Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jun. 29, 2014
Summary Of Significant Accounting Policies [Line Items]
Maximum Dividends Allowed by Debt Covenants	$ 414,300,000
Sale and maturity of securities available for sale	0	11,403,000
Maximum Dividends Allowed by Regulator Approval	$ 278,400,000
Ecova [Member]
Summary Of Significant Accounting Policies [Line Items]
Owners percentage interest			80.20%
Avista Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Line of Credit Facility, Covenant Terms	0.65