Committed Lines of Credit (Details) (USD $)	12 Months Ended								12 Months Ended
	Dec. 31, 2013 Avista Corporation [Member]	Dec. 31, 2012 Avista Corporation [Member]	Dec. 31, 2011 Avista Corporation [Member]	Dec. 31, 2013 Ecova [Member]	Dec. 31, 2012 Ecova [Member]	Dec. 31, 2011 Ecova [Member]	Feb. 28, 2011 Line of Credit [Member] Avista Corporation [Member]	Jul. 31, 2012 Line of Credit [Member] Ecova [Member]	Dec. 31, 2013 Funded Debt to Ebitda Ratio [Member] Ecova [Member]	Dec. 31, 2013 Fixed Charges Coverage Ratio [Member] Ecova [Member]
Short-term Debt [Line Items]
Total amount of committed line of credit agreement							$ 400,000,000	$ 125,000,000
Balance outstanding at end of period	171,000,000	52,000,000	61,000,000	46,000,000	54,000,000	35,000,000
Letters of credit outstanding at end of period	$ 27,434,000	$ 35,885,000	$ 29,030,000
Average interest rate at end of period	1.02%	1.12%	1.12%	2.17%	2.21%	2.38%
Ratio Required to Comply With Customary Covenants	65.00%								250.00%	150.00%