Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Appropriated Retained Earnings [Table Text Block]

The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands):

	2016		2015
Appropriated retained earnings	$	25,564	$	21,030

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

Accumulated other comprehensive loss, net of tax, consisted of the following as of December 31 (dollars in thousands):

	2016		2015
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $4,075 and $3,580, respectively	$	7,568	$	6,650

Schedule of Goodwill [Table Text Block]

The changes in the carrying amount of goodwill are as follows (dollars in thousands):

	AEL&P			Other		Accumulated Impairment Losses			Total
Balance as of January 1, 2015	$	52,730		$	12,979	$	(7,733	)	$	57,976
Adjustments	(304		)	—		—			(304		)
Balance as of the December 31, 2015	52,426			12,979		(7,733		)	57,672
Balance as of the December 31, 2016	$	52,426		$	12,979	$	(7,733	)	$	57,672

Accumulated impairment losses are attributable to the other businesses. The goodwill adjustments recorded during 2015 relate to the final true-up of income taxes associated with the acquisition of AERC, which occurred on July 1, 2014. See Note 4 for information regarding this business acquisition and Note 21 regarding the Company's reportable segments.

Regulatory Liability For Utility Plant Retirement Costs [Table Text Block]

The Company has recorded the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and included them as a regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in thousands):

	2016		2015
Regulatory liability for utility plant retirement costs	$	273,983	$	261,594

Schedule of Inventory, Current [Table Text Block]

Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or market for our non-regulated operations and consisted of the following as of December 31 (dollars in thousands):

	2016		2015
Materials and supplies	$	40,700	$	37,101
Fuel stock	4,585		4,273
Stored natural gas	8,029		12,774
Total	$	53,314	$	54,148

Allowance for Credit Losses on Financing Receivables [Table Text Block]

The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in thousands):

	2016			2015			2014
Allowance as of the beginning of the year	$	4,530		$	4,888		$	44,309
Additions expensed during the year	6,053			5,802			5,296
Net deductions (1)	(5,557		)	(6,160		)	(44,717		)
Allowance as of the end of the year	$	5,026		$	4,530		$	4,888

(1) During 2014, the Company received $15.0 million in gross proceeds related to the settlement of its California wholesale power markets litigation. The gross proceeds effectively settled all outstanding receivables and payables at Avista Energy (which had been fully reserved against since 2001). As a result of the settlement, the Company reversed $15.0 million of the allowance, which was recorded as a reduction to non-utility other operating expenses on the Consolidated Statements of Income, and the remainder of the receivables, payables and allowance of $24.5 million were removed from the Consolidated Balance Sheets (and had no effect on net income).

Schedule of Other Nonoperating Income (Expense) [Table Text Block]

Other Income - net consisted of the following items for the years ended December 31 (dollars in thousands):

	2016			2015			2014
Interest income	$	1,823		$	653		$	987
Interest on regulatory deferrals	1,308			48			220
Equity-related AFUDC	8,475			8,331			8,808
Net gain (loss) on investments	(2,152		)	(637		)	276
Other income	624			905			1,055
Total	$	10,078		$	9,300		$	11,346

Schedule of Share-based Compensation, Activity [Table Text Block]

The following table summarizes the number of grants, vested and unvested shares, earned shares (based on market metrics), and other pertinent information related to the Company's stock compensation awards for the years ended December 31:

	2016			2015			2014
Restricted Shares
Shares granted during the year	58,610			58,302			62,075
Shares vested during the year	(52,385		)	(60,379		)	(52,899		)
Unvested shares at end of year	109,806			106,091			112,042
Unrecognized compensation expense at end of year (in thousands)	$	1,853		$	1,705		$	1,349
TSR Awards
TSR shares granted during the year	116,435			116,435			117,550
TSR shares vested during the year	(111,665		)	(171,334		)	(167,584		)
TSR shares earned based on market metrics	132,887			222,734			97,199
Unvested TSR shares at end of year	222,228			223,697			287,834
Unrecognized compensation expense (in thousands)	$	3,409		$	3,219		$	2,833
CEPS Awards
CEPS shares granted during the year	57,521			58,259			59,025
CEPS shares vested during the year	(55,835		)	—			—
CEPS shares earned based on market metrics	90,460			—			—
Unvested CEPS shares at end of year	110,452			111,887			58,017
Unrecognized compensation expense (in thousands)	$	1,671		$	1,840		$	1,577

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

The Company recorded stock-based compensation expense (included in other operating expenses) and income tax benefits in the Consolidated Statements of Income of the following amounts for the years ended December 31 (dollars in thousands):

	2016		2015		2014
Stock-based compensation expense	$	7,891	$	6,914	$	6,007
Income tax benefits (1)	4,359		2,420		2,102

Effective Rate On Allowance For Funds Used During Construction [Table Text Block]

The effective AFUDC rate was the following for the years ended December 31:

	2016		2015		2014
Avista Utilities
Effective AFUDC rate	7.29	%	7.32	%	7.64	%
Alaska Electric Light and Power Company
Effective AFUDC rate	9.40	%	9.31	%	10.37	%

Schedule Of Utilities Operating Revenue Expense Taxes [Table Text Block]

for the years ended December 31 (dollars in thousands):

	2016		2015		2014
Utility related taxes	$	57,745	$	59,173	$	58,250
Property taxes	38,505		35,948		33,932
Other taxes	2,485		2,536		2,118
Total	$	98,735	$	97,657	$	94,300

Ratio Of Depreciation To Average Depreciable Property [Table Text Block]

For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31:

	2016		2015		2014
Avista Utilities
Ratio of depreciation to average depreciable property	3.11	%	3.09	%	2.97	%
Alaska Electric Light and Power Company
Ratio of depreciation to average depreciable property	2.39	%	2.42	%	2.43	%

The average service lives for the following broad categories of utility plant in service are (in years):

	Avista Utilities	Alaska Electric Light and Power Company
Electric thermal/other production	41	41
Hydroelectric production	78	42
Electric transmission	57	41
Electric distribution	35	40
Natural gas distribution property	45	N/A
Other shorter-lived general plant	9	15

The balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands):

	2016		2015
Avista Utilities:
Electric production	$	1,346,332	$	1,217,179
Electric transmission	682,529		640,586
Electric distribution	1,525,175		1,468,157
Electric construction work-in-progress (CWIP) and other	296,912		358,846
Electric total	3,850,948		3,684,768
Natural gas underground storage	44,672		43,080
Natural gas distribution	954,298		878,982
Natural gas CWIP and other	57,601		62,024
Natural gas total	1,056,571		984,086
Common plant (including CWIP)	527,458		456,796
Total Avista Utilities	5,434,977		5,125,650
AEL&P:
Electric production	94,839		72,292
Electric transmission	20,252		18,817
Electric distribution	20,057		19,005
Electric production held under long-term capital lease	71,007		71,007
Electric CWIP and other	7,190		16,971
Electric total	213,345		198,092
Common plant	8,651		8,133
Total AEL&P	221,996		206,225
Other (1)	30,764		25,709
Total	$	5,687,737	$	5,357,584

(1) Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets. Accumulated depreciation was $11.2 million as of December 31, 2016 and $10.6 million as of December 31, 2015 for the other businesses.

Unbilled Accounts Receivable [Table Text Block]

Accounts receivable includes unbilled energy revenues of the following amounts as of December 31 (dollars in thousands):

	2016		2015
Unbilled accounts receivable	$	72,377	$	62,003

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

The following table details the reclassifications out of accumulated other comprehensive loss by component for the years ended December 31 (dollars in thousands):

	Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components	2016			2015			2014			Affected Line Item in Statement of Income
Realized gains on investment securities	$	—		$	—		$	(3	)	(a)
Realized losses on investment securities	—			—			735			(a)
	—			—			732			Total before tax
	—			—			(272		)	Tax expense (a)
	$	—		$	—		$	460		Net of tax
Amortization of defined benefit pension items
Amortization of net prior service cost	$	(1,171	)	$	31		$	(1,094	)	(b)
Amortization of net loss	(7,602		)	2,623			(83,301		)	(b)
Adjustment due to effects of regulation	7,360			(749		)	78,773			(b)
	(1,413		)	1,905			(5,622		)	Total before tax
	495			(667		)	1,967			Tax benefit (expense)
	$	(918	)	$	1,238		$	(3,655	)	Net of tax

(a) These amounts were included as part of net income from discontinued operations for all periods presented (see Note 5 for additional details).

(b) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 10 for additional details).