Derivatives And Risk Management (Derivative Instruments Summary) (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Gross Asset	$ 112,787,000		$ 89,132,000
Gross Liability	(101,890,000)		(89,675,000)
Collateral Netting	(502,000)		8,732,000
Net Asset (Liability) in Balance Sheet	10,395,000		8,189,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	10,395,000		8,189,000
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	47,000		7,000
Gross Liability	(30,000)		(6,000)
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	17,000		1,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	17,000		1,000
Other Current Liabilities [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	10,619,000		13,968,000
Gross Liability	0		0
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	10,619,000		13,968,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	10,619,000		13,968,000
Other Property and Investments-Net [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	10,641,000		19,575,000
Gross Liability	(3,097,000)		0
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	7,544,000		19,575,000
Gross Assets Not Offset	0		0
Gross Liabilities Not Offset	0		0
Net Asset (Liability)	7,544,000		19,575,000
Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	58,483,000	[1]	7,416,000	[1]
Gross Liability	(41,846,000)	[1]	(4,394,000)	[1]
Collateral Netting	(2,712,000)	[1]	0	[1]
Net Asset (Liability) in Balance Sheet	13,925,000	[1]	3,022,000	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	(158,000)	[1]	0	[1]
Net Asset (Liability)	13,767,000	[1]	3,022,000	[1]
Non-Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	31,510,000	[1]	7,610,000	[1]
Gross Liability	(27,965,000)	[1]	(6,756,000)	[1]
Collateral Netting	0	[1]	0	[1]
Net Asset (Liability) in Balance Sheet	3,545,000	[1]	854,000	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	0	[1]	0	[1]
Net Asset (Liability)	3,545,000	[1]	854,000	[1]
Current Utility Energy Commodity Derivative Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	1,415,000	[1]	23,455,000	[1]
Gross Liability	(4,775,000)	[1]	(37,306,000)	[1]
Collateral Netting	0	[1]	2,976,000	[1]
Net Asset (Liability) in Balance Sheet	(3,360,000)	[1]	(10,875,000)	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	158,000	[1]	0	[1]
Net Asset (Liability)	(3,202,000)	[1]	(10,875,000)	[1]
Other Noncurrent Liabilities [Member] | Interest Rate Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0
Gross Liability	(8,906,000)
Collateral Netting	2,210,000
Net Asset (Liability) in Balance Sheet	(6,696,000)
Gross Assets Not Offset	0
Gross Liabilities Not Offset	0
Net Asset (Liability)	(6,696,000)
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	72,000	[1]	17,101,000	[1]
Gross Liability	(15,271,000)	[1]	(41,213,000)	[1]
Collateral Netting	0	[1]	5,756,000	[1]
Net Asset (Liability) in Balance Sheet	(15,199,000)	[1]	(18,356,000)	[1]
Gross Assets Not Offset	0	[1]	0	[1]
Gross Liabilities Not Offset	0	[1]	0	[1]
Net Asset (Liability)	$ (15,199,000)	[1]	$ (18,356,000)	[1]

[1] Avista Corp. has a master netting agreement that governs the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allows for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performs cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. does not perform cross-affiliate netting because the Company believes that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 are not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there is no additional netting which requires disclosure for that period.