Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details) (USD $) In Thousands, unless otherwise specified						6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended				6 Months Ended				6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2014		Dec. 31, 2013		Dec. 31, 1998	Jun. 30, 2014 2018, 5.95% [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2018, 5.95% [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2018, 7.39% - 7.45% [Member] Secured Debt [Member]	Dec. 31, 2013 2018, 7.39% - 7.45% [Member] Secured Debt [Member]	Jun. 30, 2014 2019 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2019 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2020 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2020 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2022 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2022 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2023, 7.18% - 7.54% [Member] Secured Debt [Member]	Dec. 31, 2013 2023, 7.18% - 7.54% [Member] Secured Debt [Member]	Jun. 30, 2014 2028 [Member] Secured Debt [Member]	Dec. 31, 2013 2028 [Member] Secured Debt [Member]	Jun. 30, 2014 2032 [Member] Secured Debt [Member]		Dec. 31, 2013 2032 [Member] Secured Debt [Member]		Jun. 30, 2014 2034 [Member] Secured Debt [Member]		Dec. 31, 2013 2034 [Member] Secured Debt [Member]		Jun. 30, 2014 2035 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2035 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2037 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2037 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2040 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2040 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2041 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2041 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2047 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2047 [Member] First Mortgage Bonds [Member]	Jun. 30, 2014 2016 [Member] First Mortgage Bonds [Member]	Dec. 31, 2013 2016 [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	1,268,530		1,272,425
Settled interest rate swaps	(23,265)	[2]	(23,560)	[2]
Unamortized debt discount	(1,205)		(1,287)
Total	1,356,578		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	4,348		4,630
Long-term Debt and Capital Lease Obligations, Current	$ (4,348)		$ (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.