Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) Caontracts	Dec. 31, 2015 USD ($) Caontracts	Dec. 31, 2014 USD ($)
Derivatives, Fair Value [Line Items]
Secured Debt	$ 1,696,700	$ 1,611,700
Derivative, Fair Value, Amount Offset Against Collateral, Net	44,758	48,556
Payments For (Proceeds From) Derivative Instrument Operating Activities	53,966	0	$ 0
Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	$ 34,900	$ 34,030
2016 | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Swaps Settled | Caontracts	7
Number of contracts | Caontracts		6
Derivative, Notional Amount		$ 115,000
Derivative, Maturity Date		Dec. 31, 2016
Settled Derivative, Notional Amount	$ 125,000
2017 | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	6	3
Derivative, Notional Amount	$ 75,000	$ 45,000
Derivative, Maturity Date	Dec. 31, 2017	Dec. 31, 2017
2018 | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	14	11
Derivative, Notional Amount	$ 275,000	$ 245,000
Derivative, Maturity Date	Dec. 31, 2018	Dec. 31, 2018
2019 | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	6	2
Derivative, Notional Amount	$ 70,000	$ 30,000
Derivative, Maturity Date	Dec. 31, 2019	Dec. 31, 2019
2020 | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	2
Derivative, Notional Amount	$ 20,000
Derivative, Maturity Date	Dec. 31, 2020
2022 | Interest Rate Swap Agreements [Member]
Derivatives, Fair Value [Line Items]
Number of contracts | Caontracts	5	1
Derivative, Notional Amount	$ 60,000	$ 20,000
Derivative, Maturity Date	Dec. 31, 2022	Dec. 31, 2022
Avista Utilities [Member]
Derivatives, Fair Value [Line Items]
Secured Debt	$ 1,621,700	$ 1,536,700
Avista Utilities [Member] | 2051 | First Mortgage [Member]
Derivatives, Fair Value [Line Items]
Secured Debt	175,000	0
Avista Utilities [Member] | 2016 | First Mortgage [Member]
Derivatives, Fair Value [Line Items]
Secured Debt	$ 0	$ 90,000