Avista (AVA) 10-Q 7 May 14 2014 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Trading Symbol	'ava	'
Entity Registrant Name	'AVISTA CORP	'
Entity Central Index Key	'0000104918	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	60,169,046

Consolidated_Statements_Of_Inc

Consolidated Statements Of Income (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Common Stock, Dividends, Per Share, Cash Paid	$0.32	$0.31
Operating Revenues:	'	'
Utility revenues	$437,124	$431,127
Ecova revenues	44,384	42,407
Other non-utility revenues	9,454	9,372
Total operating revenues	490,962	482,906
Utility operating expenses:	'	'
Resource costs	220,497	229,630
Other operating expenses	67,337	65,444
Depreciation and amortization	30,726	27,935
Taxes other than income taxes	28,146	25,817
Ecova operating expenses:	'	'
Other operating expenses	37,877	35,990
Depreciation and Amortization	3,709	3,493
Other non-utility operating expenses:	'	'
Other operating expenses	9,383	9,345
Depreciation and amortization	147	190
Total operating expenses	397,822	397,844
Income from operations	93,140	85,062
Interest expense	19,084	19,692
Interest expense to affiliated trusts	111	118
Capitalized interest	-661	-940
Other income-net	-2,551	-2,145
Income before income taxes	77,157	68,337
Income tax expense	28,176	25,236
Net income	48,981	43,101
Net income attributable to noncontrolling interests	-482	-760
Net income attributable to Avista Corporation shareholders	$48,499	$42,341
Weighted-average common shares outstanding (thousands), basic	60,122	59,866
Weighted-average common shares outstanding (thousands), diluted	60,168	59,898
Earnings per common share attributable to Avista Corporation shareholders:	'	'
Basic (usd per share)	$0.81	$0.71
Diluted (usd per share)	$0.81	$0.71

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]	'	'
Net income	$48,981	$43,101
Other Comprehensive Income (Loss):	'	'
Unrealized investment gains/(losses) - net of taxes	785	-70
Reclassification adjustment for realized gains on investment securities included in net income - net of taxes	-2	-1
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes	111	184
Total other comprehensive loss	894	113
Comprehensive income	49,875	43,214
Comprehensive income attributable to noncontrolling interests	-482	-760
Comprehensive income attributable to Avista Corporation shareholders	$49,393	$42,454

Consolidated_Statements_Of_Com1

Consolidated Statements Of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]	'	'
Unrealized investment gains - taxes	$463	($39)
Realized investment gains - taxes	-1	-1
Change in unfunded benefit obligation for pension and other postretirement benefit plans - taxes	$59	$99

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets:	'	'
Cash and cash equivalents	$90,172	$82,574
Accounts and notes receivable-less allowances of $44,598 and $44,309, respectively	202,820	221,343
Utility energy commodity derivative assets	13,925	3,022
Regulatory asset for utility derivatives	0	10,829
Investments and funds held for clients	95,851	96,688
Materials and supplies, fuel stock and natural gas stored	32,804	44,946
Deferred income taxes	24,288	24,788
Income taxes receivable	0	7,783
Other current assets	44,526	57,706
Total current assets	504,386	549,679
Net Utility Property:	'	'
Utility plant in service	4,341,383	4,290,464
Construction work in progress	157,330	160,323
Total	4,498,713	4,450,787
Less: Accumulated depreciation and amortization	1,271,082	1,248,362
Total net utility property	3,227,631	3,202,425
Other Non-current Assets:	'	'
Investment in exchange power-net	13,271	13,883
Investment in affiliated trusts	11,547	11,547
Goodwill	76,257	76,257
Intangible assets-net of accumulated amortization of $39,410 and $36,634, respectively	38,610	39,576
Long-term energy contract receivable of Spokane Energy	37,612	40,619
Other property and investments-net	48,171	58,555
Total other non-current assets	225,468	240,437
Deferred Charges:	'	'
Regulatory assets for deferred income tax	69,084	71,421
Regulatory assets for pensions and other postretirement benefits	155,205	156,984
Other regulatory assets	105,807	102,915
Non-current utility energy commodity derivative assets	3,545	854
Non-current regulatory asset for utility derivatives	11,654	23,258
Other deferred charges	13,298	13,950
Total deferred charges	358,593	369,382
Total assets	4,316,078	4,361,923
Current Liabilities:	'	'
Accounts payable	163,655	182,088
Client fund obligations	97,128	99,117
Current portion of long-term debt	372	358
Current portion of nonrecourse long-term debt of Spokane Energy	13,872	16,407
Short-term borrowings	111,000	171,000
Utility energy commodity derivative liabilities	3,360	10,875
Other current liabilities	180,834	145,495
Total current liabilities	570,221	625,340
Long-term debt	1,272,530	1,272,425
Nonrecourse long-term debt of Spokane Energy	0	1,431
Long-term debt to affiliated trusts	51,547	51,547
Long-term borrowings under committed line of credit	42,000	46,000
Regulatory liability for utility plant retirement costs	245,456	242,850
Pensions and other postretirement benefits	113,416	122,513
Deferred income taxes	534,540	535,343
Other non-current liabilities and deferred credits	119,295	130,318
Total liabilities	2,949,005	3,027,767
Commitments and Contingencies (See Notes to Consolidated Financial Statements)	'	'
Redeemable Noncontrolling Interests	15,960	15,889
Avista Corporation Stockholders’ Equity:	'	'
Common stock, no par value; 200,000,000 shares authorized; 60,161,140 and 60,076,752 shares outstanding, respectively	899,037	896,993
Accumulated other comprehensive loss	-4,925	-5,819
Retained earnings	436,370	407,092
Total Avista Corporation stockholders’ equity	1,330,482	1,298,266
Noncontrolling Interests	20,631	20,001
Total equity	1,351,113	1,318,267
Total liabilities and equity	$4,316,078	$4,361,923

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Accounts and notes receivable, allowances	$44,598	$44,309
Accumulated Amortization	$39,410	$36,634
Common stock, par value	$0	$0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares outstanding	60,161,140	60,076,752

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Operating Activities:	'	'
Net income	$48,981	$43,101
Non-cash items included in net income:	'	'
Depreciation and amortization	34,582	31,618
Provision for deferred income taxes	1,453	1,120
Power and natural gas cost amortizations (deferrals), net	-8,041	2,545
Amortization of debt expense	953	947
Amortization of investment in exchange power	613	613
Stock-based compensation expense	1,551	1,464
Equity-related AFUDC	-2,034	-1,391
Pension and other postretirement benefit expense	7,415	10,949
Amortization of Spokane Energy contract	3,007	2,764
Other	4,212	1,118
Contributions to defined benefit pension plan	-11,000	-14,670
Changes in working capital components:	'	'
Accounts and notes receivable	17,257	2,432
Materials and supplies, fuel stock and natural gas stored	12,141	17,137
Other current assets	30,333	-14,288
Accounts payable	-11,065	-20,778
Other current liabilities	26,540	40,698
Net cash provided by operating activities	156,898	105,379
Investing Activities:	'	'
Utility property capital expenditures (excluding equity-related AFUDC)	-59,725	-70,645
Other capital expenditures	-3,929	-819
Federal grant payments received	876	1,567
Decrease (increase) In Money Market Funds Held For Clients	-9,346	2,816
Purchase of securities available for sale	0	-24,956
Sale and maturity of securities available for sale	11,403	7,000
Other	24	-1,649
Net cash used in investing activities	-60,697	-86,686
Financing Activities:	'	'
Net increase (decrease) in short-term borrowings	-60,000	500
Borrowings from Ecova line of credit	0	3,000
Repayment of borrowings from Ecova line of credit	-4,000	-3,000
Redemption and maturity of long-term debt	-69	-101
Maturity of nonrecourse long-term debt of Spokane Energy	-3,966	-3,622
Issuance of common stock	638	1,149
Cash dividends paid	-19,217	-18,384
Increase (decrease) in client fund obligations	-1,989	15,399
Other	0	99
Net cash used in financing activities	-88,603	-4,960
Net increase in cash and cash equivalents	7,598	13,733
Cash and cash equivalents at beginning of period	82,574	75,464
Cash and cash equivalents at end of period	90,172	89,197
Cash paid during the year:	'	'
Interest	8,107	7,391
Income taxes	-99	-1,329
Non-cash financing and investing activities:	'	'
Accounts payable for capital expenditures	5,168	4,730
Redeemable noncontrolling interests	$3	$2,870

Consolidated_Statements_Of_Equ

Consolidated Statements Of Equity And Redeemable Noncontrolling Interests (USD $)	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]
In Thousands, except Share data
Beginning Balance at Dec. 31, 2012	'	$889,237	($6,700)	$376,940	$17,658	$4,938
Beginning Balance (in shares) at Dec. 31, 2012	'	59,812,796	'	'	'	'
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable	'	'	'	'	'	27
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable	'	'	'	'	733	'
Issuance of common stock	'	99,291	'	'	'	'
Equity compensation expense	'	1,461	'	'	'	'
Issuance of common stock, net of issuance costs	'	1,149	'	'	'	'
Equity transactions of consolidated subsidiaries	'	-88	'	'	'	'
Other comprehensive loss	113	'	113	'	'	'
Net income attributable to Avista Corporation shareholders	42,341	'	'	42,341	'	'
Cash dividends paid (common stock)	'	'	'	-18,384	'	'
Total equity	1,304,738	'	'	'	'	'
Other	'	'	'	'	2,371	'
Purchase of subsidiary noncontrolling interests	'	'	'	'	'	0
Valuation adjustments and other noncontrolling interests activity	'	'	'	-2,093	'	3,005
Ending Balance at Mar. 31, 2013	1,283,976	891,759	-6,587	398,804	20,762	7,970
Ending Balance (in shares) at Mar. 31, 2013	'	59,912,087	'	'	'	'
Beginning Balance at Dec. 31, 2013	1,298,266	896,993	-5,819	407,092	20,001	15,889
Beginning Balance (in shares) at Dec. 31, 2013	60,076,752	60,076,752	'	'	'	'
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable	'	'	'	'	'	24
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable	'	'	'	'	458	'
Issuance of common stock	'	84,388	'	'	'	'
Equity compensation expense	'	1,619	'	'	'	'
Issuance of common stock, net of issuance costs	'	638	'	'	'	'
Equity transactions of consolidated subsidiaries	'	-213	'	'	'	'
Other comprehensive loss	894	'	894	'	'	'
Net income attributable to Avista Corporation shareholders	48,499	'	'	48,499	'	'
Cash dividends paid (common stock)	'	'	'	-19,217	'	'
Total equity	1,351,113	'	'	'	'	'
Other	'	'	'	'	172	'
Purchase of subsidiary noncontrolling interests	'	'	'	'	'	-3
Valuation adjustments and other noncontrolling interests activity	'	'	'	-4	'	50
Ending Balance at Mar. 31, 2014	$1,330,482	$899,037	($4,925)	$436,370	$20,631	$15,960
Ending Balance (in shares) at Mar. 31, 2014	60,161,140	60,161,140	'	'	'	'

Summary_Of_Significant_Account

Summary Of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Summary Of Significant Accounting Policies	'
	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Nature of Business
	Avista Corporation is an energy company engaged in the generation, transmission and distribution of electricity and distribution of natural gas, as well as other energy-related businesses. Avista Utilities is an operating division of Avista Corp., comprising the regulated utility operations. Avista Utilities provides electric distribution and transmission, as well as natural gas distribution, services in parts of eastern Washington and northern Idaho. Avista Utilities also provides natural gas distribution service in parts of northeastern and southwestern Oregon. Avista Utilities has generating facilities in Washington, Idaho, Oregon and Montana. The Company also supplies electricity to a small number of customers in Montana, most of whom are employees who operate one of the Montana generating facilities. Avista Capital, Inc. (Avista Capital), a wholly owned subsidiary of Avista Corp., is the parent company of all of the subsidiary companies in the non-utility businesses, except Spokane Energy, LLC (Spokane Energy). Avista Capital’s subsidiaries include Ecova, Inc. (Ecova), an 80.2 percent owned subsidiary as of March 31, 2014. Ecova is a provider of energy efficiency and other facility information and cost management programs and services for multi-site customers and utilities throughout North America. See Note 12 for business segment information.
	Basis of Reporting
	The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries, including Ecova and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants.
	Taxes Other Than Income Taxes
	Taxes other than income taxes include state excise taxes, city occupational and franchise taxes, real and personal property taxes and certain other taxes not based on net income. These taxes are generally based on revenues or the value of property. Utility related taxes collected from customers (primarily state excise taxes and city utility taxes) are recorded as operating revenue and expense and totaled the following amounts for the three months ended March 31 (dollars in thousands):
		2014				2013
	Utility taxes	$	19,738			$	17,906
	Other Income-Net
	Other Income-net consisted of the following items for the three months ended March 31 (dollars in thousands):
		2014				2013
	Interest income	$	(274	)		$	(258	)
	Interest income on regulatory deferrals	(44		)		(13		)
	Equity-related AFUDC	(2,034		)		(1,391		)
	Net loss on investments	40				398
	Other income	(239		)		(881		)
	Total	$	(2,551	)		$	(2,145	)
	Materials and Supplies, Fuel Stock and Natural Gas Stored
	Inventories of materials and supplies, fuel stock and natural gas stored 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 March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Materials and supplies	$	29,158			$	28,747
	Fuel stock	3,639				3,170
	Natural gas stored	7				13,029
	Total	$	32,804			$	44,946
	Investments and Funds Held for Clients and Client Fund Obligations
	In connection with the bill paying services, Ecova collects funds from its clients and remits the funds to the appropriate utility or other service provider. Some of the funds collected are invested by Ecova and classified as investments and funds held for clients, and a related liability for client fund obligations is recorded. Investments and funds held for clients include cash and cash equivalent investments, money market funds and investment securities classified as available for sale. Ecova does not invest the funds directly for the clients' benefit; therefore, Ecova bears the risk of loss associated with the investments. Investments and funds held for clients as of March 31, 2014 are as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	13,618			$	—			$	13,618
	Money market funds	23,034				—				23,034
	Securities available for sale:
	U.S. government agency	55,638				(1,311		)		54,327
	Municipal	3,086				23				3,109
	Corporate fixed income – industrial	752				11				763
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	60,476				(1,277		)		59,199
	Total investments and funds held for clients	$	97,128			$	(1,277	)		$	95,851
	Investments and funds held for clients as of December 31, 2013 are as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	16,147			$	—			$	16,147
	Money market funds	11,180				—				11,180
	Securities available for sale:
	U.S. government agency	63,633				(2,555		)		61,078
	Municipal	3,497				21				3,518
	Corporate fixed income – financial	3,000				—				3,000
	Corporate fixed income – industrial	753				12				765
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	71,883				(2,522		)		69,361
	Total investments and funds held for clients	$	99,210			$	(2,522	)		$	96,688
	-1	Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.
	Investments and funds held for clients are classified as a current asset since these funds are held for the purpose of satisfying the client fund obligations. As of March 31, 2014 and December 31, 2013, approximately 94 percent and 95 percent of the investment portfolio, respectively, were rated AA-, Aa3 and higher by nationally recognized statistical rating organizations. All fixed income securities were rated as investment grade as of March 31, 2014 and December 31, 2013.
	Ecova management reviews its investments continuously for indicators of other-than-temporary impairment. To make this determination, management employs a methodology that considers available quantitative and qualitative evidence in evaluating potential impairment of its investments. If the cost of an investment exceeds its fair value, management evaluates, among other factors, general market conditions, credit quality of instrument issuers, the length of time and extent to which the fair value is less than cost, and whether it has plans to sell the security or it is more-likely-than not that the Company will be required to sell the security before recovery. Management also considers specific adverse conditions related to the financial health of and specific prospects for the issuer as well as other cash flow factors. Once a decline in fair value is determined to be other-than-temporary, an impairment charge is recorded in earnings and a new cost basis in the investment is established. Based on management’s analysis, securities available for sale do not meet the criteria for other-than-temporary impairment as of March 31, 2014 or December 31, 2013.
	The following is a summary of the disposition of available-for-sale securities for the three months ended March 31 (dollars in thousands):
		2014				2013
	Proceeds from sales, maturities and calls	$	11,403			$	7,000
	Gross realized gains	3				2
	Gross realized losses	—				—
	Contractual maturities of securities available for sale as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Due within 1 year				After 1 but within 5 years				After 5 but within 10 years			After 10 years		Total
	31-Mar-14	$	2,235			$	10,508			$	43,460		$	2,996	$	59,199
31-Dec-13	5,382				12,745				48,310			2,924		69,361
Actual maturities may differ due to call or prepayment rights and the effective maturity was 2.9 years as of March 31, 2014 and 3.0 years as of December 31, 2013.
Goodwill
Goodwill arising from acquisitions represents the excess of the purchase price over the estimated fair value of net assets acquired. The Company evaluates goodwill for impairment using a combination of the discounted cash flow model and a market approach on at least an annual basis or more frequently if impairment indicators arise. The Company completed its annual evaluation of goodwill for potential impairment as of December 31, 2013 for Ecova and as of November 30, 2013 for the other businesses and determined that goodwill was not impaired at that time.
The carrying amount of goodwill as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
	Ecova				Other				Accumulated			Total
									Impairment
									Losses
31-Mar-14	$	71,011			$	12,979			$	(7,733	)	$	76,257
31-Dec-13	$	71,011			$	12,979			$	(7,733	)	$	76,257
There have been no acquisitions or adjustments to goodwill during the three months ended March 31, 2014. Accumulated impairment losses are attributable to the other businesses.
Intangible Assets
Amortization expense related to Intangible Assets was as follows for the three months ended March 31 (dollars in thousands):
	2014				2013
Intangible asset amortization	$	2,776			$	2,579
The following table details the estimated amortization expense related to Intangible Assets for each of the next five years ending December 31 (dollars in thousands):
	Remaining
	2014				2015				2016			2017		2018
Estimated amortization expense	$	7,863			$	8,818			$	7,697		$	6,887	$	4,100
The gross carrying amount and accumulated amortization of Intangible Assets as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
	Estimated		March 31,				December 31,
	Useful Lives		2014				2013
Client relationships	2 - 12 years		$	33,562			$	33,562
Software development costs	3 - 7 years		41,146				39,327
Other	1 - 10 years		3,312				3,321
Total intangible assets			78,020				76,210
Client relationships accumulated amortization			(13,347		)		(12,336		)
Software development costs accumulated amortization			(23,437		)		(21,861		)
Other accumulated amortization			(2,626		)		(2,437		)
Total accumulated amortization			(39,410		)		(36,634		)
Total intangible assets - net			$	38,610			$	39,576
As of March 31, 2014 and December 31, 2013, all of the intangible assets reported above are associated with Ecova.
Derivative Assets and Liabilities
Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. In certain defined conditions, a derivative may be specifically designated as a hedge for a particular exposure. The accounting for a derivative depends on the intended use of such derivative and the resulting designation.
The Washington Utilities and Transportation Commission (UTC) and the Idaho Public Utilities Commission (IPUC) issued accounting orders authorizing Avista Utilities to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Utilities to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the Energy Recovery Mechanism (ERM) in Washington, the Power Cost Adjustment (PCA) mechanism in Idaho, and periodic general rates cases. Regulatory assets are assessed regularly and are probable for recovery through future rates.
Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts that are not considered derivatives are accounted for on the accrual basis until they are settled or realized, unless there is a decline in the fair value of the contract that is determined to be other-than-temporary.
Fair Value Measurements
Fair value represents the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Energy commodity derivative assets and liabilities, investments and funds held for clients, deferred compensation assets, as well as derivatives related to interest rate swap agreements and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 9 for the Company’s fair value disclosures.
Regulatory Deferred Charges and Credits
The Company prepares its condensed consolidated financial statements in accordance with regulatory accounting practices because:
•	rates for regulated services are established by or subject to approval by independent third-party regulators,
•	the regulated rates are designed to recover the cost of providing the regulated services, and
•	in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs.
Regulatory accounting practices require that certain costs and/or obligations (such as incurred power and natural gas costs not currently included in rates, but expected to be recovered or refunded in the future) are reflected as deferred charges or credits on the Condensed Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Condensed Consolidated Statements of Income until the period during which matching revenues are recognized. If at some point in the future the Company determines that it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be:
•	required to write off its regulatory assets, and
•	precluded from the future deferral of costs not recovered through rates at the time such costs are incurred, even if the Company expected to recover such costs in the future.
Redeemable Noncontrolling Interests
Certain option holders of Ecova have the right to put their shares back to Ecova at their discretion during an annual put window. Stock options and other outstanding redeemable stock are valued at their maximum redemption amount which is equal to their intrinsic value (fair value less exercise price).
Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss, net of tax, consisted of the following as of March 31, 2014 and December 31, 2013 (dollars in thousands):
	March 31,				December 31,
	2014				2013
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $(2,220) and $(2,280), respectively	$	(4,122	)		$	(4,233	)
Unrealized loss on securities available for sale - net of taxes of $(474) and $(936), respectively	(803		)		(1,586		)
Total accumulated other comprehensive loss	$	(4,925	)		$	(5,819	)
The following table details the reclassifications out of accumulated other comprehensive loss by component for the three months ended March 31 (dollars in thousands):
		Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components		2014				2013				Affected Line Item in Statement of Income
Realized gains on investment securities		$	3			$	2			Other income-net
		3				2				Total before tax
		(1		)		(1		)		Tax expense
		$	2			$	1			Net of tax
Amortization of defined benefit pension items
Amortization of net loss		$	(1,952	)		$	(4,891	)		(a)
Adjustment due to effects of regulation		1,782				4,608				(a)
		(170		)		(283		)		Total before tax
		59				99				Tax benefit
		$	(111	)		$	(184	)		Net of tax
(a)	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).
Appropriated Retained Earnings
In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for any earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. The rate of return on investment is specified in the various hydroelectric licensing agreements for the Clark Fork River and Spokane River. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company calculates the earnings in excess of the specified rate of return on an annual basis. The appropriated retained earnings amounts included in retained earnings were as follows as of March 31, 2014 and December 31, 2013 (dollars in thousands):
	March 31,				December 31,
	2014				2013
Appropriated retained earnings	$	9,714			$	9,714
Dividends
The payment of dividends on common stock could be limited by:
•	certain covenants applicable to preferred stock (when outstanding) contained in the Company’s Restated Articles of Incorporation, as amended (currently there are no preferred shares outstanding),
•	certain covenants applicable to the Company's outstanding long-term debt and committed line of credit agreements, and
•	the hydroelectric licensing requirements of section 10(d) of the FPA.
Under the covenant applicable to the Company's committed line of credit agreement, which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” to be greater than 65 percent at any time, the amount of retained earnings available for dividends at March 31, 2014 was limited to approximately $342.9 million.
Contingencies
The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable that a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses losses that do not meet these conditions for accrual, if there is a reasonable possibility that a loss may be incurred.

New_Accounting_Standards

New Accounting Standards	3 Months Ended
	Mar. 31, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
New Accounting Standards	'
	NEW ACCOUNTING STANDARDS
	There are no accounting standards that were recently issued that impact the Company during 2014. The Company will continue to evaluate all new accounting standards as they are issued to determine if they impact the Company's financial condition, results of operations and cash flows.

Variable_Interest_Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2014
Variable Interest Entities [Abstract]	'
Variable Interest Entities	'
	VARIABLE INTEREST ENTITIES
	Lancaster Power Purchase Agreement
	The Company has a power purchase agreement (PPA) for the purchase of all the output of the Lancaster Plant, a 270 MW natural gas-fired combined cycle combustion turbine plant located in Idaho, owned by an unrelated third-party (Rathdrum Power LLC), through 2026.
	Avista Corp. has a variable interest in the PPA. Accordingly, Avista Corp. made an evaluation of which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and which interest holders have the obligation to absorb losses or receive benefits that could be significant to the entity. Avista Corp. pays a fixed capacity and operations and maintenance payment and certain monthly variable costs under the PPA. Under the terms of the PPA, Avista Corp. makes the dispatch decisions, provides all natural gas fuel and receives all of the electric energy output from the Lancaster Plant. However, Rathdrum Power LLC (the owner) controls the daily operation of the Lancaster Plant and makes operating and maintenance decisions. Rathdrum Power LLC controls all of the rights and obligations of the Lancaster Plant after the expiration of the PPA in 2026. It is estimated that the plant will have 15 to 25 years of useful life after that time. Rathdrum Power LLC bears the maintenance risk of the plant and will receive the residual value of the Lancaster Plant. Avista Corp. has no debt or equity investments in the Lancaster Plant and does not provide financial support through liquidity arrangements or other commitments (other than the PPA). Based on its analysis, Avista Corp. does not consider itself to be the primary beneficiary of the Lancaster Plant. Accordingly, neither the Lancaster Plant nor Rathdrum Power LLC is included in Avista Corp.’s condensed consolidated financial statements. The Company has a future contractual obligation of approximately $292 million under the PPA (representing the fixed capacity and operations and maintenance payments through 2026) and believes this would be its maximum exposure to loss. However, the Company believes that such costs will be recovered through retail rates.
	Palouse Wind Power Purchase Agreement
	In June 2011, the Company entered into a 30-year PPA with Palouse Wind, LLC (Palouse Wind), an affiliate of First Wind Holdings, LLC. The PPA relates to a wind project that was developed by Palouse Wind in Whitman County, Washington and under the terms of the PPA, the Company acquires all of the power and renewable attributes produced by the wind project for a fixed price per MWh, which escalates annually, without consideration for market fluctuations. The wind project has a nameplate capacity of approximately 105 MW and is expected to produce approximately 40 aMW annually. The project was completed and energy deliveries began during the fourth quarter of 2012. Under the PPA, the Company has an annual option to purchase the wind project following the 10th anniversary of the commercial operation date at a fixed price determined under the contract.
	The Company evaluated this agreement to determine if it has a variable interest which must be consolidated. Based on its analysis, Avista Corp. does not consider itself to be the primary beneficiary of the Palouse Wind facility due to the fact that it pays a fixed price per MWh, which represents the only financial obligation, and does not have any input into the management of the day-to-day operations of the facility. Accordingly, Palouse Wind is not included in Avista Corp.’s condensed consolidated financial statements. The Company has a future contractual obligation of approximately $600 million under the PPA (representing the charges associated with purchasing the energy and renewable attributes through 2042) and believes this would be its maximum exposure to loss. However, the Company believes that such costs will be recovered through retail rates.

Business_Acquisitions

Business Acquisitions	3 Months Ended
	Mar. 31, 2014
Business Acquisitions [Abstract]	'
Business Combination Disclosure [Text Block]	'
	BUSINESS ACQUISITIONS
	Alaska Energy and Resources Company - Avista Corporation
	On November 4, 2013, the Company entered into an agreement and plan of merger (Merger Agreement) with Alaska Energy and Resources Company (AERC), a privately-held company based in Juneau, Alaska. If all necessary approvals are received, when the transaction is complete, AERC will become a wholly-owned subsidiary of Avista Corp.
	The primary subsidiary of AERC is Alaska Electric Light & Power Company (AEL&P), a regulated utility which provides electric services to approximately 16,000 customers in the City and Borough of Juneau, Alaska. In 2013, AEL&P had annual revenues of $42.6 million, a total rate base of $109 million and had 60 full-time employees. The utility has a firm retail peak load of approximately 68 MW. AEL&P owns four hydroelectric generating facilities, having a total present capacity of 24.7 MW, and has a power purchase commitment for the output of the Snettisham hydroelectric project, having a present capacity of 78 MW, for a total hydroelectric capacity of 102.7 MW. AEL&P is not interconnected to any other electric system. The utility also has 93.9 MW of diesel generating capacity to provide back-up service to firm customers when necessary.
	In addition to the regulated utility, AERC owns the AJT Mining subsidiary, which is an inactive mining company holding certain properties.
	The merger consideration at closing will be $170 million, less AERC's indebtedness and is subject to other customary closing adjustments (Merger Consideration). The transaction will be funded primarily through the issuance of Avista Corp. common stock to the shareholders of AERC. The transaction is expected to close by July 1, 2014, following the receipt of necessary regulatory approvals, the approval of the merger transaction by the requisite number of AERC shareholders and the satisfaction of other closing conditions. Avista Corp. shareholder approval is not required.
	Pursuant to the Merger Agreement, among other things, each of the issued and outstanding shares of AERC common stock (other than Dissenting Shares) will be converted into the right to receive consideration as follows:
	i.	the number of shares of Avista Corp. common stock equal to one share of AERC common stock multiplied by the Exchange Ratio; and
	ii.	a portion of the Representative Reimbursement Amount.
	For purposes of the foregoing:
	The Exchange Ratio is the ratio obtained by dividing the Per Share Amount by (i) $21.48 if the Avista Corp. Closing Price is less than or equal to $21.48, (ii) the Avista Corp. Closing Price, if the Avista Corp. Closing Price is greater than $21.48 and less than $34.30 or (iii) $34.30 if the Avista Corp. Closing Price is greater than or equal to $34.30.
	The Per Share Amount is the amount determined by dividing (a) the Merger Consideration (as adjusted) by (b) the aggregate number of shares of AERC common stock outstanding immediately prior to the closing of the transaction.
	The Representative Reimbursement Amount is a $500,000 cash payment to be made by Avista Corp. at the Closing to the Shareholders’ Representative account. The purpose of the Representative Reimbursement Amount is to reimburse the Shareholders’ Representative for expenses incurred by the Shareholders’ Representative in acting for the current shareholders of AERC in connection with the Merger. The total Merger Consideration will be reduced by the Representative Reimbursement Amount.
	Dissenting Shares will not be converted into, or represent the right to receive, the Merger Consideration or any portion of the Representative Reimbursement Amount. Such shareholders will be entitled to receive payment of the fair value of Dissenting Shares held by them in accordance with the provisions of AS 10.06.580 of the Alaska Corporations Code. Any amounts paid to Dissenting Shares over the amounts otherwise payable in the form of Merger Consideration are indemnified expenses owed by AERC to Avista Corp.
	The Merger Agreement has been approved by Avista Corp.'s and AERC's Boards of Directors, the UTC, the IPUC, the Public Utility Commission of Oregon (OPUC), the U.S. Federal Trade Commission and the Antitrust Division of the U.S. Department of Justice, but the consummation of the transaction is subject to the satisfaction or waiver of specified closing conditions, including:
	•	the registration under the Securities Act of 1933 of the shares of common stock that will be issued to AERC shareholders;
	•	the approval of such shares for listing on the New York Stock Exchange;
	•	the approval of the merger transaction by the requisite number of AERC shareholders;
	•	the receipt of regulatory approvals and other consents required to consummate the merger transaction, including, among others, approvals from the Regulatory Commission of Alaska and any other applicable regulatory bodies on the terms and conditions specified in the definitive purchase agreement;
	•	the absence of the occurrence of a material adverse effect (as defined in the Merger Agreement) relating to either AERC or Avista Corp. after the date of the signed agreement; and
	•	other customary closing conditions.
	The Merger Agreement also provides for customary termination rights for each of the Company and AERC, including the right for either party to terminate if the Merger has not been consummated by December 31, 2014, provided, however, that the failure of the Merger to have been consummated on or before December 31, 2014 was not caused by the failure of such party or any affiliate of such party to perform any of its obligations under the Merger Agreement. Upon termination of the Merger Agreement in accordance with its terms, there will be no further liability under the agreement except that nothing shall relieve any party thereto from liability for any breach of the agreement.
	There may be certain commitments and contingencies that will be assumed when the merger transaction is consummated; however, Avista Corp. has not fully completed its evaluation of all the potential commitments and contingencies as of the date of this filing.
	During the three months ended March 31, 2014, Avista Corp. incurred $0.5 million (pre-tax) of transaction related fees which have been expensed and presented in the Condensed Consolidated Statements of Income in other operating expenses within utility operating expenses. Since the start of the planned transaction through March 31, 2014, Avista Corp. has expensed $2.1 million (pre-tax) in total transaction fees associated with the transaction and Avista Corp. expects to incur additional transaction related fees upon consummation of the transaction.

Derivatives_And_Risk_Managemen

Derivatives And Risk Management	3 Months Ended
	Mar. 31, 2014
Derivative Instruments and Hedges, Assets [Abstract]	'
Derivatives And Risk Management	'
	DERIVATIVES AND RISK MANAGEMENT
	Energy Commodity Derivatives
	Avista Utilities is exposed to market risks relating to changes in electricity and natural gas commodity prices and certain other fuel prices. Market risk is, in general, the risk of fluctuation in the market price of the commodity being traded and is influenced primarily by supply and demand. Market risk includes the fluctuation in the market price of associated derivative commodity instruments. Avista Utilities utilizes derivative instruments, such as forwards, futures, swaps and options in order to manage the various risks relating to these commodity price exposures. The Company has an energy resources risk policy and control procedures to manage these risks. The Company’s Risk Management Committee establishes the Company’s energy resources risk policy and monitors compliance. The Risk Management Committee is comprised of certain Company officers and other members of management. The Audit Committee of the Company’s Board of Directors periodically reviews and discusses enterprise risk management processes, and it focuses on the Company’s material financial and accounting risk exposures and the steps management has undertaken to control them.
	As part of the Company's resource procurement and management operations in the electric business, the Company engages in an ongoing process of resource optimization, which involves the economic selection from available energy resources to serve the Company's load obligations and the use of these resources to capture available economic value. The Company transacts in wholesale markets by selling and purchasing electric capacity and energy, fuel for electric generation, and derivative contracts related to capacity, energy and fuel. Such transactions are part of the process of matching resources with load obligations and hedging the related financial risks. These transactions range from terms of intra-hour up to multiple years.
	Avista Utilities makes continuing projections of:
	•	electric loads at various points in time (ranging from intra-hour to multiple years) based on, among other things, estimates of customer usage and weather, historical data and contract terms, and
	•	resource availability at these points in time based on, among other things, fuel choices and fuel markets, estimates of streamflows, availability of generating units, historic and forward market information, contract terms, and experience.
	On the basis of these projections, the Company makes purchases and sales of electric capacity and energy, fuel for electric generation, and related derivative instruments to match expected resources to expected electric load requirements and reduce exposure to electricity (or fuel) market price changes. Resource optimization involves generating plant dispatch and scheduling available resources and also includes transactions such as:
	•	purchasing fuel for generation,
	•	when economical, selling fuel and substituting wholesale electric purchases, and
	•	other wholesale transactions to capture the value of generation and transmission resources and fuel delivery capacity contracts.
	Avista Utilities’ optimization process includes entering into hedging transactions to manage risks. Transactions include both physical energy contracts and related derivative financial instruments.
	As part of its resource procurement and management of its natural gas business, Avista Utilities makes continuing projections of its natural gas loads and assesses available natural gas resources including natural gas storage availability. Natural gas resource planning typically includes peak requirements, low and average monthly requirements and delivery constraints from natural gas supply locations to Avista Utilities’ distribution system. However, daily variations in natural gas demand can be significantly different than monthly demand projections. On the basis of these projections, Avista Utilities plans and executes a series of transactions to hedge a significant portion of its projected natural gas requirements through forward market transactions and derivative instruments. These transactions may extend as much as four natural gas operating years (November through October) into the future. Avista Utilities also leaves a significant portion of its natural gas supply requirements unhedged for purchase in short-term and spot markets.
	Natural gas resource optimization activities include:
	•	wholesale market sales of surplus natural gas supplies,
	•	optimization of interstate pipeline transportation capacity not needed to serve daily load, and
	•	purchases and sales of natural gas to optimize use of storage capacity.
	The following table presents the underlying energy commodity derivative volumes as of March 31, 2014 that are expected to be delivered in each respective year (in thousands of MWhs and mmBTUs):
		Purchases										Sales
		Electric Derivatives					Gas Derivatives					Electric Derivatives					Gas Derivatives
	Year	Physical (1)		Financial (1)			Physical (1)			Financial (1)		Physical (1)		Financial (1)			Physical (1)			Financial (1)
		MWH		MWH			mmBTUs			mmBTUs		MWH		MWH			mmBTUs			mmBTUs
	2014	725		1,768			18,282			110,762		688		2,522			3,021			87,043
	2015	559		1,461			4,973			82,825		222		2,566			1,490			58,210
	2016	397		948			2,505			51,950		256		1,634			910			41,490
	2017	397		—			675			—		286		—			—			—
	2018	397		—			—			—		286		—			—			—
	Thereafter	235		—			—			—		158		—			—			—
	-1	Physical transactions represent commodity transactions where Avista Utilities will take delivery of either electricity or natural gas and financial transactions represent derivative instruments with no physical delivery, such as futures, swaps or options.
	The electric and natural gas derivative contracts above will be included in either power supply costs or natural gas supply costs during the period they are delivered and will be included in the various recovery mechanisms (ERM, PCA, and PGAs), or in the general rate case process, and are expected to be collected through retail rates from customers.
	Foreign Currency Exchange Contracts
	A significant portion of Avista Utilities’ natural gas supply (including fuel for power generation) is obtained from Canadian sources. Most of those transactions are executed in U.S. dollars, which avoids foreign currency risk. A portion of Avista Utilities’ short-term natural gas transactions and long-term Canadian transportation contracts are committed based on Canadian currency prices and settled within sixty days with U.S. dollars. Avista Utilities hedges a portion of the foreign currency risk by purchasing Canadian currency contracts when such commodity transactions are initiated. This risk has not had a material effect on the Company’s financial condition, results of operations or cash flows and these differences in cost related to currency fluctuations were included with natural gas supply costs for ratemaking.
	The following table summarizes the foreign currency hedges that the Company has entered into as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,			December 31,
		2014			2013
	Number of contracts	23			23
	Notional amount (in United States dollars)	$	13,128		$	8,631
	Notional amount (in Canadian dollars)	14,596			9,191
	Interest Rate Swap Agreements
	Avista Corp. is affected by fluctuating interest rates related to a portion of its existing debt, and future borrowing requirements. The Finance Committee of the Board of Directors periodically reviews and discusses interest rate risk management processes, and it focuses on the steps management has undertaken to control it. The Risk Management Committee, composed of Company management, also reviews the interest risk management plan. Avista Corp. manages interest rate exposure by limiting the variable rate exposures to a percentage of total capitalization. Additionally, interest rate risk is managed by monitoring market conditions when timing the issuance of long-term debt and optional debt redemptions and through the use of fixed rate long-term debt with varying maturities. The Company also hedges a portion of its interest rate risk with financial derivative instruments, which may include interest rate swaps and U.S. Treasury lock agreements. These interest rate swaps and U.S. Treasury lock agreements are considered economic hedges against fluctuations in future cash flows associated with anticipated debt issuances.
	The following table summarizes the interest rate swaps that the Company has entered into as of March 31, 2014 and December 31, 2013 (dollars in thousands):
	Balance Sheet Date		Number of Contracts	Notional Amount				Mandatory Cash Settlement Date
	March 31, 2014		2	$	50,000			2014
			3	60,000				2015
			3	60,000				2016
			2	30,000				2017
			5	115,000				2018
	December 31, 2013		2	50,000				2014
			2	45,000				2015
			2	40,000				2016
			1	15,000				2017
			4	95,000				2018
	Upon settlement of interest rate swaps, the regulatory asset or liability (included as part of long-term debt) is amortized as a component of interest expense over the term of the associated debt.
	Derivative Instruments Summary
	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of March 31, 2014 (in thousands):
				Fair Value
	Derivative		Balance Sheet Location	Gross				Gross			Collateral			Net Asset				Gross Assets Not Offset			Gross Liabilities Not Offset			Net Asset (Liability)
				Asset				Liability			Netting			(Liability)
														in Balance
														Sheet
	Foreign currency contracts		Other current assets	$	47			$	(30	)	$	—		$	17			$	—		$	—		$	17
	Interest rate contracts		Other current assets	10,619				—			—			10,619				—			—			10,619
	Interest rate contracts		Other property and investments - net	10,641				(3,097		)	—			7,544				—			—			7,544
Interest rate contracts		Other non-current liabilities and deferred credits	—				(8,906		)	2,210			(6,696		)		—			—			(6,696		)
Commodity contracts (1)		Current utility energy commodity derivative assets	58,483				(41,846		)	(2,712		)	13,925				—			(158		)	13,767
Commodity contracts (1)		Non-current utility energy commodity derivative assets	31,510				(27,965		)	—			3,545				—			—			3,545
Commodity contracts (1)		Current utility energy commodity derivative liabilities	1,415				(4,775		)	—			(3,360		)		—			158			(3,202		)
Commodity contracts (1)		Other non-current liabilities and deferred credits	72				(15,271		)	—			(15,199		)		—			—			(15,199		)
Total derivative instruments recorded on the balance sheet			$	112,787			$	(101,890	)	$	(502	)	$	10,395			$	—		$	—		$	10,395
The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2013 (in thousands):
			Fair Value
Derivative		Balance Sheet Location	Gross				Gross			Collateral			Net Asset				Gross Assets Not Offset			Gross Liabilities Not Offset			Net Asset (Liability)
			Asset				Liability			Netting			(Liability)
													in Balance
													Sheet
Foreign currency contracts		Other current assets	$	7			$	(6	)	$	—		$	1			$	—		$	—		$	1
Interest rate contracts		Other current assets	13,968				—			—			13,968				—			—			13,968
Interest rate contracts		Other property and investments - net	19,575				—			—			19,575				—			—			19,575
Commodity contracts (1)		Current utility energy commodity derivative assets	7,416				(4,394		)	—			3,022				—			—			3,022
Commodity contracts (1)		Non-current utility energy commodity derivative assets	7,610				(6,756		)	—			854				—			—			854
Commodity contracts (1)		Current utility energy commodity derivative liabilities	23,455				(37,306		)	2,976			(10,875		)		—			—			(10,875		)
Commodity contracts (1)		Other non-current liabilities and deferred credits	17,101				(41,213		)	5,756			(18,356		)		—			—			(18,356		)
Total derivative instruments recorded on the balance sheet			$	89,132			$	(89,675	)	$	8,732		$	8,189			$	—		$	—		$	8,189
-1	Avista Corp. has a master netting agreement that governs the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allows for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performs cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. does not perform cross-affiliate netting because the Company believes that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 are not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there is no additional netting which requires disclosure for that period.
Exposure to Demands for Collateral
The Company's derivative contracts often require collateral (in the form of cash or letters of credit) or other credit enhancements, or reductions or terminations of a portion of the contract through cash settlement in the event of a downgrade in the Company's credit ratings or changes in market prices. In periods of price volatility, the level of exposure can change significantly. As a result, sudden and significant demands may be made against the Company's credit facilities and cash. The Company actively monitors the exposure to possible collateral calls and takes steps to mitigate capital requirements. As of March 31, 2014, the Company had deposited cash in the amount of $2.1 million and letters of credit of $2.5 million as collateral for certain energy derivative contracts. Conversely, the Company holds cash from other counterparties in the amount of $2.7 million as collateral for other energy derivative contracts. The Company also had deposited cash in the amount of $2.2 million as collateral for its interest rate swap derivative contracts. The Condensed Consolidated Balance Sheet at March 31, 2014 reflects the offsetting of $0.5 million of cash collateral against net derivative positions where a legal right of offset exists. As of December 31, 2013, the Company had deposited cash in the amount of $26.1 million and letters of credit of $20.3 million as collateral for certain energy derivative contracts. As of December 31, 2013, the Company did not hold any cash as collateral from counterparties for energy derivative contracts. The Consolidated Balance Sheet at December 31, 2013 reflects the offsetting of $8.7 million of cash collateral against net derivative positions where a legal right of offset exists.
Certain of the Company’s derivative instruments contain provisions that require the Company to maintain an "investment grade" credit rating from the major credit rating agencies. If the Company’s credit ratings were to fall below “investment grade,” it would be in violation of these provisions, and the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing collateralization on derivative instruments in net liability positions. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position as of March 31, 2014 was $3.8 million. If the credit-risk-related contingent features underlying these agreements were triggered on March 31, 2014, the Company could be required to post $2.9 million of additional collateral to its counterparties. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position as of December 31, 2013 was $13.3 million. If the credit-risk-related contingent features underlying these agreements had been triggered on December 31, 2013, the Company could have been required to post $12.6 million of additional collateral to its counterparties.
Credit Risk
Credit risk relates to the potential losses that the Company would incur as a result of non-performance by counterparties of their contractual obligations to deliver energy or make financial settlements. The Company often extends credit to counterparties and customers and is exposed to the risk that it may not be able to collect amounts owed to the Company. Credit risk includes potential counterparty default due to circumstances:
•	relating directly to it,
•	caused by market price changes, and
•	relating to other market participants that have a direct or indirect relationship with such counterparty.
Changes in market prices may dramatically alter the size of credit risk with counterparties, even when conservative credit limits are established. Should a counterparty fail to perform, the Company may be required to honor the underlying commitment or to replace existing contracts with contracts at then-current market prices.
The Company enters into bilateral transactions with various counterparties. The Company also trades energy and related derivative instruments through clearinghouse exchanges.
The Company seeks to mitigate bilateral credit risk by:
•	entering into bilateral contracts that specify credit terms and protections against default,
•	applying credit limits and duration criteria to existing and prospective counterparties,
•	actively monitoring current credit exposures,
•	asserting our collateral rights with counterparties,
•	carrying out transaction settlements timely and effectively, and
•	conducting transactions on exchanges with fully collateralized clearing arrangements that significantly reduce counterparty default risk.
The Company's credit policy includes an evaluation of the financial condition of counterparties. Credit risk management includes collateral requirements or other credit enhancements, such as letters of credit or parent company guarantees. The Company enters into various agreements that address credit risks including standardized agreements that allow for the netting or offsetting of positive and negative exposures.
The Company has concentrations of suppliers and customers in the electric and natural gas industries including:
•	electric and natural gas utilities,
•	electric generators and transmission providers,
•	natural gas producers and pipelines,
•	financial institutions including commodity clearing exchanges and related parties, and
•	energy marketing and trading companies.
In addition, the Company has concentrations of credit risk related to geographic location as it operates in the western United States and western Canada. These concentrations of counterparties and concentrations of geographic location may impact the Company’s overall exposure to credit risk because the counterparties may be similarly affected by changes in conditions.
The Company maintains credit support agreements with certain counterparties and margin calls are periodically made and/or received. Margin calls are triggered when exposures exceed contractual limits or when there are changes in a counterparty’s creditworthiness. Price movements in electricity and natural gas can generate exposure levels in excess of these contractual limits. Negotiating for collateral in the form of cash, letters of credit, or performance guarantees is common industry practice.

Pension_Plans_And_Other_Postre

Pension Plans And Other Postretirement Benefit Plans	3 Months Ended
	Mar. 31, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]	'
Pension Plans and Other Postretirement Benefit Plans	'
	PENSION PLANS AND OTHER POSTRETIREMENT BENEFIT PLANS
	The pension and other postretirement benefit plans described below only relate to Avista Utilities and do not cover any of the subsidiary employees. The Company's largest subsidiary, Ecova, has a 401(k) savings plan that is separate from those described below and this plan has historically not been significant to the Company.
	The Company has a defined benefit pension plan covering substantially all regular full-time employees at Avista Utilities. Individual benefits under this plan are based upon the employee’s years of service, date of hire and average compensation as specified in the plan. The Company’s funding policy is to contribute at least the minimum amounts that are required to be funded under the Employee Retirement Income Security Act, but not more than the maximum amounts that are currently deductible for income tax purposes. The Company contributed $11.0 million in cash to the pension plan for the three months ended March 31, 2014. The Company expects to contribute a total of $32.0 million in cash to the pension plan in 2014. The Company contributed $44.3 million in cash to the pension plan in 2013.
	In October 2013, the Company revised its defined benefit pension plan such that as of January 1, 2014 the plan is closed to all non-union employees hired or rehired by the Company on or after January 1, 2014. All actively employed non-union employees that were hired prior to January 1, 2014 and are currently covered under the defined benefit pension plan will continue accruing benefits as originally specified in the plan. A new and separate defined contribution 401(k) plan replaced the defined benefit pension plan for all non-union employees hired or rehired on or after January 1, 2014. Under the new defined contribution plan, the Company provides a non-elective contribution as a percentage of each employee's pay based on his or her age. This new defined contribution plan is in addition to the existing 401(k) plan in which the Company matches a portion of the pay deferred by each participant. In addition to the above changes, the Company has also revised its lump sum calculation from its previous lump sum calculation for non-union participants who retire under the defined benefit pension plan to provide non-union retirees on or after January 1, 2014 with a lump sum amount equivalent to the present value of the annuity based upon applicable discount rates. In April 2014, the local union in Oregon for the International Brotherhood of Electrical Workers accepted the above plan changes in the latest collective bargaining agreement, and the plan changes are effective for Oregon union workers hired or rehired on or after April 1, 2014.
	The Company also has a Supplemental Executive Retirement Plan (SERP) that provides additional pension benefits to executive officers of the Company. The SERP is intended to provide benefits to executive officers whose benefits under the pension plan are reduced due to the application of Section 415 of the Internal Revenue Code of 1986 and the deferral of salary under deferred compensation plans. The liability and expense for this plan are included as pension benefits in the tables included in this Note.
	The Company provides certain health care and life insurance benefits for substantially all of its retired employees. The Company accrues the estimated cost of postretirement benefit obligations during the years that employees provide services. In October 2013, the Company revised the health care benefit plan such that beginning on January 1, 2020, the method for calculating health insurance premiums for non-union retirees under age 65 and active Company employees was revised. The revisions resulted in separate health insurance premium calculations for each group. In addition, for non-union employees hired or rehired on or after January 1, 2014, upon retirement the Company will provide access to its retiree medical plan, but will no longer provides a contribution towards his or her medical premiums and the employee will pay the full cost of premiums upon retirement. In April 2014, the local union in Oregon for the International Brotherhood of Electrical Workers accepted the above plan changes in the latest collective bargaining agreement, and the plan changes are effective for Oregon union workers hired or rehired on or after April 1, 2014.
	The Company has a Health Reimbursement Arrangement to provide employees with tax-advantaged funds to pay for allowable medical expenses upon retirement. The amount earned by the employee is fixed on the retirement date based on the employee’s years of service and the ending salary. The liability and expense of this plan are included as other postretirement benefits.
	The Company provides death benefits to beneficiaries of executive officers who die during their term of office or after retirement. Under the plan, an executive officer’s designated beneficiary will receive a payment equal to twice the executive officer’s annual base salary at the time of death (or if death occurs after retirement, a payment equal to twice the executive officer’s total annual pension benefit). The liability and expense for this plan are included as other postretirement benefits.
	The Company uses a December 31 measurement date for its pension and other postretirement benefit plans. The following table sets forth the components of net periodic benefit costs for the three months ended March 31 (dollars in thousands):
		Pension Benefits						Other Post-retirement Benefits
		2014			2013			2014			2013
	Three months ended March 31:
	Service cost	$	5,018		$	4,743		$	974		$	1,032
	Interest cost	6,706			5,978			1,353			1,390
	Expected return on plan assets	(8,110		)	(6,900		)	(472		)	(400		)
	Amortization of prior service cost	6			75			(43		)	(37		)
	Net loss recognition	1,157			3,547			826			1,521
	Net periodic benefit cost	$	4,777		$	7,443		$	2,638		$	3,506

Committed_Lines_of_Credit

Committed Lines of Credit	3 Months Ended
	Mar. 31, 2014
Short-term Debt [Abstract]	'
Committed Lines of Credit	'
	COMMITTED LINES OF CREDIT
	Avista Corp.
	Avista Corp. has a committed line of credit with various financial institutions in the total amount of $400 million. In April 2014, the Company amended this committed line of credit agreement to extend the expiration date to April 2019. The amendment also provides the Company the option to request an extension for an additional one or two years beyond April 2019, provided there is no event of default prior to the requested extension and the requested extension does not cause the remaining term until the expiration date to exceed five years. The amendment did not change the amount of the committed line of credit.
	The committed line of credit is secured by non-transferable First Mortgage Bonds of the Company issued to the agent bank that would only become due and payable in the event, and then only to the extent, that the Company defaults on its obligations under the committed line of credit.
	The committed line of credit agreement contains customary covenants and default provisions. The credit agreement has a covenant which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” of Avista Corp. to be greater than 65 percent at any time. As of March 31, 2014, the Company was in compliance with this covenant.
	Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed lines of credit were as follows as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,			December 31,
		2014			2013
	Borrowings outstanding at end of period	$	111,000		$	171,000
	Letters of credit outstanding at end of period	$	9,614		$	27,434
	Average interest rate on borrowings at end of period	0.93		%	1.02		%
	As of March 31, 2014 the borrowings outstanding under Avista Corp.'s committed line of credit were classified as short-term borrowings on the Condensed Consolidated Balance Sheet.
	Ecova
	Ecova has a $125.0 million committed line of credit agreement with various financial institutions that has an expiration date of July 2017. The credit agreement is secured by all of Ecova's assets excluding investments and funds held for clients.
	The committed line of credit agreement contains customary covenants and default provisions, including a covenant which requires that Ecova's “Consolidated Total Funded Debt to EBITDA Ratio” (as defined in the credit agreement) must be 2.50 to 1.00 or less, with provisions in the credit agreement allowing for a temporary increase of this ratio if a qualified acquisition is consummated by Ecova. In addition, Ecova's “Consolidated Fixed Charge Coverage Ratio” (as defined in the credit agreement) must be greater than 1.50 to 1.00 as of the last day of any fiscal quarter. As of March 31, 2014, Ecova was in compliance with these covenants.
	Balances outstanding and interest rates of borrowings under Ecova’s credit agreements were as follows as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,			December 31,
		2014			2013
	Borrowings outstanding at end of period	$	42,000		$	46,000
	Average interest rate on borrowings at end of period	2.16		%	2.17		%
	As of March 31, 2014 the borrowings outstanding under Ecova's committed line of credit were classified as long-term borrowings under committed line of credit on the Condensed Consolidated Balance Sheet.

LongTerm_Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2014
Long-term Debt, Unclassified [Abstract]	'
Long-Term Debt	'
	LONG-TERM DEBT
	The following details long-term debt outstanding as of March 31, 2014 and December 31, 2013 (dollars in thousands):
	Maturity			Interest	March 31,			December 31,
	Year		Description	Rate	2014			2013
	2016		First Mortgage Bonds	0.84%	$	90,000		$	90,000
	2018		First Mortgage Bonds	5.95%	250,000			250,000
	2018		Secured Medium-Term Notes	7.39%-7.45%	22,500			22,500
	2019		First Mortgage Bonds	5.45%	90,000			90,000
	2020		First Mortgage Bonds	3.89%	52,000			52,000
	2022		First Mortgage Bonds	5.13%	250,000			250,000
	2023		Secured Medium-Term Notes	7.18%-7.54%	13,500			13,500
	2028		Secured Medium-Term Notes	6.37%	25,000			25,000
	2032		Secured Pollution Control Bonds (1)	-1	66,700			66,700
	2034		Secured Pollution Control Bonds (1)	-1	17,000			17,000
	2035		First Mortgage Bonds	6.25%	150,000			150,000
	2037		First Mortgage Bonds	5.70%	150,000			150,000
	2040		First Mortgage Bonds	5.55%	35,000			35,000
	2041		First Mortgage Bonds	4.45%	85,000			85,000
	2047		First Mortgage Bonds	4.23%	80,000			80,000
			Total secured long-term debt		1,376,700			1,376,700
			Other long-term debt and capital leases		4,561			4,630
			Settled interest rate swaps (2)		(23,413		)	(23,560		)
			Unamortized debt discount		(1,246		)	(1,287		)
			Total		1,356,602			1,356,483
			Secured Pollution Control Bonds held by Avista Corporation (1)		(83,700		)	(83,700		)
			Current portion of long-term debt		(372		)	(358		)
			Total long-term debt		$	1,272,530		$	1,272,425
	-1	In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.
	-2	Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.
	Nonrecourse Long-Term Debt
	Nonrecourse long-term debt (including current portion) represents the long-term debt of Spokane Energy. To provide funding to acquire a long-term fixed rate electric capacity contract from Avista Corp., Spokane Energy borrowed $145.0 million from a funding trust in December 1998. The long-term debt has scheduled monthly installments and interest at a fixed rate of 8.45 percent with the final payment due in January 2015. Spokane Energy bears full recourse risk for the debt, which is secured by the fixed rate electric capacity contract and $1.6 million of funds held in a trust account. As of March 31, 2014, the entire remaining portion of the nonrecourse debt has been included in current liabilities due to its maturity in January 2015.

Fair_Value

Fair Value	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value	'
	FAIR VALUE
	The carrying values of cash and cash equivalents, accounts and notes receivable, accounts payable and short-term borrowings are reasonable estimates of their fair values. Long-term debt (including current portion, but excluding capital leases), nonrecourse long-term debt and long-term debt to affiliated trusts are reported at carrying value on the Condensed Consolidated Balance Sheets.
	The fair value hierarchy prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement).
	The three levels of the fair value hierarchy are defined as follows:
	Level 1 – Quoted prices are available in active markets for identical assets or liabilities. Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis.
	Level 2 – Pricing inputs are other than quoted prices in active markets included in Level 1, which are either directly or indirectly observable as of the reporting date. Level 2 includes those financial instruments that are valued using models or other valuation methodologies. These models are primarily industry-standard models that consider various assumptions, including quoted forward prices for commodities, time value, volatility factors, and current market and contractual prices for the underlying instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace.
	Level 3 – Pricing inputs include significant inputs that are generally unobservable from objective sources. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value.
	Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels. The determination of the fair values incorporates various factors that not only include the credit standing of the counterparties involved and the impact of credit enhancements (such as cash deposits and letters of credit), but also the impact of Avista Corp.’s nonperformance risk on its liabilities.
	The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Condensed Consolidated Balance Sheets as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31, 2014								December 31, 2013
		Carrying				Estimated				Carrying			Estimated
		Value				Fair Value				Value			Fair Value
	Long-term debt (Level 2)	$	951,000			$	1,080,124			$	951,000		$	1,054,512
	Long-term debt (Level 3)	342,000				345,980				342,000			329,581
	Nonrecourse long-term debt (Level 3)	13,872				14,323				17,838			18,636
	Long-term debt to affiliated trusts (Level 3)	51,547				37,052				51,547			37,114
	These estimates of fair value of long-term debt and long-term debt to affiliated trusts were primarily based on available market information. Due to the unique nature of the long-term fixed rate electric capacity contract securing the long-term debt of Spokane Energy (nonrecourse long-term debt), the estimated fair value of nonrecourse long-term debt was determined based on a discounted cash flow model using available market information.
	The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Condensed Consolidated Balance Sheets as of March 31, 2014 and December 31, 2013 at fair value on a recurring basis (dollars in thousands):
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	31-Mar-14
	Assets:
	Energy commodity derivatives	$	—			$	91,090			$	—		$	(73,620	)	$	17,470
	Level 3 energy commodity derivatives:
	Power exchange agreement	—				—				390			(390		)	—
	Foreign currency derivatives	—				47				—			(30		)	17
	Interest rate swaps	—				21,260				—			(3,097		)	18,163
	Investments and funds held for clients:
	Money market funds	23,034				—				—			—			23,034
	Securities available for sale:
	U.S. government agency	—				54,327				—			—			54,327
	Municipal	—				3,109				—			—			3,109
	Corporate fixed income – industrial	—				763				—			—			763
	Certificate of deposits	—				1,000				—			—			1,000
	Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
	Deferred compensation assets:
	Fixed income securities (2)	1,906				—				—			—			1,906
	Equity securities (2)	6,475				—				—			—			6,475
	Total	$	33,015			$	171,596			$	390		$	(77,137	)	$	127,864
	Liabilities:
	Energy commodity derivatives	$	—			$	72,997			$	—		$	(70,908	)	$	2,089
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				2,418			—			2,418
	Power exchange agreement	—				—				14,014			(390		)	13,624
	Power option agreement	—				—				428			—			428
	Foreign currency derivatives	—				30				—			(30		)	—
	Interest rate swaps	—				12,003				—			(5,307		)	6,696
	Total	$	—			$	85,030			$	16,860		$	(76,635	)	$	25,255
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	31-Dec-13
	Assets:
	Energy commodity derivatives	$	—			$	55,243			$	—		$	(51,367	)	$	3,876
	Level 3 energy commodity derivatives:
	Power exchange agreement	—				—				339			(339		)	—
	Foreign currency derivatives	—				7				—			(6		)	1
	Interest rate swaps	—				33,543				—			—			33,543
	Investments and funds held for clients:
	Money market funds	11,180				—				—			—			11,180
Securities available for sale:
U.S. government agency	—				61,078				—			—			61,078
Municipal	—				3,518				—			—			3,518
Corporate fixed income – financial	—				3,000				—			—			3,000
Corporate fixed income – industrial	—				765				—			—			765
Certificate of deposits	—				1,000				—			—			1,000
Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
Deferred compensation assets:
Fixed income securities (2)	1,960				—				—			—			1,960
Equity securities (2)	6,470				—				—			—			6,470
Total	$	21,210			$	158,154			$	339		$	(51,712	)	$	127,991
Liabilities:
Energy commodity derivatives	$	—			$	72,895			$	—		$	(60,099	)	$	12,796
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—				—				1,219			—			1,219
Power exchange agreement	—				—				14,780			(339		)	14,441
Power option agreement	—				—				775			—			775
Foreign currency derivatives	—				6				—			(6		)	—
Total	$	—			$	72,901			$	16,774		$	(60,444	)	$	29,231
-1	The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties.
-2	These assets are trading securities and are included in other property and investments-net on the Condensed Consolidated Balance Sheets.
Avista Corp. enters into forward contracts to purchase or sell a specified amount of energy at a specified time, or during a specified period, in the future. These contracts are entered into as part of Avista Corp.’s management of loads and resources and certain contracts are considered derivative instruments. The difference between the amount of derivative assets and liabilities disclosed in respective levels and the amount of derivative assets and liabilities disclosed on the Condensed Consolidated Balance Sheets is due to netting arrangements with certain counterparties. The Company uses quoted market prices and forward price curves to estimate the fair value of utility derivative commodity instruments included in Level 2. In particular, electric derivative valuations are performed using broker quotes, adjusted for periods in between quotable periods. Natural gas derivative valuations are estimated using New York Mercantile Exchange (NYMEX) pricing for similar instruments, adjusted for basin differences, using broker quotes. Where observable inputs are available for substantially the full term of the contract, the derivative asset or liability is included in Level 2.
For securities available for sale (held at Ecova) Ecova uses a nationally recognized third party to obtain fair value and reviews these prices for accuracy using a variety of market tools and analyses. Ecova's pricing vendor uses a generic model which uses standard inputs, including (listed in order of priority for use) benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, market bids/offers and other reference data. The pricing vendor also monitors market indicators, as well as industry and economic events. All securities available for sale were deemed Level 2.
Deferred compensation assets and liabilities represent funds held by the Company in a Rabbi Trust for an executive deferral plan. These funds consist of actively traded equity and bond funds with quoted prices in active markets. The balance disclosed in the table above excludes cash and cash equivalents of $0.9 million as of March 31, 2014 and $0.7 million as of December 31, 2013.
Level 3 Fair Value
For the power exchange agreement, the Company compares the Level 2 brokered quotes and forward price curves described above to an internally developed forward price which is based on the average operating and maintenance (O&M) charges from four surrogate nuclear power plants around the country for the current year. Because the nuclear power plant O&M charges are only known for one year, all forward years are estimated assuming an annual escalation. In addition to the forward price being estimated using unobservable inputs, the Company also estimates the volumes of the transactions that will take place in the future based on historical average transaction volumes per delivery year (November to April). Significant increases or decreases in any of these inputs in isolation would result in a significantly higher or lower fair value measurement. Generally, a change in the current year O&M charges for the surrogate plants is accompanied by a directionally similar change in O&M charges in future years. There is generally not a correlation between external market prices and the O&M charges used to develop the internal forward price.
For the power commodity option agreement, the Company uses the Black-Scholes-Merton valuation model to estimate the fair value, and this model includes significant inputs not observable or corroborated in the market. These inputs include 1) the strike price (which is an internally derived price based on a combination of generation plant heat rate factors, natural gas market pricing, delivery and other O&M charges, 2) estimated delivery volumes for years beyond 2013, and 3) volatility rates for periods beyond April 2017. Significant increases or decreases in any of these inputs in isolation would result in a significantly higher or lower fair value measurement. Generally, changes in overall commodity market prices and volatility rates are accompanied by directionally similar changes in the strike price and volatility assumptions used in the calculation.
For the natural gas commodity exchange agreement, the Company uses the same Level 2 brokered quotes described above; however, the Company also estimates the purchase and sales volumes (within contractual limits) as well as the timing of those transactions. Changing the timing of volume estimates changes the timing of purchases and sales, impacting which brokered quote is used. Because the brokered quotes can vary significantly from period to period, the unobservable estimates of the timing and volume of transactions can have a significant impact on the calculated fair value. The Company currently estimates volumes and timing of transactions based on a most likely scenario using historical data. Historically, the timing and volume of transactions have not been highly correlated with market prices and market volatility.
The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of March 31, 2014 (dollars in thousands):
		Fair Value (Net) at
		March 31, 2014				Valuation Technique		Unobservable		Range
								Input
Power exchange agreement		$	(13,624	)		Surrogate facility		O&M charges		$30.18-$53.90/MWh (1)
						pricing		Escalation factor		3% - 2014 to 2019
								Transaction volumes		396,984 - 397,116 MWhs
Power option agreement		(428		)		Black-Scholes-		Strike price		$56.53/MWh - 2016
						Merton				$69.98/MWh - 2015
								Delivery volumes		128,278 - 286,307 MWhs
								Volatility rates		0.20 (2)
Natural gas exchange		(2,418		)		Internally derived		Forward purchase		$3.66 - $4.45/mmBTU
agreement						weighted average		prices
						cost of gas		Forward sales prices		$4.54 - $5.23/mmBTU
								Purchase volumes		280,000 - 310,000 mmBTUs
								Sales volumes		279,990 - 310,000 mmBTUs
(1) The average O&M charges for the delivery year beginning in November 2013 were $40.93 per MWh. For ratemaking purposes the average O&M calculations vary slightly between regulatory jurisdictions. The average O&M charges for the delivery year beginning in 2013 were $42.44 for Washington and $40.93 for Idaho.
(2) The estimated volatility rate of 0.20 is compared to actual quoted volatility rates of 0.31 for 2014 to 0.18 in April 2017.
Avista Corp.'s risk management team and accounting team are responsible for developing the valuation methods described above and both groups report to the Chief Financial Officer. The valuation methods, significant inputs and resulting fair values described above are reviewed on at least a quarterly basis by the risk management team and the accounting team to ensure they provide a reasonable estimate of fair value each reporting period.
The following table presents activity for energy commodity derivative assets (liabilities) measured at fair value using significant unobservable inputs (Level 3) for the three months ended March 31 (dollars in thousands):
	Natural Gas Exchange Agreement				Power Exchange Agreement				Power Option Agreement			Total
Three months ended March 31, 2014:
Balance as of January 1, 2014	$	(1,219	)		$	(14,441	)		$	(775	)	$	(16,435	)
Total gains or losses (realized/unrealized):
Included in net income	—				—				—			—
Included in other comprehensive income	—				—				—			—
Included in regulatory assets/liabilities (1)	1,849				2,026				347			4,222
Purchases	—				—				—			—
Issuance	—				—				—			—
Settlements	(3,048		)		(1,209		)		—			(4,257		)
Transfers to/from other categories	—				—				—			—
Ending balance as of March 31, 2014	$	(2,418	)		$	(13,624	)		$	(428	)	$	(16,470	)
Three months ended March 31, 2013:
Balance as of January 1, 2013	$	(2,379	)		$	(18,692	)		$	(1,480	)	$	(22,551	)
Total gains or losses (realized/unrealized):
Included in net income	—				—				—			—
Included in other comprehensive income	—				—				—			—
Included in regulatory assets/liabilities (1)	750				24				280			1,054
Purchases	—				—				—			—
Issuance	—				—				—			—
Settlements	(362		)		2,205				—			1,843
Transfers from other categories	—				—				—			—
Ending balance as of March 31, 2013	$	(1,991	)		$	(16,463	)		$	(1,200	)	$	(19,654	)
-1	The UTC and the IPUC issued accounting orders authorizing Avista Corp. to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Corp. to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates cases.

Earnings_Per_Common_Share_Attr

Earnings Per Common Share Attributable To Avista Corporation	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Common Share Attributable To Avista Corporation Shareholders	'
	EARNINGS PER COMMON SHARE ATTRIBUTABLE TO AVISTA CORPORATION SHAREHOLDERS
	The following table presents the computation of basic and diluted earnings per common share attributable to Avista Corporation shareholders for the three months ended March 31 (in thousands, except per share amounts):
		2014			2013
	Numerator:
	Net income attributable to Avista Corporation shareholders	$	48,499		$	42,341
	Subsidiary earnings adjustment for dilutive securities	(53		)	(43		)
	Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$	48,446		$	42,298
	Denominator:
	Weighted-average number of common shares outstanding-basic	60,122			59,866
	Effect of dilutive securities:
	Performance and restricted stock awards	46			32
	Weighted-average number of common shares outstanding-diluted	60,168			59,898
	Earnings per common share attributable to Avista Corporation shareholders:
	Basic	$	0.81		$	0.71
	Diluted	$	0.81		$	0.71
	There were no shares excluded from the calculation because they were antidilutive.

Commitments_And_Contingencies

Commitments And Contingencies	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments And Contingencies	'
	COMMITMENTS AND CONTINGENCIES
	In the course of its business, the Company becomes involved in various claims, controversies, disputes and other contingent matters, including the items described in this Note. Some of these claims, controversies, disputes and other contingent matters involve litigation or other contested proceedings. For all such matters, the Company intends to vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any particular matter because litigation and other contested proceedings are inherently subject to numerous uncertainties. For matters that affect Avista Utilities’ operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process.
	Federal Energy Regulatory Commission Inquiry
	In April 2004, the Federal Energy Regulatory Commission (FERC) approved the contested Agreement in Resolution of Section 206 Proceeding (Agreement in Resolution) between Avista Corp. doing business as Avista Utilities, Avista Energy and the FERC's Trial Staff which stated that there was: (1) no evidence that any executives or employees of Avista Utilities or Avista Energy knowingly engaged in or facilitated any improper trading strategy during 2000 and 2001; (2) no evidence that Avista Utilities or Avista Energy engaged in any efforts to manipulate the western energy markets during 2000 and 2001; and (3) no finding that Avista Utilities or Avista Energy withheld relevant information from the FERC's inquiry into the western energy markets for 2000 and 2001 (Trading Investigation). Appeals of the FERC’s decisions approving the Agreement in Resolution are pending before the United States Court of Appeals for the Ninth Circuit (Ninth Circuit). In May 2004, the FERC provided notice that Avista Energy was no longer subject to an investigation reviewing certain bids above $250 per MW in the short-term energy markets operated by the California Independent System Operator (CalISO) and the California Power Exchange (CalPX) from May 1, 2000 to October 2, 2000 (Bidding Investigation). Appeal of this FERC decision is also pending before the Ninth Circuit.
	As discussed in "California Refund Proceeding" below, on March 7, 2014, Avista Utilities and Avista Energy filed at FERC a settlement with Pacific Gas & Electric (PG&E), Southern California Edison, San Diego Gas & Electric, the California Attorney General (AG), the California Department of Water Resources (CERS), and the California Public Utilities Commission (together, the “California Parties”) that resolves, inter alia, both the Trading Investigation and the Bidding Investigation. The settlement is subject to FERC’s approval. The Company does not expect that this matter will have a material adverse effect on its financial condition, results of operations or cash flows.
	California Refund Proceeding
	In July 2001, the FERC ordered an evidentiary hearing to determine the amount of refunds due to California energy buyers for purchases made in the spot markets operated by the CalISO and the CalPX during the period from October 2, 2000 to June 20, 2001 (Refund Period). Proposed refunds are based on the calculation of mitigated market clearing prices for each hour. The FERC ruled that if the refunds required by the formula would cause a seller to recover less than its actual costs for the Refund Period, sellers may document these costs and limit their refund liability commensurately. In 2011, the FERC approved Avista Energy’s cost filing, a decision that is now before the Ninth Circuit.
	In August 2006, the Ninth Circuit remanded to the FERC its decision not to consider an FPA section 309 remedy for tariff violations prior to October 2, 2000. In May 2011, the FERC clarified the issues set for hearing for the period May 1, 2000 - October 1, 2000 (Summer Period): (1) which market practices and behaviors constitute a violation of the then-current CalISO, CalPX, and individual seller's tariffs and FERC orders; (2) whether any of the sellers named as respondents in this proceeding engaged in those tariff violations; and (3) whether any such tariff violations affected the market clearing price. The FERC also gave the claimants an opportunity to show that exchange transactions with the CalISO during the Refund Period were not just and reasonable. During a FERC hearing in 2012, the Presiding Administrative Law Judge (ALJ) issued a partial initial decision granting Avista Utilities' motion for summary disposition, based on the stipulation by the parties that there are no allegations of tariff violations made against Avista Utilities in this proceeding and therefore no tariff violations by Avista Utilities that affected the market clearing price in any hour during the Summer Period. On November 2, 2012, the FERC issued an order affirming the partial initial decision and dismissing Avista Utilities from the proceeding, thereby terminating all claims against Avista Utilities for the Summer Period. In the same order, the FERC also held that a market-wide remedy would not be appropriate with regard to any respondent during the Summer Period. On February 15, 2013, the ALJ issued an initial decision ruling that the claimants met their burden in the case against Avista Energy by relying on “screens” that identified transactions that potentially could have signified tariff violations. The initial decision did not discuss evidence offered by Avista Energy, on an hour-by-hour basis, rebutting the alleged violations. With respect to Avista Energy's one exchange transaction with the CalISO during the Refund Period, the judge made no findings with respect to the justness and reasonableness of that transaction, but nonetheless determined that Avista Energy owed approximately $0.2 million in refunds with regard to the transaction.
	On March 7, 2014, Avista Utilities, Avista Energy and the California Parties filed a settlement at the FERC that would resolve these matters. The 2001 bankruptcy of PG&E resulted in a default on its payment obligations to the CalPX, and as a result, Avista Energy has not been paid for all of its sales during the Refund Period. Those funds have been held in escrow accounts pending resolution of this proceeding. The settlement, which is pending the FERC's approval, would return $15 million of Avista Energy’s receivable to Avista Energy, with the balance of the Avista Energy receivable flowing to the purchasers associated with the hourly transactions at issue. There is no admission of wrongdoing on the part of the settling parties, and thus it is further agreed that no part of the refund payment by Avista Energy constitutes a fine or a penalty. The settlement resolves all claims for alleged overcharges during the Summer and Refund Periods in the California Refund Proceeding, and in the Pacific Northwest Refund Proceeding (for sales made to CERS), as discussed below. The settlement also includes settlement of the Trading Investigation, the Bidding Investigation and the California Attorney General Complaint (the "Lockyer Complaint").
	The Company does not expect that this matter will have a material adverse effect on its financial condition, results of operations or cash flows.
	Pacific Northwest Refund Proceeding
	In July 2001, the FERC initiated a preliminary evidentiary hearing to develop a factual record as to whether prices for spot market sales of wholesale energy in the Pacific Northwest between December 25, 2000 and June 20, 2001 were just and reasonable. In June 2003, the FERC terminated the Pacific Northwest refund proceedings, after finding that the equities do not justify the imposition of refunds. In August 2007, the Ninth Circuit found that the FERC, in denying the request for refunds, had failed to take into account new evidence of market manipulation in the California energy market and its potential ties to the Pacific Northwest energy market and that such failure was arbitrary and capricious and, accordingly, remanded the case to the FERC, stating that the FERC's findings must be reevaluated in light of the evidence. The Ninth Circuit expressly declined to direct the FERC to grant refunds. On October 3, 2011, the FERC issued an Order on Remand, finding that, in light of the Ninth Circuit's remand order, additional procedures are needed to address possible unlawful activity that may have influenced prices in the Pacific Northwest spot market during the period from December 25, 2000 through June 20, 2001. The Order on Remand established an evidentiary, trial-type hearing before an ALJ, and reopened the record to permit parties to present evidence of unlawful market activity. The Order on Remand stated that parties seeking refunds must submit evidence demonstrating that specific unlawful market activity occurred, and must demonstrate that such activity directly affected negotiations with respect to the specific contract rate about which they complain. Simply alleging a general link between the dysfunctional spot market in California and the Pacific Northwest spot market will not be sufficient to establish a causal connection between a particular seller's alleged unlawful activities and the specific contract negotiations at issue.
	On July 11, 2012, Avista Energy and Avista Utilities filed settlements of all issues in this docket with regard to the claims made by the City of Tacoma, which the FERC approved. The two remaining direct claimants against Avista Utilities and Avista Energy in this proceeding are the City of Seattle, Washington (Seattle), and the California AG (on behalf of CERS).
	On April 5, 2013, the FERC issued an Order on Rehearing expanding the temporal scope of the proceeding to permit parties to submit evidence on transactions during the period from January 1, 2000 through and including June 20, 2001.
	On April 11, 2013, certain of the California Parties filed a petition for review of the October 3, 2011 Order on Remand, and the April 5, 2013 Order on Rehearing, in the Ninth Circuit. Seattle filed a petition for review of the same orders on April 26, 2013.
	The hearing before an ALJ began on August 27, 2013.
	As discussed in "California Refund Proceeding" above, on March 7, 2014, the Company and the California Parties filed at the FERC a settlement that encompasses the CERS claims in this proceeding, obviating the need for additional litigation.
	With regard to the Seattle claims, on March 28, 2014, the Presiding ALJ issued her initial decision finding that: (1) Seattle failed to demonstrate that either Avista Utilities or Avista Energy engaged in unlawful market activity and also failed to identify any specific contracts at issue; (2) Seattle failed to demonstrate that contracts with either Avista Utilities or Avista Energy imposed an excessive burden on consumers or seriously harmed the public interest; and that (3) Seattle failed to demonstrate that either Avista Utilities or Avista Energy engaged in any specific violations of substantive provisions of the Federal Power Act or any filed tariffs or rate schedules. Accordingly, the ALJ denied all of Seattle’s claims under both section 206 and section 309 of the Federal Power Act. Briefs on exceptions are due May 12, 2014 and briefs opposing exceptions are due June 16, 2014. The Company does not expect that this matter will have a material adverse effect on its financial condition, results of operations or cash flows.
	California Attorney General Complaint (the “Lockyer Complaint”)
	In May 2002, the FERC conditionally dismissed a complaint filed in March 2002 by the California AG that alleged violations of the FPA by the FERC and all sellers (including Avista Corp. and its subsidiaries) of electric power and energy into California. The complaint alleged that the FERC's adoption and implementation of market-based rate authority was flawed and, as a result, individual sellers should refund the difference between the rate charged and a just and reasonable rate. In May 2002, the FERC issued an order dismissing the complaint. In September 2004, the Ninth Circuit upheld the FERC's market-based rate authority, but held that the FERC erred in ruling that it lacked authority to order refunds for violations of its reporting requirement. The Court remanded the case for further proceedings, which ultimately resulted in summary disposition at the FERC in favor of Avista Utilities and Avista Energy. The proceeding is now before the Ninth Circuit.
	As discussed in "California Refund Proceeding" above, on March 7, 2014, Avista Utilities, Avista Energy and the California Parties filed a settlement at the FERC that resolves these matters. The settlement is subject to approval by the FERC. The Company does not expect that this matter will have a material adverse effect on its financial condition, results of operations or cash flows.
	Sierra Club and Montana Environmental Information Center Litigation
	On March 6, 2013, the Sierra Club and Montana Environmental Information Center (MEIC) (collectively "Plaintiffs"), filed a Complaint in the United States District Court for the District of Montana, Billings Division, against the Owners of the Colstrip Generating Project ("Colstrip"). Avista Corp. owns a 15 percent interest in Units 3 & 4 of Colstrip. The other Colstrip co-Owners are PPL Montana, Puget Sound Energy, Portland General Electric Company, NorthWestern Energy and PacifiCorp. The Complaint alleges certain violations of the Clean Air Act, including the New Source Review, Title V and opacity requirements. The Plaintiffs request that the Court grant injunctive and declaratory relief, impose civil penalties, require a beneficial environmental project in the areas affected by the alleged air pollution and require payment of Plaintiffs' costs of litigation and attorney fees.
	On May 3, 2013, the Colstrip Owners filed a Partial Motion to Dismiss, seeking dismissal of 36 of the 39 claims. The Plaintiffs filed their opposition on May 31, 2013, and the Owners filed their reply on June 21, 2013. On July 17, 2013, the Court held a preliminary pretrial conference, and on July 18, 2013, the Court issued an Order establishing a procedural schedule and deadlines.
	On September 12, 2013, the Plaintiffs filed Plaintiffs’ First Motion for Partial Summary Judgment on the Applicable Method for Calculating Emission Increases from Modifications Made to the Colstrip Power Plant. The Colstrip Owners filed their opposition on November 15, 2013. On November 19, 2013, the Court issued an Order granting the Montana Department of Environmental Quality permission to file an amicus brief concerning Plaintiffs' Motion.
	On September 27, 2013, the Plaintiffs filed an Amended Complaint. The Amended Complaint withdrew from the original Complaint fifteen claims related to seven pre-January 1, 2001 Colstrip maintenance projects, upgrade projects and work projects and claims alleging violations of Title V and opacity requirements. The Amended Complaint alleges certain violations of the Clean Air Act and the New Source Review and adds claims with respect to post-January 1, 2001 Colstrip projects. The Plaintiffs request that the Court grant injunctive and declaratory relief, order remediation of alleged environmental damage, impose civil penalties, require a beneficial environmental project in the areas affected by the alleged air pollution and require payment of Plaintiffs’ costs of litigation and attorney fees.
	On October 11, 2013, the Colstrip Owners filed a Motion to Dismiss, seeking dismissal of all of Plaintiffs' claims contained in the Amended Complaint.
	On January 23, 2014, the Court issued an Order amending the procedural schedule and deadlines.
	On April 18, 2014, the Court issued an Order setting May 6, 2014 as the date the Court will hear oral argument on the Colstrip Owners' Motion to Dismiss and Plaintiffs' Motion for Partial Summary Judgment.
	Due to the preliminary nature of the lawsuit, Avista Corporation cannot, at this time, predict the outcome of the matter.
	Spokane River Licensing
	The Company owns and operates six hydroelectric plants on the Spokane River. Five of these (Long Lake, Nine Mile, Upper Falls, Monroe Street, and Post Falls) are regulated under one 50-year FERC license issued in June 2009 and are referred to as the Spokane River Project. The sixth, Little Falls, is operated under separate Congressional authority and is not licensed by the FERC. The license incorporated the 4(e) conditions that were included in the December 2008 Settlement Agreement with the United States Department of Interior and the Coeur d’Alene Tribe, as well as the mandatory conditions that were agreed to in the Idaho 401 Water Quality Certifications and in the amended Washington 401 Water Quality Certification.
	As part of the Settlement Agreement with the Washington Department of Ecology (Ecology), the Company has participated in the Total Maximum Daily Load (TMDL) process for the Spokane River and Lake Spokane, the reservoir created by Long Lake Dam. On May 20, 2010, the EPA approved the TMDL and on May 27, 2010, Ecology filed an amended 401 Water Quality Certification with the FERC for inclusion into the license. The amended 401 Water Quality Certification includes the Company's level of responsibility, as defined in the TMDL, for low dissolved oxygen levels in Lake Spokane. The Company submitted a draft Water Quality Attainment Plan for Dissolved Oxygen to Ecology in May 2012 and this was approved by Ecology in September 2012. This plan was subsequently approved by the FERC. The Company began implementing this plan in 2013, and management believes costs will not be material. On July 16, 2010, the City of Post Falls and the Hayden Area Regional Sewer Board filed an appeal with the United States District Court for the District of Idaho with respect to the EPA's approval of the TMDL. The Company, the City of Coeur d'Alene, Kaiser Aluminum and the Spokane River Keeper subsequently moved to intervene in the appeal. In September 2011, the EPA issued a stay to the litigation that will be in effect until either the permits are issued and all appeals and challenges are complete or the court lifts the stay. The stay is still in effect.
	During 2013, through a collaborative process with key stakeholders, a decision was reached to not move forward with a specific capital project to add oxygen to Lake Spokane. At the time of such decision, the Company had expended $1.3 million on the discontinued project. On September 26, 2013 and October 23, 2013, the UTC and IPUC, respectively, issued Orders approving the Company's petition for an accounting order authorizing deferral of costs related to the discontinued project. The Washington portion of the project costs were $0.9 million and the Idaho portion were $0.5 million and these costs have been recorded as regulatory assets. The Company intends to seek recovery of these costs through the ratemaking process.
	The UTC and IPUC approved the recovery of licensing costs through the general rate case settlements in 2009. The Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to implementing the license for the Spokane River Project.
	Cabinet Gorge Total Dissolved Gas Abatement Plan
	Dissolved atmospheric gas levels in the Clark Fork River exceed state of Idaho and federal water quality standards downstream of the Cabinet Gorge Hydroelectric Generating Project (Cabinet Gorge) during periods when excess river flows must be diverted over the spillway. Under the terms of the Clark Fork Settlement Agreement as incorporated in Avista Corp.'s FERC license for the Clark Fork Project, Avista Corp. has worked in consultation with agencies, tribes and other stakeholders to address this issue. In the second quarter of 2011, the Company completed preliminary feasibility assessments for several alternative abatement measures. In 2012, Avista Corp., with the approval of the Clark Fork Management Committee (created under the Clark Fork Settlement Agreement), moved forward to test one of the alternatives by constructing a spill crest modification on a single spill gate. Based on testing in 2013, the modification appears to provide significant Total Dissolved Gas reduction. Ongoing design improvements have been made, and the Company expects to continue spill crest modifications over the next several years, in ongoing consultation with key stakeholders. The Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to this issue.
	Fish Passage at Cabinet Gorge and Noxon Rapids
	In 1999, the United States Fish and Wildlife Service (USFWS) listed bull trout as threatened under the Endangered Species Act. The Clark Fork Settlement Agreement describes programs intended to help restore bull trout populations in the project area. Using the concept of adaptive management and working closely with the USFWS, the Company evaluated the feasibility of fish passage at Cabinet Gorge and Noxon Rapids. The results of these studies led, in part, to the decision to move forward with development of permanent facilities, among other bull trout enhancement efforts. Fishway designs for Cabinet Gorge are still being finalized. Construction cost estimates and schedules will be developed after several remaining issues are resolved, related to Montana's approval of fish transport from Idaho and expected minimum discharge requirements. Fishway design for Noxon Rapids has also been initiated, and is still in early stages.
	In January 2010, the USFWS revised its 2005 designation of critical habitat for the bull trout to include the lower Clark Fork River as critical habitat. The Company believes its ongoing efforts through the Clark Fork Settlement Agreement continue to effectively address issues related to bull trout. The Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to fish passage at Cabinet Gorge and Noxon Rapids.
	Kettle Falls Generation Station - Diesel Spill Investigation and Remediation
	On December 24, 2013, the Company's operations staff at the Kettle Falls Generation Station discovered that approximately 10,000 gallons of diesel fuel had leaked underground from the piping system used to fuel heavy equipment. Avista Corp. made all proper agency notifications and worked closely with the Washington State Department of Ecology (Ecology) during the spill response and investigation phase. The Company installed down gradient monitoring wells and there is no indication that ground or surface water is threatened by the spill.
	The Company plans to implement a voluntary cleanup action and there is no indication from Ecology that Ecology is considering any enforcement action. The Company is developing a request for proposal for the most effective remediation system.
	As of March 31, 2014, the Company has recorded an estimated remediation liability and the Company will continue to monitor the remediation activities and will adjust any estimated remediation liability if necessary as new information is obtained. The Company does not expect that this matter will have a material effect on its financial condition, results of operations or cash flows.
	Collective Bargaining Agreements
	The Company’s collective bargaining agreement with the International Brotherhood of Electrical Workers represents approximately 45 percent of all of Avista Utilities’ employees. The agreement with the local union in Washington and Idaho representing the majority (approximately 90 percent) of the bargaining unit employees expired in March 2014. A new three-year agreement in Oregon, which covers approximately 50 employees, was approved in April 2014. Negotiations are currently ongoing with respect to the expired labor agreement in Washington and Idaho and the Company does not expect any disruption to its operations.
	Other Contingencies
	In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes that any ultimate liability arising from these actions will not have a material impact on its financial condition, results of operations or cash flows. It is possible that a change could occur in the Company’s estimates of the probability or amount of a liability being incurred. Such a change, should it occur, could be significant.

Information_By_Business_Segmen

Information By Business Segments	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Information by Business Segments	'
	INFORMATION BY BUSINESS SEGMENTS
	The business segment presentation reflects the basis used by the Company's management to analyze performance and determine the allocation of resources. The Company's management evaluates performance based on income (loss) from operations before income taxes as well as net income (loss) attributable to Avista Corp. shareholders. The accounting policies of the segments are the same as those described in the summary of significant accounting policies. Avista Utilities' business is managed based on the total regulated utility operation. Ecova is a provider of facility information and cost management services for multi-site customers throughout North America. The Other category, which is not a reportable segment, includes Spokane Energy, other investments and operations of various subsidiaries, as well as certain other operations of Avista Capital.
	The following table presents information for each of the Company’s business segments (dollars in thousands):
		Avista		Ecova		Other			Total		Intersegment			Total
		Utilities							Non-Utility		Eliminations (1)
	For the three months ended March 31, 2014:
	Operating revenues	$	437,574	$	44,384	$	9,454		$	53,838	$	(450	)	$	490,962
	Resource costs	220,497		—		—			—		—			220,497
	Other operating expenses	67,337		37,877		9,833			47,710		(450		)	114,597
	Depreciation and amortization	30,726		3,709		147			3,856		—			34,582
	Income (loss) from operations	90,868		2,798		(526		)	2,272		—			93,140
	Interest expense (2)	18,546		340		397			737		(88		)	19,195
	Income taxes	27,620		894		(338		)	556		—			28,176
	Net income (loss) attributable to Avista Corporation shareholders	47,996		1,111		(608		)	503		—			48,499
	Capital expenditures	59,725		3,883		46			3,929		—			63,654
	For the three months ended March 31, 2013:
	Operating revenues	$	431,577	$	42,407	$	9,372		$	51,779	$	(450	)	$	482,906
	Resource costs	229,630		—		—			—		—			229,630
	Other operating expenses	65,444		35,990		9,795			45,785		(450		)	110,779
	Depreciation and amortization	27,935		3,493		190			3,683		—			31,618
	Income (loss) from operations	82,751		2,924		(613		)	2,311		—			85,062
	Interest expense (2)	18,770		444		673			1,117		(77		)	19,810
	Income taxes	24,780		984		(528		)	456		—			25,236
	Net income (loss) attributable to Avista Corporation shareholders	42,250		1,198		(1,107		)	91		—			42,341
	Capital expenditures	70,645		794		25			819		—			71,464
	Total Assets:
	As of March 31, 2014:	$	3,893,474	$	344,828	$	77,776		$	422,604	$	—		$	4,316,078
	As of December 31, 2013:	$	3,940,998	$	339,643	$	81,282		$	420,925	$	—		$	4,361,923
	-1	Intersegment eliminations reported as operating revenues and resource costs represent intercompany purchases and sales of electric capacity and energy. Intersegment eliminations reported as interest expense represent intercompany interest.
	-2	Including interest expense to affiliated trusts.

Summary_Of_Significant_Account1

Summary Of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Dividends [Policy Text Block]	'
	Dividends
	The payment of dividends on common stock could be limited by:
	•	certain covenants applicable to preferred stock (when outstanding) contained in the Company’s Restated Articles of Incorporation, as amended (currently there are no preferred shares outstanding),
	•	certain covenants applicable to the Company's outstanding long-term debt and committed line of credit agreements, and
	•	the hydroelectric licensing requirements of section 10(d) of the FPA.
	Under the covenant applicable to the Company's committed line of credit agreement, which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” to be greater than 65 percent at any time, the amount of retained earnings available for dividends at March 31, 2014 was limited to approximately $342.9 million.
Appropriated Retained Earnings [Policy Text Block]	'
	Appropriated Retained Earnings
	In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for any earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. The rate of return on investment is specified in the various hydroelectric licensing agreements for the Clark Fork River and Spokane River. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company calculates the earnings in excess of the specified rate of return on an annual basis. The appropriated retained earnings amounts included in retained earnings were as follows as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Appropriated retained earnings	$	9,714			$	9,714
Nature Of Business	'
	Nature of Business
	Avista Corporation is an energy company engaged in the generation, transmission and distribution of electricity and distribution of natural gas, as well as other energy-related businesses. Avista Utilities is an operating division of Avista Corp., comprising the regulated utility operations. Avista Utilities provides electric distribution and transmission, as well as natural gas distribution, services in parts of eastern Washington and northern Idaho. Avista Utilities also provides natural gas distribution service in parts of northeastern and southwestern Oregon. Avista Utilities has generating facilities in Washington, Idaho, Oregon and Montana. The Company also supplies electricity to a small number of customers in Montana, most of whom are employees who operate one of the Montana generating facilities. Avista Capital, Inc. (Avista Capital), a wholly owned subsidiary of Avista Corp., is the parent company of all of the subsidiary companies in the non-utility businesses, except Spokane Energy, LLC (Spokane Energy). Avista Capital’s subsidiaries include Ecova, Inc. (Ecova), an 80.2 percent owned subsidiary as of March 31, 2014. Ecova is a provider of energy efficiency and other facility information and cost management programs and services for multi-site customers and utilities throughout North America. See Note 12 for business segment information.
Basis Of Reporting	'
	Basis of Reporting
	The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries, including Ecova and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants.
Taxes Other Than Income Taxes	'
	Taxes Other Than Income Taxes
	Taxes other than income taxes include state excise taxes, city occupational and franchise taxes, real and personal property taxes and certain other taxes not based on net income. These taxes are generally based on revenues or the value of property. Utility related taxes collected from customers (primarily state excise taxes and city utility taxes) are recorded as operating revenue and expense and totaled the following amounts for the three months ended March 31 (dollars in thousands):
		2014				2013
	Utility taxes	$	19,738			$	17,906
Other Income - Net	'
	Other Income-Net
	Other Income-net consisted of the following items for the three months ended March 31 (dollars in thousands):
		2014				2013
	Interest income	$	(274	)		$	(258	)
	Interest income on regulatory deferrals	(44		)		(13		)
	Equity-related AFUDC	(2,034		)		(1,391		)
	Net loss on investments	40				398
	Other income	(239		)		(881		)
	Total	$	(2,551	)		$	(2,145	)
Materials And Supplies, Fuel Stock And Natural Gas Stored	'
	Materials and Supplies, Fuel Stock and Natural Gas Stored
	Inventories of materials and supplies, fuel stock and natural gas stored 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 March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Materials and supplies	$	29,158			$	28,747
	Fuel stock	3,639				3,170
	Natural gas stored	7				13,029
	Total	$	32,804			$	44,946
Investments And Funds Held For Clients And Client Fund Obligations	'
	Investments and Funds Held for Clients and Client Fund Obligations
	In connection with the bill paying services, Ecova collects funds from its clients and remits the funds to the appropriate utility or other service provider. Some of the funds collected are invested by Ecova and classified as investments and funds held for clients, and a related liability for client fund obligations is recorded. Investments and funds held for clients include cash and cash equivalent investments, money market funds and investment securities classified as available for sale. Ecova does not invest the funds directly for the clients' benefit; therefore, Ecova bears the risk of loss associated with the investments. Investments and funds held for clients as of March 31, 2014 are as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	13,618			$	—			$	13,618
	Money market funds	23,034				—				23,034
	Securities available for sale:
	U.S. government agency	55,638				(1,311		)		54,327
	Municipal	3,086				23				3,109
	Corporate fixed income – industrial	752				11				763
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	60,476				(1,277		)		59,199
	Total investments and funds held for clients	$	97,128			$	(1,277	)		$	95,851
	Investments and funds held for clients as of December 31, 2013 are as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	16,147			$	—			$	16,147
	Money market funds	11,180				—				11,180
	Securities available for sale:
	U.S. government agency	63,633				(2,555		)		61,078
	Municipal	3,497				21				3,518
	Corporate fixed income – financial	3,000				—				3,000
	Corporate fixed income – industrial	753				12				765
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	71,883				(2,522		)		69,361
	Total investments and funds held for clients	$	99,210			$	(2,522	)		$	96,688
	-1	Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.
	Investments and funds held for clients are classified as a current asset since these funds are held for the purpose of satisfying the client fund obligations. As of March 31, 2014 and December 31, 2013, approximately 94 percent and 95 percent of the investment portfolio, respectively, were rated AA-, Aa3 and higher by nationally recognized statistical rating organizations. All fixed income securities were rated as investment grade as of March 31, 2014 and December 31, 2013.
	Ecova management reviews its investments continuously for indicators of other-than-temporary impairment. To make this determination, management employs a methodology that considers available quantitative and qualitative evidence in evaluating potential impairment of its investments. If the cost of an investment exceeds its fair value, management evaluates, among other factors, general market conditions, credit quality of instrument issuers, the length of time and extent to which the fair value is less than cost, and whether it has plans to sell the security or it is more-likely-than not that the Company will be required to sell the security before recovery. Management also considers specific adverse conditions related to the financial health of and specific prospects for the issuer as well as other cash flow factors. Once a decline in fair value is determined to be other-than-temporary, an impairment charge is recorded in earnings and a new cost basis in the investment is established. Based on management’s analysis, securities available for sale do not meet the criteria for other-than-temporary impairment as of March 31, 2014 or December 31, 2013.
	The following is a summary of the disposition of available-for-sale securities for the three months ended March 31 (dollars in thousands):
		2014				2013
	Proceeds from sales, maturities and calls	$	11,403			$	7,000
	Gross realized gains	3				2
	Gross realized losses	—				—
	Contractual maturities of securities available for sale as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Due within 1 year				After 1 but within 5 years				After 5 but within 10 years			After 10 years		Total
	31-Mar-14	$	2,235			$	10,508			$	43,460		$	2,996	$	59,199
	31-Dec-13	5,382				12,745				48,310			2,924		69,361
	Actual maturities may differ due to call or prepayment rights and the effective maturity was 2.9 years as of March 31, 2014 and 3.0 years as of December 31, 2013.
Goodwill	'
	Goodwill
	Goodwill arising from acquisitions represents the excess of the purchase price over the estimated fair value of net assets acquired. The Company evaluates goodwill for impairment using a combination of the discounted cash flow model and a market approach on at least an annual basis or more frequently if impairment indicators arise. The Company completed its annual evaluation of goodwill for potential impairment as of December 31, 2013 for Ecova and as of November 30, 2013 for the other businesses and determined that goodwill was not impaired at that time.
	The carrying amount of goodwill as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Ecova				Other				Accumulated			Total
										Impairment
										Losses
	31-Mar-14	$	71,011			$	12,979			$	(7,733	)	$	76,257
	31-Dec-13	$	71,011			$	12,979			$	(7,733	)	$	76,257
	There have been no acquisitions or adjustments to goodwill during the three months ended March 31, 2014. Accumulated impairment losses are attributable to the other businesses.
Other Intangibles	'
	Intangible Assets
	Amortization expense related to Intangible Assets was as follows for the three months ended March 31 (dollars in thousands):
		2014				2013
	Intangible asset amortization	$	2,776			$	2,579
	The following table details the estimated amortization expense related to Intangible Assets for each of the next five years ending December 31 (dollars in thousands):
		Remaining
		2014				2015				2016			2017		2018
	Estimated amortization expense	$	7,863			$	8,818			$	7,697		$	6,887	$	4,100
	The gross carrying amount and accumulated amortization of Intangible Assets as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Estimated		March 31,				December 31,
		Useful Lives		2014				2013
	Client relationships	2 - 12 years		$	33,562			$	33,562
	Software development costs	3 - 7 years		41,146				39,327
	Other	1 - 10 years		3,312				3,321
	Total intangible assets			78,020				76,210
	Client relationships accumulated amortization			(13,347		)		(12,336		)
	Software development costs accumulated amortization			(23,437		)		(21,861		)
	Other accumulated amortization			(2,626		)		(2,437		)
	Total accumulated amortization			(39,410		)		(36,634		)
	Total intangible assets - net			$	38,610			$	39,576
	As of March 31, 2014 and December 31, 2013, all of the intangible assets reported above are associated with Ecova.
Derivative Assets And Liabilities	'
	Derivative Assets and Liabilities
	Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. In certain defined conditions, a derivative may be specifically designated as a hedge for a particular exposure. The accounting for a derivative depends on the intended use of such derivative and the resulting designation.
	The Washington Utilities and Transportation Commission (UTC) and the Idaho Public Utilities Commission (IPUC) issued accounting orders authorizing Avista Utilities to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Utilities to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the Energy Recovery Mechanism (ERM) in Washington, the Power Cost Adjustment (PCA) mechanism in Idaho, and periodic general rates cases. Regulatory assets are assessed regularly and are probable for recovery through future rates.
	Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts that are not considered derivatives are accounted for on the accrual basis until they are settled or realized, unless there is a decline in the fair value of the contract that is determined to be other-than-temporary.
Fair Value Measurements	'
	Fair Value Measurements
	Fair value represents the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Energy commodity derivative assets and liabilities, investments and funds held for clients, deferred compensation assets, as well as derivatives related to interest rate swap agreements and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 9 for the Company’s fair value disclosures.
Regulatory Deferred Charges And Credits	'
	Regulatory Deferred Charges and Credits
	The Company prepares its condensed consolidated financial statements in accordance with regulatory accounting practices because:
	•	rates for regulated services are established by or subject to approval by independent third-party regulators,
	•	the regulated rates are designed to recover the cost of providing the regulated services, and
	•	in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs.
	Regulatory accounting practices require that certain costs and/or obligations (such as incurred power and natural gas costs not currently included in rates, but expected to be recovered or refunded in the future) are reflected as deferred charges or credits on the Condensed Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Condensed Consolidated Statements of Income until the period during which matching revenues are recognized. If at some point in the future the Company determines that it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be:
	•	required to write off its regulatory assets, and
	•	precluded from the future deferral of costs not recovered through rates at the time such costs are incurred, even if the Company expected to recover such costs in the future.
Redeemable Noncontrolling Interests [Policy Text Block]	'
	Redeemable Noncontrolling Interests
	Certain option holders of Ecova have the right to put their shares back to Ecova at their discretion during an annual put window. Stock options and other outstanding redeemable stock are valued at their maximum redemption amount which is equal to their intrinsic value (fair value less exercise price).
Contingencies	'
	Contingencies
	The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable that a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses losses that do not meet these conditions for accrual, if there is a reasonable possibility that a loss may be incurred.
Accumulated Other Comprehensive Loss [Policy Text Block]	'
	Accumulated Other Comprehensive Loss
	Accumulated other comprehensive loss, net of tax, consisted of the following as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $(2,220) and $(2,280), respectively	$	(4,122	)		$	(4,233	)
	Unrealized loss on securities available for sale - net of taxes of $(474) and $(936), respectively	(803		)		(1,586		)
	Total accumulated other comprehensive loss	$	(4,925	)		$	(5,819	)
	The following table details the reclassifications out of accumulated other comprehensive loss by component for the three months ended March 31 (dollars in thousands):
			Amounts Reclassified from Accumulated Other Comprehensive Loss
	Details about Accumulated Other Comprehensive Loss Components		2014				2013				Affected Line Item in Statement of Income
	Realized gains on investment securities		$	3			$	2			Other income-net
			3				2				Total before tax
			(1		)		(1		)		Tax expense
			$	2			$	1			Net of tax
	Amortization of defined benefit pension items
	Amortization of net loss		$	(1,952	)		$	(4,891	)		(a)
	Adjustment due to effects of regulation		1,782				4,608				(a)
			(170		)		(283		)		Total before tax
			59				99				Tax benefit
			$	(111	)		$	(184	)		Net of tax
	(a)	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).

Summary_Of_Significant_Account2

Summary Of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Appropriated Retained Earnings [Table Text Block]	'
	The appropriated retained earnings amounts included in retained earnings were as follows as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Appropriated retained earnings	$	9,714			$	9,714
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	Accumulated other comprehensive loss, net of tax, consisted of the following as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $(2,220) and $(2,280), respectively	$	(4,122	)		$	(4,233	)
	Unrealized loss on securities available for sale - net of taxes of $(474) and $(936), respectively	(803		)		(1,586		)
	Total accumulated other comprehensive loss	$	(4,925	)		$	(5,819	)
Reclassifications Out of Accumulated Other Comprehensive Loss by Component	'
	The following table details the reclassifications out of accumulated other comprehensive loss by component for the three months ended March 31 (dollars in thousands):
			Amounts Reclassified from Accumulated Other Comprehensive Loss
	Details about Accumulated Other Comprehensive Loss Components		2014				2013				Affected Line Item in Statement of Income
	Realized gains on investment securities		$	3			$	2			Other income-net
			3				2				Total before tax
			(1		)		(1		)		Tax expense
			$	2			$	1			Net of tax
	Amortization of defined benefit pension items
	Amortization of net loss		$	(1,952	)		$	(4,891	)		(a)
	Adjustment due to effects of regulation		1,782				4,608				(a)
			(170		)		(283		)		Total before tax
			59				99				Tax benefit
			$	(111	)		$	(184	)		Net of tax
	(a)	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).
Utility Taxes	'
	Utility related taxes collected from customers (primarily state excise taxes and city utility taxes) are recorded as operating revenue and expense and totaled the following amounts for the three months ended March 31 (dollars in thousands):
		2014				2013
	Utility taxes	$	19,738			$	17,906
Other Income - Net	'
	Other Income-net consisted of the following items for the three months ended March 31 (dollars in thousands):
		2014				2013
	Interest income	$	(274	)		$	(258	)
	Interest income on regulatory deferrals	(44		)		(13		)
	Equity-related AFUDC	(2,034		)		(1,391		)
	Net loss on investments	40				398
	Other income	(239		)		(881		)
	Total	$	(2,551	)		$	(2,145	)
Materials And Supplies Fuel Stock And Natural Gas Stored	'
	Inventories of materials and supplies, fuel stock and natural gas stored 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 March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,				December 31,
		2014				2013
	Materials and supplies	$	29,158			$	28,747
	Fuel stock	3,639				3,170
	Natural gas stored	7				13,029
	Total	$	32,804			$	44,946
Investments And Funds Held For Clients	'
	Investments and funds held for clients as of March 31, 2014 are as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	13,618			$	—			$	13,618
	Money market funds	23,034				—				23,034
	Securities available for sale:
	U.S. government agency	55,638				(1,311		)		54,327
	Municipal	3,086				23				3,109
	Corporate fixed income – industrial	752				11				763
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	60,476				(1,277		)		59,199
	Total investments and funds held for clients	$	97,128			$	(1,277	)		$	95,851
	Investments and funds held for clients as of December 31, 2013 are as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	16,147			$	—			$	16,147
	Money market funds	11,180				—				11,180
	Securities available for sale:
	U.S. government agency	63,633				(2,555		)		61,078
	Municipal	3,497				21				3,518
	Corporate fixed income – financial	3,000				—				3,000
	Corporate fixed income – industrial	753				12				765
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	71,883				(2,522		)		69,361
	Total investments and funds held for clients	$	99,210			$	(2,522	)		$	96,688
	-1	Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.
Contractual Maturities Of Securities Available For Sale	'
	Contractual maturities of securities available for sale as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Due within 1 year				After 1 but within 5 years				After 5 but within 10 years			After 10 years		Total
	31-Mar-14	$	2,235			$	10,508			$	43,460		$	2,996	$	59,199
	31-Dec-13	5,382				12,745				48,310			2,924		69,361
Goodwill	'
	The carrying amount of goodwill as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Ecova				Other				Accumulated			Total
										Impairment
										Losses
	31-Mar-14	$	71,011			$	12,979			$	(7,733	)	$	76,257
	31-Dec-13	$	71,011			$	12,979			$	(7,733	)	$	76,257
Other Intangible Amortization	'
	Amortization expense related to Intangible Assets was as follows for the three months ended March 31 (dollars in thousands):
		2014				2013
	Intangible asset amortization	$	2,776			$	2,579
Future Estimated Amortization Expense	'
	The following table details the estimated amortization expense related to Intangible Assets for each of the next five years ending December 31 (dollars in thousands):
		Remaining
		2014				2015				2016			2017		2018
	Estimated amortization expense	$	7,863			$	8,818			$	7,697		$	6,887	$	4,100
Accumulated Amortization Of Other Intangibles	'
	The gross carrying amount and accumulated amortization of Intangible Assets as of March 31, 2014 and December 31, 2013 are as follows (dollars in thousands):
		Estimated		March 31,				December 31,
		Useful Lives		2014				2013
	Client relationships	2 - 12 years		$	33,562			$	33,562
	Software development costs	3 - 7 years		41,146				39,327
	Other	1 - 10 years		3,312				3,321
	Total intangible assets			78,020				76,210
	Client relationships accumulated amortization			(13,347		)		(12,336		)
	Software development costs accumulated amortization			(23,437		)		(21,861		)
	Other accumulated amortization			(2,626		)		(2,437		)
	Total accumulated amortization			(39,410		)		(36,634		)
	Total intangible assets - net			$	38,610			$	39,576
Disposition of Available-for-Sale Securities	'
	The following is a summary of the disposition of available-for-sale securities for the three months ended March 31 (dollars in thousands):
		2014				2013
	Proceeds from sales, maturities and calls	$	11,403			$	7,000
	Gross realized gains	3				2
	Gross realized losses	—				—

Derivatives_And_Risk_Managemen1

Derivatives And Risk Management (Tables)	3 Months Ended
	Mar. 31, 2014
Derivative Instruments and Hedges, Assets [Abstract]	'
Energy Commodity Derivatives	'
	The following table presents the underlying energy commodity derivative volumes as of March 31, 2014 that are expected to be delivered in each respective year (in thousands of MWhs and mmBTUs):
		Purchases										Sales
		Electric Derivatives					Gas Derivatives					Electric Derivatives					Gas Derivatives
	Year	Physical (1)		Financial (1)			Physical (1)			Financial (1)		Physical (1)		Financial (1)			Physical (1)			Financial (1)
		MWH		MWH			mmBTUs			mmBTUs		MWH		MWH			mmBTUs			mmBTUs
	2014	725		1,768			18,282			110,762		688		2,522			3,021			87,043
	2015	559		1,461			4,973			82,825		222		2,566			1,490			58,210
	2016	397		948			2,505			51,950		256		1,634			910			41,490
	2017	397		—			675			—		286		—			—			—
	2018	397		—			—			—		286		—			—			—
	Thereafter	235		—			—			—		158		—			—			—
	-1	Physical transactions represent commodity transactions where Avista Utilities will take delivery of either electricity or natural gas and financial transactions represent derivative instruments with no physical delivery, such as futures, swaps or options.
Foreign Currency Exchange Contracts	'
	The following table summarizes the foreign currency hedges that the Company has entered into as of March 31, 2014 and December 31, 2013 (dollars in thousands):
		March 31,			December 31,
		2014			2013
	Number of contracts	23			23
	Notional amount (in United States dollars)	$	13,128		$	8,631
	Notional amount (in Canadian dollars)	14,596			9,191
Interest Rate Swap Agreements	'
	The following table summarizes the interest rate swaps that the Company has entered into as of March 31, 2014 and December 31, 2013 (dollars in thousands):
	Balance Sheet Date		Number of Contracts	Notional Amount				Mandatory Cash Settlement Date
	March 31, 2014		2	$	50,000			2014
			3	60,000				2015
			3	60,000				2016
			2	30,000				2017
			5	115,000				2018
	December 31, 2013		2	50,000				2014
			2	45,000				2015
			2	40,000				2016
			1	15,000				2017
			4	95,000				2018
Derivative Instruments Summary	'
	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of March 31, 2014 (in thousands):
				Fair Value
	Derivative		Balance Sheet Location	Gross				Gross			Collateral			Net Asset				Gross Assets Not Offset			Gross Liabilities Not Offset			Net Asset (Liability)
				Asset				Liability			Netting			(Liability)
														in Balance
														Sheet
	Foreign currency contracts		Other current assets	$	47			$	(30	)	$	—		$	17			$	—		$	—		$	17
	Interest rate contracts		Other current assets	10,619				—			—			10,619				—			—			10,619
	Interest rate contracts		Other property and investments - net	10,641				(3,097		)	—			7,544				—			—			7,544
	Interest rate contracts		Other non-current liabilities and deferred credits	—				(8,906		)	2,210			(6,696		)		—			—			(6,696		)
	Commodity contracts (1)		Current utility energy commodity derivative assets	58,483				(41,846		)	(2,712		)	13,925				—			(158		)	13,767
	Commodity contracts (1)		Non-current utility energy commodity derivative assets	31,510				(27,965		)	—			3,545				—			—			3,545
	Commodity contracts (1)		Current utility energy commodity derivative liabilities	1,415				(4,775		)	—			(3,360		)		—			158			(3,202		)
	Commodity contracts (1)		Other non-current liabilities and deferred credits	72				(15,271		)	—			(15,199		)		—			—			(15,199		)
	Total derivative instruments recorded on the balance sheet			$	112,787			$	(101,890	)	$	(502	)	$	10,395			$	—		$	—		$	10,395
	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2013 (in thousands):
				Fair Value
	Derivative		Balance Sheet Location	Gross				Gross			Collateral			Net Asset				Gross Assets Not Offset			Gross Liabilities Not Offset			Net Asset (Liability)
				Asset				Liability			Netting			(Liability)
														in Balance
														Sheet
	Foreign currency contracts		Other current assets	$	7			$	(6	)	$	—		$	1			$	—		$	—		$	1
	Interest rate contracts		Other current assets	13,968				—			—			13,968				—			—			13,968
	Interest rate contracts		Other property and investments - net	19,575				—			—			19,575				—			—			19,575
	Commodity contracts (1)		Current utility energy commodity derivative assets	7,416				(4,394		)	—			3,022				—			—			3,022
	Commodity contracts (1)		Non-current utility energy commodity derivative assets	7,610				(6,756		)	—			854				—			—			854
	Commodity contracts (1)		Current utility energy commodity derivative liabilities	23,455				(37,306		)	2,976			(10,875		)		—			—			(10,875		)
	Commodity contracts (1)		Other non-current liabilities and deferred credits	17,101				(41,213		)	5,756			(18,356		)		—			—			(18,356		)
	Total derivative instruments recorded on the balance sheet			$	89,132			$	(89,675	)	$	8,732		$	8,189			$	—		$	—		$	8,189
	-1	Avista Corp. has a master netting agreement that governs the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allows for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performs cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. does not perform cross-affiliate netting because the Company believes that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 are not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there is no additional netting which requires disclosure for that period.

Pension_Plans_And_Other_Postre1

Pension Plans And Other Postretirement Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2014
Components of Net Periodic Benefit Cost	'
		Pension Benefits						Other Post-retirement Benefits
		2014			2013			2014			2013
	Three months ended March 31:
	Service cost	$	5,018		$	4,743		$	974		$	1,032
	Interest cost	6,706			5,978			1,353			1,390
	Expected return on plan assets	(8,110		)	(6,900		)	(472		)	(400		)
	Amortization of prior service cost	6			75			(43		)	(37		)
	Net loss recognition	1,157			3,547			826			1,521
	Net periodic benefit cost	$	4,777		$	7,443		$	2,638		$	3,506

Committed_Lines_of_Credit_Tabl

Committed Lines of Credit (Tables)	3 Months Ended
	Mar. 31, 2014
Schedule Of Borrowings Outstanding And Letters Of Credit	'
		March 31,			December 31,
		2014			2013
	Borrowings outstanding at end of period	$	111,000		$	171,000
	Letters of credit outstanding at end of period	$	9,614		$	27,434
	Average interest rate on borrowings at end of period	0.93		%	1.02		%
Ecova [Member]	'
Schedule Of Borrowings Outstanding And Letters Of Credit	'
		March 31,			December 31,
		2014			2013
	Borrowings outstanding at end of period	$	42,000		$	46,000
	Average interest rate on borrowings at end of period	2.16		%	2.17		%

LongTerm_Debt_Tables

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Long-term Debt, Unclassified [Abstract]	'
Long-term Debt Outstanding	'
	Maturity			Interest	March 31,			December 31,
	Year		Description	Rate	2014			2013
	2016		First Mortgage Bonds	0.84%	$	90,000		$	90,000
	2018		First Mortgage Bonds	5.95%	250,000			250,000
	2018		Secured Medium-Term Notes	7.39%-7.45%	22,500			22,500
	2019		First Mortgage Bonds	5.45%	90,000			90,000
	2020		First Mortgage Bonds	3.89%	52,000			52,000
	2022		First Mortgage Bonds	5.13%	250,000			250,000
	2023		Secured Medium-Term Notes	7.18%-7.54%	13,500			13,500
	2028		Secured Medium-Term Notes	6.37%	25,000			25,000
	2032		Secured Pollution Control Bonds (1)	-1	66,700			66,700
	2034		Secured Pollution Control Bonds (1)	-1	17,000			17,000
	2035		First Mortgage Bonds	6.25%	150,000			150,000
	2037		First Mortgage Bonds	5.70%	150,000			150,000
	2040		First Mortgage Bonds	5.55%	35,000			35,000
	2041		First Mortgage Bonds	4.45%	85,000			85,000
	2047		First Mortgage Bonds	4.23%	80,000			80,000
			Total secured long-term debt		1,376,700			1,376,700
			Other long-term debt and capital leases		4,561			4,630
			Settled interest rate swaps (2)		(23,413		)	(23,560		)
			Unamortized debt discount		(1,246		)	(1,287		)
			Total		1,356,602			1,356,483
			Secured Pollution Control Bonds held by Avista Corporation (1)		(83,700		)	(83,700		)
			Current portion of long-term debt		(372		)	(358		)
			Total long-term debt		$	1,272,530		$	1,272,425
	-1	In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.
	-2	Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.

Fair_Value_Tables

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]	'
Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]	'
			Fair Value (Net) at
			March 31, 2014				Valuation Technique		Unobservable		Range
									Input
	Power exchange agreement		$	(13,624	)		Surrogate facility		O&M charges		$30.18-$53.90/MWh (1)
							pricing		Escalation factor		3% - 2014 to 2019
									Transaction volumes		396,984 - 397,116 MWhs
	Power option agreement		(428		)		Black-Scholes-		Strike price		$56.53/MWh - 2016
							Merton				$69.98/MWh - 2015
									Delivery volumes		128,278 - 286,307 MWhs
									Volatility rates		0.20 (2)
	Natural gas exchange		(2,418		)		Internally derived		Forward purchase		$3.66 - $4.45/mmBTU
	agreement						weighted average		prices
							cost of gas		Forward sales prices		$4.54 - $5.23/mmBTU
									Purchase volumes		280,000 - 310,000 mmBTUs
									Sales volumes		279,990 - 310,000 mmBTUs
Carrying Value and Estimated Fair Value of Financial Instruments	'
		March 31, 2014								December 31, 2013
		Carrying				Estimated				Carrying			Estimated
		Value				Fair Value				Value			Fair Value
	Long-term debt (Level 2)	$	951,000			$	1,080,124			$	951,000		$	1,054,512
	Long-term debt (Level 3)	342,000				345,980				342,000			329,581
	Nonrecourse long-term debt (Level 3)	13,872				14,323				17,838			18,636
	Long-term debt to affiliated trusts (Level 3)	51,547				37,052				51,547			37,114
Fair Value of Assets And Liabilities Measured on Recurring Basis	'
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	31-Mar-14
	Assets:
	Energy commodity derivatives	$	—			$	91,090			$	—		$	(73,620	)	$	17,470
	Level 3 energy commodity derivatives:
	Power exchange agreement	—				—				390			(390		)	—
	Foreign currency derivatives	—				47				—			(30		)	17
	Interest rate swaps	—				21,260				—			(3,097		)	18,163
	Investments and funds held for clients:
	Money market funds	23,034				—				—			—			23,034
	Securities available for sale:
	U.S. government agency	—				54,327				—			—			54,327
	Municipal	—				3,109				—			—			3,109
	Corporate fixed income – industrial	—				763				—			—			763
	Certificate of deposits	—				1,000				—			—			1,000
	Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
	Deferred compensation assets:
	Fixed income securities (2)	1,906				—				—			—			1,906
	Equity securities (2)	6,475				—				—			—			6,475
	Total	$	33,015			$	171,596			$	390		$	(77,137	)	$	127,864
	Liabilities:
	Energy commodity derivatives	$	—			$	72,997			$	—		$	(70,908	)	$	2,089
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				2,418			—			2,418
	Power exchange agreement	—				—				14,014			(390		)	13,624
	Power option agreement	—				—				428			—			428
	Foreign currency derivatives	—				30				—			(30		)	—
	Interest rate swaps	—				12,003				—			(5,307		)	6,696
	Total	$	—			$	85,030			$	16,860		$	(76,635	)	$	25,255
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	31-Dec-13
	Assets:
	Energy commodity derivatives	$	—			$	55,243			$	—		$	(51,367	)	$	3,876
	Level 3 energy commodity derivatives:
	Power exchange agreement	—				—				339			(339		)	—
	Foreign currency derivatives	—				7				—			(6		)	1
	Interest rate swaps	—				33,543				—			—			33,543
	Investments and funds held for clients:
	Money market funds	11,180				—				—			—			11,180
	Securities available for sale:
	U.S. government agency	—				61,078				—			—			61,078
	Municipal	—				3,518				—			—			3,518
	Corporate fixed income – financial	—				3,000				—			—			3,000
	Corporate fixed income – industrial	—				765				—			—			765
	Certificate of deposits	—				1,000				—			—			1,000
	Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
	Deferred compensation assets:
	Fixed income securities (2)	1,960				—				—			—			1,960
	Equity securities (2)	6,470				—				—			—			6,470
	Total	$	21,210			$	158,154			$	339		$	(51,712	)	$	127,991
	Liabilities:
	Energy commodity derivatives	$	—			$	72,895			$	—		$	(60,099	)	$	12,796
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				1,219			—			1,219
	Power exchange agreement	—				—				14,780			(339		)	14,441
	Power option agreement	—				—				775			—			775
	Foreign currency derivatives	—				6				—			(6		)	—
Total	$	—			$	72,901			$	16,774		$	(60,444	)	$	29,231
-1	The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties.
-2	These assets are trading securities and are included in other property and investments-net on the Condensed Consolidated Balance Sheets.
Reconciliation for All Assets Measured At Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)	'
		Natural Gas Exchange Agreement				Power Exchange Agreement				Power Option Agreement			Total
	Three months ended March 31, 2014:
	Balance as of January 1, 2014	$	(1,219	)		$	(14,441	)		$	(775	)	$	(16,435	)
	Total gains or losses (realized/unrealized):
	Included in net income	—				—				—			—
	Included in other comprehensive income	—				—				—			—
	Included in regulatory assets/liabilities (1)	1,849				2,026				347			4,222
	Purchases	—				—				—			—
	Issuance	—				—				—			—
	Settlements	(3,048		)		(1,209		)		—			(4,257		)
	Transfers to/from other categories	—				—				—			—
	Ending balance as of March 31, 2014	$	(2,418	)		$	(13,624	)		$	(428	)	$	(16,470	)
	Three months ended March 31, 2013:
	Balance as of January 1, 2013	$	(2,379	)		$	(18,692	)		$	(1,480	)	$	(22,551	)
	Total gains or losses (realized/unrealized):
	Included in net income	—				—				—			—
	Included in other comprehensive income	—				—				—			—
	Included in regulatory assets/liabilities (1)	750				24				280			1,054
	Purchases	—				—				—			—
	Issuance	—				—				—			—
	Settlements	(362		)		2,205				—			1,843
	Transfers from other categories	—				—				—			—
	Ending balance as of March 31, 2013	$	(1,991	)		$	(16,463	)		$	(1,200	)	$	(19,654	)
	-1	The UTC and the IPUC issued accounting orders authorizing Avista Corp. to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Corp. to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates cases.

Earnings_Per_Common_Share_Attr1

Earnings Per Common Share Attributable To Avista Corporation (Tables)	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Computations Of Earnings Per Share	'
		2014			2013
	Numerator:
	Net income attributable to Avista Corporation shareholders	$	48,499		$	42,341
	Subsidiary earnings adjustment for dilutive securities	(53		)	(43		)
	Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$	48,446		$	42,298
	Denominator:
	Weighted-average number of common shares outstanding-basic	60,122			59,866
	Effect of dilutive securities:
	Performance and restricted stock awards	46			32
	Weighted-average number of common shares outstanding-diluted	60,168			59,898
	Earnings per common share attributable to Avista Corporation shareholders:
	Basic	$	0.81		$	0.71
	Diluted	$	0.81		$	0.71
	There were no shares excluded from the calculation because they were antidilutive.

Information_By_Business_Segmen1

Information By Business Segments (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Information by Business Segments	'
	The following table presents information for each of the Company’s business segments (dollars in thousands):
		Avista		Ecova		Other			Total		Intersegment			Total
		Utilities							Non-Utility		Eliminations (1)
	For the three months ended March 31, 2014:
	Operating revenues	$	437,574	$	44,384	$	9,454		$	53,838	$	(450	)	$	490,962
	Resource costs	220,497		—		—			—		—			220,497
	Other operating expenses	67,337		37,877		9,833			47,710		(450		)	114,597
	Depreciation and amortization	30,726		3,709		147			3,856		—			34,582
	Income (loss) from operations	90,868		2,798		(526		)	2,272		—			93,140
	Interest expense (2)	18,546		340		397			737		(88		)	19,195
	Income taxes	27,620		894		(338		)	556		—			28,176
	Net income (loss) attributable to Avista Corporation shareholders	47,996		1,111		(608		)	503		—			48,499
	Capital expenditures	59,725		3,883		46			3,929		—			63,654
	For the three months ended March 31, 2013:
	Operating revenues	$	431,577	$	42,407	$	9,372		$	51,779	$	(450	)	$	482,906
	Resource costs	229,630		—		—			—		—			229,630
	Other operating expenses	65,444		35,990		9,795			45,785		(450		)	110,779
	Depreciation and amortization	27,935		3,493		190			3,683		—			31,618
	Income (loss) from operations	82,751		2,924		(613		)	2,311		—			85,062
	Interest expense (2)	18,770		444		673			1,117		(77		)	19,810
	Income taxes	24,780		984		(528		)	456		—			25,236
	Net income (loss) attributable to Avista Corporation shareholders	42,250		1,198		(1,107		)	91		—			42,341
	Capital expenditures	70,645		794		25			819		—			71,464
	Total Assets:
	As of March 31, 2014:	$	3,893,474	$	344,828	$	77,776		$	422,604	$	—		$	4,316,078
	As of December 31, 2013:	$	3,940,998	$	339,643	$	81,282		$	420,925	$	—		$	4,361,923
	-1	Intersegment eliminations reported as operating revenues and resource costs represent intercompany purchases and sales of electric capacity and energy. Intersegment eliminations reported as interest expense represent intercompany interest.
	-2	Including interest expense to affiliated trusts.

Summary_Of_Significant_Account3

Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Maximum Dividends Allowed by Debt Covenants	$342,900,000	'	'
Investment Portfolio Percentage, Rated AA-, Aa3 and Higher	94.00%	'	95.00%
Sale and maturity of securities available for sale	$11,403,000	$7,000,000	'
Ecova [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Owners percentage interest	80.20%	'	'
Other Intangible Assets [Member] | Minimum [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Finite-Lived Intangible Asset, Useful Life	'1 year	'	'
Other Intangible Assets [Member] | Maximum [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Finite-Lived Intangible Asset, Useful Life	'10 years	'	'
Software and Software Development Costs [Member] | Minimum [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Finite-Lived Intangible Asset, Useful Life	'3 years	'	'
Software and Software Development Costs [Member] | Maximum [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Finite-Lived Intangible Asset, Useful Life	'7 years	'	'
Customer Relationships [Member] | Minimum [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Finite-Lived Intangible Asset, Useful Life	'2 years	'	'
Customer Relationships [Member] | Maximum [Member]	'	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'	'
Finite-Lived Intangible Asset, Useful Life	'12 years	'	'

Summary_Of_Significant_Account4

Summary Of Significant Accounting Policies (Utility Taxes) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Accounting Policies [Abstract]	'	'
Utility taxes	$19,738	$17,906

Summary_Of_Significant_Account5

Summary Of Significant Accounting Policies (Other Income - Net) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Accounting Policies [Abstract]	'	'
Interest income	($274)	($258)
Interest on regulatory deferrals	-44	-13
Equity-related AFUDC	-2,034	-1,391
Net loss on investments	40	398
Other income	-239	-881
Total	($2,551)	($2,145)

Summary_Of_Significant_Account6

Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Materials and supplies	$29,158	$28,747
Fuel stock	3,639	3,170
Natural gas stored	7	13,029
Total	$32,804	$44,946

Summary_Of_Significant_Account7

Summary Of Significant Accounting Policies (Investments And Funds Held For Customers) (Details) (USD $)	3 Months Ended			12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Available for Sale Securities Debt Effective Maturity	'2 years 329 days		'	'3 years
Proceeds from Sale of Available-for-sale Securities	$11,403		$7,000	'
Cash and Cash Equivalents, Amortized Cost	13,618	[1]	'	16,147	[1]
Cash And Cash Equivalents Unrealized Gain Loss	0		'	0
Money market funds	13,618		'	16,147
Money market funds, Amortized Cost	23,034	[1]	'	11,180	[1]
Money Market Funds, Unrealized Gain Loss	0		'	0
Total securities available for sale, Amortized Cost	60,476	[1]	'	71,883	[1]
Total securities available for sale, Unrealized Gain (Loss)	-1,277		'	-2,522
Total securities available for sale, Fair Value	59,199		'	69,361
Total investments and funds held for clients, Amortized Cost	97,128	[1]	'	99,210	[1]
Total investments and funds held for clients, Unrealized Gain (Loss)	-1,277		'	-2,522
Total investments and funds held for clients, fair value	95,851		'	96,688
U.S. Government Agency [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Amortized Cost	55,638	[1]	'	63,633	[1]
Total securities available for sale, Unrealized Gain (Loss)	-1,311		'	-2,555
Municipal [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Amortized Cost	3,086	[1]	'	3,497	[1]
Total securities available for sale, Unrealized Gain (Loss)	23		'	21
Corporate fixed income - financial [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Amortized Cost	'		'	3,000	[1]
Total securities available for sale, Unrealized Gain (Loss)	'		'	0
Corporate fixed income - industrial [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Amortized Cost	752	[1]	'	753	[1]
Total securities available for sale, Unrealized Gain (Loss)	11		'	12
Certificates of deposits [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Amortized Cost	1,000	[1]	'	1,000	[1]
Total securities available for sale, Unrealized Gain (Loss)	0		'	0
Fair Value, Measurements, Recurring [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Money Market Funds, Fair Value	23,034		'	11,180
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	54,327		'	61,078
Fair Value, Measurements, Recurring [Member] | Municipal [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	3,109		'	3,518
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	'		'	3,000
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	763		'	765
Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	1,000		'	1,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Money Market Funds, Fair Value	23,034		'	11,180
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	54,327		'	61,078
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	3,109		'	3,518
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	'		'	3,000
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	763		'	765
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]	'		'	'
Schedule of Available-for-sale Securities [Line Items]	'		'	'
Total securities available for sale, Fair Value	$1,000		'	$1,000
[1]	(1) Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.

Summary_Of_Significant_Account8

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Disposition of Available-for-Sale Securities) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Disposition of Available for Sale Securities [Abstract]	'	'
Proceeds from Sale of Available-for-sale Securities	$11,403	$7,000
Available-for-sale Securities, Gross Realized Gains	3	2
Available-for-sale Securities, Gross Realized Losses	$0	$0

Summary_Of_Significant_Account9

Summary Of Significant Accounting Policies (Contractual Maturities Of Securities Available For Sale) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Due within 1 year	$2,235	$5,382
After 1 but within 5 years	10,508	12,745
After 5 but within 10 years	43,460	48,310
After 10 years	2,996	2,924
Total securities available for sale, Fair Value	$59,199	$69,361

Recovered_Sheet1

Summary Of Significant Accounting Policies (Goodwill) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance at beginning	$76,257	$76,257
Balance at ending	76,257	76,257
Ecova [Member]	'	'
Balance at beginning	71,011	71,011
Balance at ending	71,011	71,011
Other [Member]	'	'
Balance at beginning	12,979	12,979
Balance at ending	12,979	12,979
Accumulated Impairment Losses [Member]	'	'
Balance at beginning	-7,733	-7,733
Balance at ending	($7,733)	($7,733)

Recovered_Sheet2

Summary Of Significant Accounting Policies (Other Intangible Amortization) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Accounting Policies [Abstract]	'	'
Intangible asset amortization	$2,776	$2,579

Recovered_Sheet3

Summary Of Significant Accounting Policies (Future Estimated Amortization Expense) (Details) (USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'
2014	$7,863
2015	8,818
2016	7,697
2017	6,887
2018	$4,100

Recovered_Sheet4

Summary Of Significant Accounting Policies (Accumulated Amortization Of Other Intangibles) (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

In Thousands, unless otherwise specified

Ecova [Member]

Ecova [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Customer Relationships [Member]

Customer Relationships [Member]

Software and Software Development Costs [Member]

Software and Software Development Costs [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Other Intangible Assets [Member]

Customer Relationships [Member]

Software and Software Development Costs [Member]

Finite-Lived Intangible Assets [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Finite-Lived Intangible Asset, Useful Life

'

'

'

'

'

'

'

'

'

'

'1 year

'2 years

'3 years

Client relationships

$33,562

$33,562

'

'

'

'

'

'

'

'

'

'

'

Software development costs

41,146

39,327

'

'

'

'

'

'

'

'

'

'

'

Other

3,312

3,321

'

'

'

'

'

'

'

'

'

'

'

Total intangible assets

78,020

76,210

'

'

'

'

'

'

'

'

'

'

'

Total accumulated amortization

-39,410

-36,634

'

'

-2,626

-2,437

-13,347

-12,336

-23,437

-21,861

'

'

'

Total intangible assets - net

$38,610

$39,576

$38,610

$39,576

'

'

'

'

'

'

'

'

'

Recovered_Sheet5

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'
Accumulated Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities, Tax	($474)	($936)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans Net Unamortized (Gain) Loss, Tax	-2,220	-2,280
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	4,122	4,233
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-803	-1,586
Accumulated other comprehensive loss	($4,925)	($5,819)

Recovered_Sheet6

Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]	'		'
Other income-net	$239		$881
Tax expense	-28,176		-25,236
Net income	48,981		43,101
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]	'		'
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]	'		'
Other income-net	3		2
Total before tax	3		2
Tax expense	-1		-1
Net income	2		1
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]	'		'
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]	'		'
Total before tax	-170		-283
Tax expense	59		99
Net income	-111		-184
Amortization of net loss	-1,952	[1]	-4,891	[1]
Adjustment due to effects of regulation	$1,782	[1]	$4,608	[1]
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).

Recovered_Sheet7

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Appropriated Retained Earnings) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Appropriated Retained Earnings [Abstract]	'	'
Retained Earnings, Appropriated	$9,714	$9,714

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating revenues	$490,962,000	$482,906,000
Lancaster Power Purchase Agreement [Member]	'	'
Evaluated Power Capacity	270	'
Future contractual obligation	292,000,000	'
Palouse Wind Power Purchase Agreement [Member]	'	'
Evaluated Power Capacity	105	'
Expected power production, in megawatts	40	'
Future contractual obligation	$600,000,000	'
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	'

Business_Acquisitions_Details

Business Acquisitions (Details) (USD $)	3 Months Ended			9 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
	MW		Alaska Energy Resources Company [Member]	Alaska Energy Resources Company [Member]	Alaska Electric Light & Power [Member]	Power purchase agreement [Member]	Hydroelectric Production [Member]	Fossil Fuel Plant [Member]	AEL&P Hydroelectric Production [Member]	Minimum [Member]	Maximum [Member]
					employee	Alaska Electric Light & Power [Member]	Alaska Electric Light & Power [Member]	Alaska Electric Light & Power [Member]	Alaska Electric Light & Power [Member]	Alaska Energy Resources Company [Member]	Alaska Energy Resources Company [Member]
						MW	MW	MW	MW
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Number of Customers	'	'	'	'	16,000	'	'	'	'	'	'
Operating revenues	$490,962,000	$482,906,000	'	'	$42,600,000	'	'	'	'	'	'
Total Rate Base	'	'	'	'	109,000,000	'	'	'	'	'	'
Entity Number of Employees	'	'	'	'	60	'	'	'	'	'	'
Peak electric usage	68	'	'	'	'	'	'	'	'	'	'
Evaluated Power Capacity	'	'	'	'	'	78	102.7	93.9	24.7	'	'
Merger Consideration - Total	'	'	170,000,000	'	'	'	'	'	'	'	'
Business Combination Equity Consideration Share Price	'	'	'	'	'	'	'	'	'	$21.48	$34.30
Representative Reimbursement Amount	'	'	500,000	'	'	'	'	'	'	'	'
Business Combination, Acquisition Related Costs	'	'	$500,000	$2,100,000	'	'	'	'	'	'	'

Derivatives_And_Risk_Managemen2

Derivatives And Risk Management (Narrative) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]	'	'
Secured Debt	$1,376,700,000	$1,376,700,000
Cash deposited as collateral	2,100,000	26,100,000
Cash held as collateral	2,700,000	0
Derivative, Fair Value, Amount Offset Against Collateral, Net	-502,000	8,732,000
Liability position at aggregate fair value	3,800,000	13,300,000
Collateral agreements	2,900,000	12,600,000
First Mortgage [Member] | 2041 [Member]	'	'
Derivative [Line Items]	'	'
Secured Debt	85,000,000	85,000,000
Commodity Contracts [Member]	'	'
Derivative [Line Items]	'	'
Letters of credit outstanding	2,500,000	20,300,000
Interest Rate Swap [Member]	'	'
Derivative [Line Items]	'	'
Cash deposited as collateral	$2,200,000	'

Derivatives_And_Risk_Managemen3

Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	3 Months Ended
	Mar. 31, 2014
	frequency
Sales [Member] | Physical [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	688,000	[1]
2015	222,000	[1]
2016	256,000	[1]
2017	286,000	[1]
2018	286,000	[1]
Thereafter	158,000	[1]
Sales [Member] | Physical [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	3,021,000	[1]
2015	1,490,000	[1]
2016	910,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Sales [Member] | Financial [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	2,522,000	[1]
2015	2,566,000	[1]
2016	1,634,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Sales [Member] | Financial [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	87,043,000	[1]
2015	58,210,000	[1]
2016	41,490,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Physical [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	725,000	[1]
2015	559,000	[1]
2016	397,000	[1]
2017	397,000	[1]
2018	397,000	[1]
Thereafter	235,000	[1]
Purchase [Member] | Physical [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	18,282,000	[1]
2015	4,973,000	[1]
2016	2,505,000	[1]
2017	675,000	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Financial [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	1,768,000	[1]
2015	1,461,000	[1]
2016	948,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Financial [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	110,762,000	[1]
2015	82,825,000	[1]
2016	51,950,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
[1]	Physical transactions represent commodity transactions where Avista Utilities will take delivery of either electricity or natural gas and financial transactions represent derivative instruments with no physical delivery, such as futures, swaps or options.

Derivatives_And_Risk_Managemen4

Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) (Interest Rate Swap Agreements [Member], USD $)	3 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
	Caontracts	Caontracts
2014 [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Number of contracts	2	2
Derivative, Notional Amount	$50,000	$50,000
Derivative, Maturity Date	31-Dec-14	31-Dec-14
2015 [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Number of contracts	3	2
Derivative, Notional Amount	60,000	45,000
Derivative, Maturity Date	31-Dec-15	31-Dec-15
2016 [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Number of contracts	3	2
Derivative, Notional Amount	60,000	40,000
Derivative, Maturity Date	31-Dec-16	31-Dec-16
2017 [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Number of contracts	2	1
Derivative, Notional Amount	30,000	15,000
Derivative, Maturity Date	31-Dec-17	31-Dec-17
2018 [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Number of contracts	5	4
Derivative, Notional Amount	$115,000	$95,000
Derivative, Maturity Date	31-Dec-18	31-Dec-18

Derivatives_And_Risk_Managemen5

Derivatives And Risk Management (Derivative Instruments Summary) (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	$112,787,000		$89,132,000
Gross Liability	-101,890,000		-89,675,000
Collateral Netting	-502,000		8,732,000
Net Asset (Liability) in Balance Sheet	10,395,000		8,189,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	10,395,000		8,189,000
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	47,000		7,000
Gross Liability	-30,000		-6,000
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	17,000		1,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	17,000		1,000
Other Current Liabilities [Member] | Interest Rate Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	10,619,000		13,968,000
Gross Liability	0		0
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	10,619,000		13,968,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	10,619,000		13,968,000
Other Property and Investments-Net [Member] | Interest Rate Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	10,641,000		19,575,000
Gross Liability	-3,097,000		0
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	7,544,000		19,575,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	7,544,000		19,575,000
Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	58,483,000	[1]	7,416,000	[1]
Gross Liability	-41,846,000	[1]	-4,394,000	[1]
Collateral Netting	-2,712,000	[1]	0	[1]
Net Asset (Liability) in Balance Sheet	13,925,000	[1]	3,022,000	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	-158,000	[1]	0	[1]
Net Asset (Liability)	13,767,000	[1]	3,022,000	[1]
Non-Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	31,510,000	[1]	7,610,000	[1]
Gross Liability	-27,965,000	[1]	-6,756,000	[1]
Collateral Netting	0	[1]	0	[1]
Net Asset (Liability) in Balance Sheet	3,545,000	[1]	854,000	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	0	[1]	0	[1]
Net Asset (Liability)	3,545,000	[1]	854,000	[1]
Current Utility Energy Commodity Derivative Liabilities [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	1,415,000	[1]	23,455,000	[1]
Gross Liability	-4,775,000	[1]	-37,306,000	[1]
Collateral Netting	0	[1]	2,976,000	[1]
Net Asset (Liability) in Balance Sheet	-3,360,000	[1]	-10,875,000	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	158,000	[1]	0	[1]
Net Asset (Liability)	-3,202,000	[1]	-10,875,000	[1]
Other Noncurrent Liabilities [Member] | Interest Rate Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	0		'
Gross Liability	-8,906,000		'
Collateral Netting	2,210,000		'
Net Asset (Liability) in Balance Sheet	-6,696,000		'
Gross Assets Not Offset	0		'
Gross Liabilities Not Offset	0		'
Net Asset (Liability)	-6,696,000		'
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	72,000	[1]	17,101,000	[1]
Gross Liability	-15,271,000	[1]	-41,213,000	[1]
Collateral Netting	0	[1]	5,756,000	[1]
Net Asset (Liability) in Balance Sheet	-15,199,000	[1]	-18,356,000	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	0	[1]	0	[1]
Net Asset (Liability)	($15,199,000)	[1]	($18,356,000)	[1]
[1]	Avista Corp. has a master netting agreement that governs the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allows for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performs cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. does not perform cross-affiliate netting because the Company believes that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 are not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there is no additional netting which requires disclosure for that period.

Derivatives_And_Risk_Managemen6

Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2013
			Foreign Exchange Contract [Member]	Foreign Exchange Contract [Member]	Foreign Exchange Contract [Member]	Foreign Exchange Contract [Member]
			United States of America, Dollars	United States of America, Dollars	Canada, Dollars	Canada, Dollars
			USD ($)	USD ($)	CAD	CAD
Schedule of Foreign Currency Derivative Contracts Outstanding [Line Items]	'	'	'	'	'	'
Number Of Days Canadian Currency Prices Are Settled With U.S. Dollars	'60 days	'	'	'	'	'
Number of Foreign Currency Derivatives Held	23	23	'	'	'	'
Derivative, Notional Amount	'	'	$13,128	$8,631	14,596	9,191

Pension_Plans_And_Other_Postre2

Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Contributions to defined benefit pension plan	($11,000,000)	($14,670,000)	($44,300,000)
Pension Plans, Defined Benefit [Member]	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year	($32,000,000)	'	'

Pension_Plans_And_Other_Postre3

Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Service cost	$5,018	$4,743
Interest cost	6,706	5,978
Expected return on plan assets	-8,110	-6,900
Amortization of prior service cost	6	75
Net loss recognition	1,157	3,547
Net periodic benefit cost	4,777	7,443
Other Post-Retirement Benefits [Member]	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Service cost	974	1,032
Interest cost	1,353	1,390
Expected return on plan assets	-472	-400
Amortization of prior service cost	-43	-37
Net loss recognition	826	1,521
Net periodic benefit cost	$2,638	$3,506

Committed_Lines_of_Credit_Deta

Committed Lines of Credit (Details) (USD $)	3 Months Ended						3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2013	Feb. 28, 2011	Jul. 31, 2012	Mar. 31, 2014	Mar. 31, 2014
	Avista Corporation [Member]	Avista Corporation [Member]	Ecova [Member]	Ecova [Member]	Line of Credit [Member]	Line of Credit [Member]	Funded Debt to Ebitda Ratio [Member]	Fixed Charges Coverage Ratio [Member]
					Avista Corporation [Member]	Ecova [Member]	Ecova [Member]	Ecova [Member]
Short-term Debt [Line Items]	'	'	'	'	'	'	'	'
Line of Credit Facility, Maximum Borrowing Capacity	'	'	'	'	$400,000,000	$125,000,000	'	'
Line of Credit Facility, Covenant Terms	'0.65	'	'	'	'	'	'2.50	'1.50
Balance outstanding at end of period	111,000,000	171,000,000	42,000,000	46,000,000	'	'	'	'
Letters of credit outstanding at end of period	$9,614,000	$27,434,000	'	'	'	'	'	'
Average interest rate at end of period	0.93%	1.02%	2.16%	2.17%	'	'	'	'

LongTerm_Debt_Narrative_Detail

Long-Term Debt (Narrative) (Details) (USD $)	0 Months Ended
	Dec. 31, 1998	Mar. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]	'	'		'
Long-term Pollution Control Bond, Noncurrent	'	($83,700,000)	[1]	($83,700,000)	[1]
Debt instrument, interest rate, stated percentage	8.45%	'		'
Amount borrowed to acquire a long-term fixed rate electric capacity contract	145,000,000	'		'
Funds held in trust account which are used to secure long-term debt	'	1,600,000		'
2032 [Member] | Secured Debt [Member]	'	'		'
Debt Instrument [Line Items]	'	'		'
Long-term Pollution Control Bond, Noncurrent	'	66,700,000	[1]	66,700,000	[1]
2034 [Member] | Secured Debt [Member]	'	'		'
Debt Instrument [Line Items]	'	'		'
Long-term Pollution Control Bond, Noncurrent	'	$17,000,000	[1]	$17,000,000	[1]
2047 [Member] | First Mortgage Bonds [Member]	'	'		'
Debt Instrument [Line Items]	'	'		'
Debt instrument, interest rate, stated percentage	'	4.23%		'
[1]	In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.

LongTerm_Debt_Schedule_Of_Long

Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 1998

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

In Thousands, unless otherwise specified

2018, 5.95% [Member]

2018, 5.95% [Member]

2018, 7.39% - 7.45% [Member]

2018, 7.39% - 7.45% [Member]

2019 [Member]

2019 [Member]

2020 [Member]

2020 [Member]

2022 [Member]

2022 [Member]

2023, 7.18% - 7.54% [Member]

2023, 7.18% - 7.54% [Member]

2028 [Member]

2028 [Member]

2032 [Member]

2032 [Member]

2034 [Member]

2034 [Member]

2035 [Member]

2035 [Member]

2037 [Member]

2037 [Member]

2040 [Member]

2040 [Member]

2041 [Member]

2041 [Member]

2047 [Member]

2047 [Member]

2016 [Member]

2016 [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

Secured Debt [Member]

Secured Debt [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maturity Year

'

'

'

'2018

'

'2018

'

'2019

'

'2020

'

'2022

'

'2023

'

'2028

'

'2032

[1]

'

'2034

[1]

'

'2035

'

'2037

'

'2040

'

'2041

'

'2047

'

'2016

'

Debt instrument, interest rate, stated percentage

'

'

8.45%

5.95%

'

'

'

5.45%

'

3.89%

'

5.13%

'

'

'

6.37%

'

'

'

'

'

6.25%

'

5.70%

'

5.55%

'

4.45%

'

4.23%

'

0.84%

'

Interest Rate, minimum

'

'

'

'

'

7.39%

'

'

'

'

'

'

'

7.18%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Rate, maximum

'

'

'

'

'

7.45%

'

'

'

'

'

'

'

7.54%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Medium-Term Notes, Noncurrent

'

'

'

'

'

$22,500

$22,500

'

'

'

'

'

'

$13,500

$13,500

$25,000

$25,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Secured long-term debt

1,376,700

1,376,700

'

250,000

250,000

'

'

90,000

90,000

52,000

52,000

250,000

250,000

'

'

'

'

'

'

'

'

150,000

150,000

150,000

150,000

35,000

35,000

85,000

85,000

80,000

80,000

90,000

90,000

Other long-term debt and capital leases

1,272,530

1,272,425

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Settled interest rate swaps

-23,413

[2]

-23,560

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unamortized debt discount

-1,246

-1,287

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total

1,356,602

1,356,483

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pollution Control Bonds

-83,700

[1]

-83,700

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

66,700

[1]

66,700

[1]

17,000

[1]

17,000

[1]

'

'

'

'

'

'

'

'

'

'

'

'

Other Long-term Debt and Capital Lease Obligations

4,561

4,630

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long-term Debt and Capital Lease Obligations, Current

($372)

($358)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.

[2]

Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.

Fair_Value_Carrying_Value_And_

Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Reported Value Measurement [Member] | Level 2 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	$951,000	$951,000
Reported Value Measurement [Member] | Level 3 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	342,000	342,000
Reported Value Measurement [Member] | Level 3 [Member] | Affiliated Entity [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	51,547	51,547
Reported Value Measurement [Member] | Level 3 [Member] | Nonrecourse Long-Term Debt [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	13,872	17,838
Estimate of Fair Value Measurement [Member] | Level 2 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	1,080,124	1,054,512
Estimate of Fair Value Measurement [Member] | Level 3 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	345,980	329,581
Estimate of Fair Value Measurement [Member] | Level 3 [Member] | Affiliated Entity [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	37,052	37,114
Estimate of Fair Value Measurement [Member] | Level 3 [Member] | Nonrecourse Long-Term Debt [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	$14,323	$18,636

Fair_Value_Fair_Value_Of_Asset

Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	$112,787		$89,132		'	'
Securities available for sale:	59,199		69,361		'	'
Liability	101,890		89,675		'	'
Cash and cash equivalents	90,172		82,574		89,197	75,464
Fixed Income Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Cash and cash equivalents	900		700		'	'
Fair Value, Measurements, Recurring [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Foreign currency derivatives	17		1		'	'
Interest rate swaps	18,163		33,543		'	'
Money Market Funds, Fair Value	23,034		11,180		'	'
Funds held in trust account of Spokane Energy	1,600		1,600		'	'
Total	127,864		127,991		'	'
Foreign currency derivative liabilities at fair value	0		0		'	'
Interest rate swaps	6,696		'		'	'
Total	25,255		29,231		'	'
Fair Value, Measurements, Recurring [Member] | Energy commodity derivatives [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	17,470		3,876		'	'
Liability	2,089		12,796		'	'
Fair Value, Measurements, Recurring [Member] | Power Option Agreement [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	428		775		'	'
Fair Value, Measurements, Recurring [Member] | Natural Gas Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	2,418		1,219		'	'
Fair Value, Measurements, Recurring [Member] | Power Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	0		0		'	'
Liability	13,624		14,441		'	'
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	54,327		61,078		'	'
Fair Value, Measurements, Recurring [Member] | Municipal [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	3,109		3,518		'	'
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		3,000		'	'
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	763		765		'	'
Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	1,000		1,000		'	'
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	1,906	[1]	1,960	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	6,475	[1]	6,470	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Money Market Funds, Fair Value	23,034		11,180		'	'
Funds held in trust account of Spokane Energy	1,600		1,600		'	'
Total	33,015		21,210		'	'
Total	0		0		'	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed Income Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	1,906	[1]	1,960	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	6,475	[1]	6,470	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Foreign currency derivatives	47		7		'	'
Interest rate swaps	21,260		33,543		'	'
Total	171,596		158,154		'	'
Foreign currency derivative liabilities at fair value	30		6		'	'
Interest rate swaps	12,003		'		'	'
Total	85,030		72,901		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Energy commodity derivatives [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	91,090		55,243		'	'
Liability	72,997		72,895		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government Agency [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	54,327		61,078		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	3,109		3,518		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate fixed income - financial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		3,000		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate fixed income - industrial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	763		765		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Certificates of deposits [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	1,000		1,000		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Total	390		339		'	'
Total	16,860		16,774		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Option Agreement [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	428		775		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Natural Gas Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	2,418		1,219		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	390		339		'	'
Liability	14,014		14,780		'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Foreign currency derivatives	-30	[2]	-6	[2]	'	'
Interest rate swaps	-3,097		'		'	'
Total	-77,137	[2]	-51,712	[2]	'	'
Foreign currency derivative liabilities at fair value	-30		-6		'	'
Interest rate swaps	-5,307		'		'	'
Total	-76,635	[2]	-60,444	[2]	'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Energy commodity derivatives [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	-73,620	[2]	-51,367	[2]	'	'
Liability	-70,908	[2]	-60,099	[2]	'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Natural Gas Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	'		0	[2]	'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Power Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	-390		-339	[2]	'	'
Liability	($390)		($339)	[2]	'	'
[1]	These assets are trading securities and are included in other property and investments-net on the Condensed Consolidated Balance Sheets.
[2]	The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties.

Fair_Value_Quantitative_Inform

Fair Value (Quantitative Information) (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

In Thousands, unless otherwise specified

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Average [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

IDAHO

WASHINGTON

Sales [Member]

Sales [Member]

Purchase [Member]

Purchase [Member]

2014 to 2019 [Member]

Black Scholes Merton [Member]

2014 [Member]

2015 [Member]

2016 [Member]

2017 [Member]

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Exchange Agreements [Member]

Power Exchange Agreements [Member]

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Surrogate Facility Pricing [Member]

Black Scholes Merton [Member]

Black Scholes Merton [Member]

Black Scholes Merton [Member]

Black Scholes Merton [Member]

Surrogate Facility Pricing [Member]

Black Scholes Merton [Member]

Surrogate Facility Pricing [Member]

Black Scholes Merton [Member]

Surrogate Facility Pricing [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

MWh

MWh

MWh

MWh

Internally Derived Weighted Average Cost Of Gas [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

MMBTU

MMBTU

MMBTU

MMBTU

Fair Value Inputs, Assets, Quantitative Information [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gross Liability

($101,890)

($89,675)

'

'

'

'

'

'

'

'

'

'

'

($13,624)

($14,441)

($428)

($775)

($2,418)

($1,219)

'

'

'

'

'

'

Operation and Maintenance Charges

'

'

'

'

'

'

'

'

30.18

[1]

'

53.9

[1]

'

40.93

[1]

'

'

'

'

'

'

40.93

42.44

'

'

'

'

Escalation Factor

'

'

3.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Price Risk Option Strike Price

'

'

'

'

'

69.98

56.53

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Assumptions, Expected Volatility Rate

'

'

'

20.00%

[2]

31.00%

[2]

'

'

18.00%

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Forward Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.54

5.23

3.66

4.45

Transaction/Delivery Volumes

'

'

'

'

'

'

'

'

396,984

128,278

397,116

286,307

'

'

'

'

'

'

'

'

'

279,990

310,000

280,000

310,000

[1]

The average O&M charges for the delivery year beginning in November 2013 were $40.93 per MWh. For ratemaking purposes the average O&M calculations vary slightly between regulatory jurisdictions. The average O&M charges for the delivery year beginning in 2013 were $42.44 for Washington and $40.93 for Idaho.

[2]

The estimated volatility rate of 0.20 is compared to actual quoted volatility rates of 0.31 for 2014 to 0.18 in April 2017.

Fair_Value_Reconciliation_For_

Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) (Fair Value, Inputs, Level 3 [Member], USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Balance	($16,435)		($22,551)
Included in net income	0		0
Included in other comprehensive income	0		0
Included in regulatory assets/liabilities	4,222	[1]	1,054	[1]
Purchases	0		0
Issuances	0		0
Settlements	-4,257		1,843
Transfers from other categories	0		0
Ending Balance	-16,470		-19,654
Natural Gas Exchange Agreements [Member]	'		'
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Balance	-1,219		-2,379
Included in net income	0		0
Included in other comprehensive income	0		0
Included in regulatory assets/liabilities	1,849	[1]	750	[1]
Purchases	0		0
Issuances	0		0
Settlements	-3,048		-362
Transfers from other categories	0		0
Ending Balance	-2,418		-1,991
Power Exchange Agreements [Member]	'		'
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Balance	-14,441		-18,692
Included in net income	0		0
Included in other comprehensive income	0		0
Included in regulatory assets/liabilities	2,026	[1]	24	[1]
Purchases	0		0
Issuances	0		0
Settlements	-1,209		2,205
Transfers from other categories	0		0
Ending Balance	-13,624		-16,463
Power Option Agreement [Member]	'		'
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'
Beginning Balance	-775		-1,480
Included in net income	0		0
Included in other comprehensive income	0		0
Included in regulatory assets/liabilities	347	[1]	280	[1]
Purchases	0		0
Issuances	0		0
Settlements	0		0
Transfers from other categories	0		0
Ending Balance	($428)		($1,200)
[1]	(1)The UTC and the IPUC issued accounting orders authorizing Avista Corp. to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Corp. to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates cases.

Earnings_Per_Share_Attributabl

Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Numerator:	'	'
Net income attributable to Avista Corporation shareholders	$48,499	$42,341
Subsidiary earnings adjustment for dilutive securities	-53	-43
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$48,446	$42,298
Denominator:	'	'
Weighted-average number of common shares outstanding-basic	60,122	59,866
Performance and restricted stock awards	46	32
Weighted-average number of common shares outstanding-diluted	60,168	59,898
Earnings per common share attributable to Avista Corporation:	'	'
Basic	$0.81	$0.71
Diluted (usd per share)	$0.81	$0.71

Commitments_And_Contingencies_

Commitments And Contingencies (Details) (USD $)	1 Months Ended	3 Months Ended
	31-May-04	Mar. 31, 2014
		hydroelectric_plant
		gal
		employee
Number Of Bargaining Unit Employees Oregon	'	50
Amount of Regulatory Costs Not yet Approved	'	$1,300,000
Gallons of Diesel Spilled	'	10,000
Percentage Of Employees, Collective Bargaining Agreement	'	45.00%
Majority Of Bargaining Unit Employees, Percentage	'	90.00%
Investigation review bid maximum (per MW)	250	'
Customer refund liability	'	200,000
Litigation Settlement, Amount	'	15,000,000
Number of hydroelectric plants	'	6
Number of years, license issued	'	'50 years
WASHINGTON	'	'
Amount of Regulatory Costs Not yet Approved	'	900,000
IDAHO	'	'
Amount of Regulatory Costs Not yet Approved	'	$500,000

Information_By_Business_Segmen2

Information By Business Segments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]	'		'		'
Operating revenues	$490,962		$482,906		'
Resource costs	220,497		229,630		'
Other operating expenses	114,597		110,779		'
Depreciation and amortization	34,582		31,618		'
Income from operations	93,140		85,062		'
Interest expense	19,195	[1]	19,810	[1]	'
Income taxes	28,176		25,236		'
Net income (loss) attributable to Avista Corporation	48,499		42,341		'
Payments to Acquire Other Property, Plant, and Equipment	63,654		71,464		'
Total assets	4,316,078		'		4,361,923
Avista Utilities [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating revenues	437,574		431,577		'
Resource costs	220,497		229,630		'
Other operating expenses	67,337		65,444		'
Depreciation and amortization	30,726		27,935		'
Income from operations	90,868		82,751		'
Interest expense	18,546	[1]	18,770	[1]	'
Income taxes	27,620		24,780		'
Net income (loss) attributable to Avista Corporation	47,996		42,250		'
Payments to Acquire Other Property, Plant, and Equipment	59,725		70,645		'
Total assets	3,893,474		'		3,940,998
Ecova [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating revenues	44,384		42,407		'
Resource costs	0		0		'
Other operating expenses	37,877		35,990		'
Depreciation and amortization	3,709		3,493		'
Income from operations	2,798		2,924		'
Interest expense	340	[1]	444	[1]	'
Income taxes	894		984		'
Net income (loss) attributable to Avista Corporation	1,111		1,198		'
Payments to Acquire Other Property, Plant, and Equipment	3,883		794		'
Total assets	344,828		'		339,643
Other Business Segment [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating revenues	9,454		9,372		'
Resource costs	0		0		'
Other operating expenses	9,833		9,795		'
Depreciation and amortization	147		190		'
Income from operations	-526		-613		'
Interest expense	397	[1]	673	[1]	'
Income taxes	-338		-528		'
Net income (loss) attributable to Avista Corporation	-608		-1,107		'
Payments to Acquire Other Property, Plant, and Equipment	46		25		'
Total assets	77,776		'		81,282
Total Non-Utility [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating revenues	53,838		51,779		'
Resource costs	0		0		'
Other operating expenses	47,710		45,785		'
Depreciation and amortization	3,856		3,683		'
Income from operations	2,272		2,311		'
Interest expense	737	[1]	1,117	[1]	'
Income taxes	556		456		'
Net income (loss) attributable to Avista Corporation	503		91		'
Payments to Acquire Other Property, Plant, and Equipment	3,929		819		'
Total assets	422,604		'		420,925
Intersegment Eliminations [Member]	'		'		'
Segment Reporting Information [Line Items]	'		'		'
Operating revenues	-450	[2]	-450	[2]	'
Resource costs	0	[2]	0	[2]	'
Other operating expenses	-450	[2]	-450	[2]	'
Depreciation and amortization	0	[2]	0	[2]	'
Income from operations	0	[2]	0	[2]	'
Interest expense	-88	[1],[2]	-77	[1],[2]	'
Income taxes	0	[2]	0	[2]	'
Net income (loss) attributable to Avista Corporation	0	[2]	0	[2]	'
Payments to Acquire Other Property, Plant, and Equipment	0	[2]	0	[2]	'
Total assets	$0	[2]	'		$0	[2]
[1]	Including interest expense to affiliated trusts.
[2]	Intersegment eliminations reported as operating revenues and resource costs represent intercompany purchases and sales of electric capacity and energy. Intersegment eliminations reported as interest expense represent intercompany interest.