Energy Purchase Contracts (Schedule Of Utility Total Expenses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Energy Purchase Contracts [Abstract]
Utility power resources	$ 557,619	$ 649,408	$ 704,886

The total amount of power purchased, natural gas purchased, fuel for generation and other fuel costs, which are included in utility resource costs in the Consolidated Statements of Income

No definition available.

Name:	ava_UtilityPowerResources
Namespace Prefix:	ava_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration