Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Secured Debt	$ 1,696,700,000	$ 1,611,700,000
Asset	61,191,000	76,865,000
Liability	(150,381,000)	(210,512,000)
Collateral Netting	44,758,000	48,556,000
Net Asset (Liability)	(44,432,000)	(85,091,000)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netting	34,900,000	34,030,000
Collateral Already Posted, Aggregate Fair Value	34,900,000	34,030,000
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Collateral Netting	9,858,000	14,526,000
Collateral Already Posted, Aggregate Fair Value	17,134,000	28,716,000
Other Current Liabilities [Member] | Foreign Currency Exchange Contracts [Member]
Derivatives, Fair Value [Line Items]
Asset	5,000	2,000
Liability	(28,000)	(19,000)
Collateral Netting	0	0
Net Asset (Liability)	(23,000)	(17,000)
Other Current Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Asset	0	118,000
Liability	(15,756,000)	(23,262,000)
Collateral Netting	9,731,000	3,880,000
Net Asset (Liability)	(6,025,000)	(19,264,000)
Non-Current Interest Rate Swap Derivative Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Asset	3,951,000	1,407,000
Liability	(57,825,000)	(62,236,000)
Collateral Netting	25,169,000	30,150,000
Net Asset (Liability)	(28,705,000)	(30,679,000)
Other Current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Asset	3,393,000
Liability	0
Collateral Netting	0
Net Asset (Liability)	3,393,000
Other Current Assets [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Asset	18,682,000	1,236,000
Liability	(16,787,000)	(553,000)
Collateral Netting	0	0
Net Asset (Liability)	1,895,000	683,000
Other Property And Investments Net And Other Non-current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Asset	5,754,000	23,000
Liability	(397,000)	0
Collateral Netting	0	0
Net Asset (Liability)	5,357,000	23,000
Current Utility Energy Commodity Derivative Liabilities [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Asset	16,335,000	67,466,000
Liability	(29,598,000)	(85,409,000)
Collateral Netting	6,228,000	3,675,000
Net Asset (Liability)	(7,035,000)	(14,268,000)
Other Noncurrent Liabilities [Member] | Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Asset	13,071,000	6,613,000
Liability	(29,990,000)	(39,033,000)
Collateral Netting	3,630,000	10,851,000
Net Asset (Liability)	(13,289,000)	(21,569,000)
Avista Utilities [Member]
Derivatives, Fair Value [Line Items]
Secured Debt	1,621,700,000	1,536,700,000
First Mortgage [Member] | Avista Utilities [Member] | 2051
Derivatives, Fair Value [Line Items]
Secured Debt	$ 175,000,000	$ 0