Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Jun. 29, 2014
Summary Of Significant Accounting Policies [Line Items]
Maximum Dividends Allowed by Debt Covenants	$ 397,400
Sale and maturity of securities available for sale	0	$ 14,612
Maximum Dividends Allowed by Regulator Approval	$ 252,200
Ecova [Member]
Summary Of Significant Accounting Policies [Line Items]
Owners percentage interest			80.20%
Avista Utilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Regulatory Restrictions, Maximum Debt to Equity	40.00%
Avista Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Line of Credit Facility, Covenant Terms, Maximum Debt to Equity Ratio	65.00%