Revenue Revenue Utility Related Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Public Utility Operating Expenses Excise Taxes Collected	$ 19,089	$ 19,167

Public Utility Operating Expenses Excise Taxes Collected and Reported Gross in Revenues and Operating Expenses

No definition available.

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