Accounting For Income Taxes (Schedule Of Deferred Income Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Income Tax Disclosure [Abstract]
Allowance for doubtful accounts	$ 12,140		$ 12,086
Reserves not currently deductible	5,923		6,302
Net operating loss from subsidiary acquisition	11,136		14,867
Deferred compensation	3,631		3,248
Unfunded benefit obligation	94,891		80,939
Utility energy commodity derivatives	22,953		38,999
Power and natural gas deferrals	12,490		9,545
Tax credits	19,401		16,924
Other	19,291		18,838
Total deferred income tax assets	201,856		201,748
Intangible assets from subsidiary acquisition	5,582		8,334
Differences between book and tax basis of utility plant	494,579		478,604
Regulatory asset for pensions and other postretirement benefits	107,243		91,125
Power exchange contract	10,753		15,571
Utility energy commodity derivatives	22,954		38,992
Loss on reacquired debt	6,751		7,193
Interest rate swaps	12,308		3,720
Settlement with Coeur d’Alene Tribe	13,448		19,185
Other	18,227		14,505
Deferred Tax Liabilities, Gross	691,845		677,229
Total deferred income tax liabilities	489,989		475,481
Current deferred income tax asset	34,281		30,473
Ecova long-term deferred income tax asset	607	[1]	0	[1]
Long-term deferred income tax liability	$ 524,877		$ 505,954

[1] Ecova files its own tax return and its deferred tax assets and liabilities cannot be netted with Avista Corp.'s deferred income tax assets and liabilities. This balance is included in other deferred charges on the Consolidated Balance Sheet at December 31, 2012.