Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	6 Months Ended
	Jun. 30, 2013 Volt
Purchases [Member] | Physical [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	13,910,000
2014	6,808,000
2015	3,768,000
2016	1,745,000
2017	225,000
Thereafter	0
Purchases [Member] | Physical [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	555,000	[1]
2014	620,000	[1]
2015	379,000	[1]
2016	367,000	[1]
2017	366,000	[1]
Thereafter	583,000	[1]
Purchases [Member] | Financial [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	61,099,000
2014	84,332,000
2015	55,920,000
2016	23,960,000
2017	0
Thereafter	0
Purchases [Member] | Financial [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	1,923,000	[1]
2014	1,323,000	[1]
2015	982,000	[1]
2016	0	[1]
2017	0	[1]
Thereafter	0	[1]
Sales [Member] | Physical [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	1,973,000
2014	1,786,000
2015	0
2016	0
2017	0
Thereafter	0
Sales [Member] | Physical [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	270,000
2014	377,000
2015	254,000
2016	287,000
2017	286,000
Thereafter	443,000
Sales [Member] | Financial [Member] | Gas Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	45,646,000
2014	53,263,000
2015	46,840,000
2016	13,380,000
2017	0
Thereafter	0
Sales [Member] | Financial [Member] | Electric Derivatives [Member]
Energy Commodity Derivative Volumes [Line Items]
2013	2,164,000
2014	2,599,000
2015	1,463,000
2016	675,000
2017	0
Thereafter	0

[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.