Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	12 Months Ended
	Dec. 31, 2014 frequency
Sales [Member] | Electric Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	326,000	[1]
2016	287,000	[1]
2017	286,000	[1]
2018	286,000	[1]
2019	158,000	[1]
Thereafter	0	[1]
Sales [Member] | Electric Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	2,951,000	[1]
2016	1,634,000	[1]
2017	290,000	[1]
2018	0	[1]
2019	0	[1]
Thereafter	0	[1]
Sales [Member] | Gas Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	3,428,000	[1]
2016	910,000	[1]
2017	0	[1]
2018	0	[1]
2019	0	[1]
Thereafter	0	[1]
Sales [Member] | Gas Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	99,023,000	[1]
2016	56,520,000	[1]
2017	15,420,000	[1]
2018	0	[1]
2019	0	[1]
Thereafter	0	[1]
Purchase [Member] | Electric Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	522,000	[1]
2016	397,000	[1]
2017	397,000	[1]
2018	397,000	[1]
2019	235,000	[1]
Thereafter	0	[1]
Purchase [Member] | Electric Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	2,547,000	[1]
2016	1,071,000	[1]
2017	0	[1]
2018	0	[1]
2019	0	[1]
Thereafter	0	[1]
Purchase [Member] | Gas Derivative [Member] | Physical [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	21,111,000	[1]
2016	2,505,000	[1]
2017	675,000	[1]
2018	0	[1]
2019	0	[1]
Thereafter	0	[1]
Purchase [Member] | Gas Derivative [Member] | Financial [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
2015	120,780,000	[1]
2016	70,480,000	[1]
2017	24,230,000	[1]
2018	3,020,000	[1]
2019	1,800,000	[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.