Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) (USD $)	9 Months Ended			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	1 Months Ended	9 Months Ended	12 Months Ended	1 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 2014 [Member] Interest Rate Swap Agreements [Member] Caontracts	Dec. 31, 2013 2014 [Member] Interest Rate Swap Agreements [Member] Caontracts	Sep. 30, 2014 2015 [Member] Interest Rate Swap Agreements [Member] Caontracts	Dec. 31, 2013 2015 [Member] Interest Rate Swap Agreements [Member] Caontracts	Sep. 30, 2014 2016 [Member] Interest Rate Swap Agreements [Member] Caontracts	Dec. 31, 2013 2016 [Member] Interest Rate Swap Agreements [Member] Caontracts	Sep. 30, 2014 2017 [Member] Interest Rate Swap Agreements [Member] Caontracts	Dec. 31, 2013 2017 [Member] Interest Rate Swap Agreements [Member] Caontracts	Oct. 31, 2014 Two Thousand Eighteen [Member] Interest Rate Swap Agreements [Member]	Sep. 30, 2014 Two Thousand Eighteen [Member] Interest Rate Swap Agreements [Member] Caontracts	Dec. 31, 2013 Two Thousand Eighteen [Member] Interest Rate Swap Agreements [Member] Caontracts	Oct. 31, 2014 Subsequent Event [Member]	Oct. 31, 2014 Subsequent Event [Member] 2014 [Member] Interest Rate Swap Agreements [Member] Caontracts	Oct. 31, 2014 Subsequent Event [Member] Two Thousand Eighteen [Member] Interest Rate Swap Agreements [Member] Caontracts	Sep. 30, 2014 Avista Corporation [Member]	Dec. 31, 2013 Avista Corporation [Member]	Oct. 31, 2014 2044 [Member] First Mortgage Bonds [Member] Avista Corporation [Member] Subsequent Event [Member]
Derivatives, Fair Value [Line Items]
Number of contracts				2	2	5	2	5	2	3	1		7	4		2	9
Number of Interest Rate Derivatives Entered into Subsequent to Period End																	2
Derivative, Notional Amount				$ 50,000,000	$ 50,000,000	$ 75,000,000	$ 45,000,000	$ 95,000,000	$ 40,000,000	$ 45,000,000	$ 15,000,000		$ 155,000,000	$ 95,000,000			$ 205,000,000
Derivative, Maturity Date				Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2017	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2018
Payments for (Proceeds from) Derivative Instrument, Financing Activities	0	2,901,000													5,400,000
Secured Debt	1,451,700,000		1,376,700,000															1,376,700,000	1,376,700,000	60,000,000
Derivative Notional Amount Subsequent to Period End																	$ 50,000,000