Liability [Line Items]
Regulatory Liabilities	(3,420)	(5,113)
Revenue Subject to Refund [Member] | IDAHO
Regulated Asset Liability [Line Items]
Regulatory Liabilities	(2,350)	$ (5,184)
2016 | Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets	54,000
2017 | Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets	8,800
2018 and Beyond [Member] | Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets	$ 66,000

X

- Definition

Company Share of Benefit (Expense) Under Washington Energy Recovery Mechanism

+ References

No definition available.

+ Details

Name:	ava_CompanyShareofBenefitExpenseUnderWashingtonEnergyRecoveryMechanism
Namespace Prefix:	ava_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Decoupling Maximum Rate Increase Request

+ References

No definition available.

+ Details

Name:	ava_DecouplingMaximumRateIncreaseRequest
Namespace Prefix:	ava_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percent of Interest Rate Swaps Allocated to Washington

+ References

No definition available.

+ Details

Name:	ava_PercentofInterestRateSwapsAllocatedtoWashington
Namespace Prefix:	ava_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Regulated Asset Liability [Line Items]

+ References

No definition available.

+ Details

Name:	ava_RegulatedAssetLiabilityLineItems
Namespace Prefix:	ava_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Gas costs of a regulated entity that are refundable through future rate adjustments. Such costs are a form of a regulatory liabilities and are expected to be refunded in less than one year through rate adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

X

- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

Name:	us-gaap_RegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

+ Details

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

X

- Details

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=stpr_WA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatutoryAccountingPracticesByJurisdictionAxis=stpr_ID
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RegulatoryAssetAxis=us-gaap_DeferredDerivativeGainLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RegulatoryLiabilityAxis=ava_PowerDeferralsRegulatoryAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RegulatoryLiabilityAxis=ava_PowerDeferralsRegulatoryLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RegulatoryLiabilityAxis=us-gaap_RevenueSubjectToRefundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ava_DerivativesCashSettlementDateAxis=ava_TwoThousandSixteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ava_DerivativesCashSettlementDateAxis=ava_TwoThousandSeventeenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ava_DerivativesCashSettlementDateAxis=ava_A2018andBeyondMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: