Committed Lines of Credit (Details) (USD $)	6 Months Ended
	Jun. 30, 2014 Avista Corporation [Member]	Dec. 31, 2013 Avista Corporation [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]
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
Balance outstanding at end of period	151,500,000	171,000,000	46,000,000
Letters of credit outstanding at end of period	$ 21,864,000	$ 27,434,000
Average interest rate at end of period	3.02%	1.02%	2.17%