Committed Lines of Credit (Details) (USD $)	3 Months Ended						3 Months Ended
	Mar. 31, 2014 Avista Corporation [Member]	Dec. 31, 2013 Avista Corporation [Member]	Mar. 31, 2014 Ecova [Member]	Dec. 31, 2013 Ecova [Member]	Feb. 28, 2011 Line of Credit [Member] Avista Corporation [Member]	Jul. 31, 2012 Line of Credit [Member] Ecova [Member]	Mar. 31, 2014 Funded Debt to Ebitda Ratio [Member] Ecova [Member]	Mar. 31, 2014 Fixed Charges Coverage Ratio [Member] Ecova [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 400,000,000	$ 125,000,000
Line of Credit Facility, Covenant Terms	0.65						2.50	1.50
Balance outstanding at end of period	111,000,000	171,000,000	42,000,000	46,000,000
Letters of credit outstanding at end of period	$ 9,614,000	$ 27,434,000
Average interest rate at end of period	0.93%	1.02%	2.16%	2.17%