Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	3 Months Ended
	Mar. 31, 2015 frequency
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	253,000	[1]
2015	287,000	[1]
2016	286,000	[1]
2017	286,000	[1]
2018	158,000	[1]
Thereafter	0	[1]
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	2,079,000	[1]
2015	910,000	[1]
2016	0	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	2,730,000	[1]
2015	1,826,000	[1]
2016	483,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	83,313,000	[1]
2015	63,000,000	[1]
2016	15,420,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	203,000	[1]
2015	397,000	[1]
2016	397,000	[1]
2017	397,000	[1]
2018	235,000	[1]
Thereafter	0	[1]
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	10,357,000	[1]
2015	2,505,000	[1]
2016	675,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	1,839,000	[1]
2015	1,287,000	[1]
2016	0	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2014	97,928,000	[1]
2015	81,730,000	[1]
2016	31,930,000	[1]
2017	6,795,000	[1]
2018	4,050,000	[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.