Summary Of Significant Accounting Policies (Asset Retirement Obligations) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligations [Abstract]
Regulatory liability for utility plant retirement costs	$ 261,594	$ 254,140

Utility plant retirement costs recovered through rates charged to customers as a portion of depreciation expense. These costs do not represent legal or contractual obligations.

No definition available.

Name:	ava_RegulatoryLiabilityForUtilityPlantRetirementCostsNoncurrent
Namespace Prefix:	ava_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant