Derivatives And Risk Management (Energy Commodity Derivatives) (Details) frequency in Thousands, Volt in Thousands	9 Months Ended
	Sep. 30, 2015 Volt frequency	[1]
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015	39
2016	256
2017	286
2018	286
2019	158
Thereafter	0
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015 | Volt	1,683
2016 | Volt	1,370
2017 | Volt	1,360
2018	1,360
2019	1,345
Thereafter | Volt	2,470
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015	1,142
2016	2,365
2017	483
2018	0
2019	0
Thereafter	0
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015 | Volt	32,768
2016 | Volt	91,398
2017 | Volt	19,008
2018 | Volt	2,738
2019	0
Thereafter | Volt	0
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015	171
2016	394
2017	397
2018	397
2019	235
Thereafter	0
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015 | Volt	8,962
2016 | Volt	10,600
2017 | Volt	675
2018 | Volt	0
2019 | Volt	0
Thereafter | Volt	0
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015	805
2016	1,642
2017	0
2018	0
2019	0
Thereafter	0
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2015 | Volt	50,538
2016 | Volt	118,228
2017 | Volt	35,823
2018 | Volt	10,288
2019 | Volt	4,500
Thereafter | Volt	0

[1] Physical transactions represent commodity transactions in which Avista Utilities will take or make delivery of either electricity or natural gas; financial transactions represent derivative instruments with delivery of cash in the amount of gain or loss but with no physical delivery of the commodity, such as futures, swaps, options, or forward contracts.