Regulatory Matters (Schedule Of Asset And Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Regulated Asset Liability [Line Items]
Earning a return, asset	$ 298,173
Not earning a return, asset	312,688
Pending regulatory treatment, asset	52,045
Regulatory Assets, Current	48,552	$ 44,750
Non-current regulatory assets	614,354	619,399
Earning a return, liability	853,126
Not earning a return, liability	20,604
Pending Regulatory Treatment Liability	20,180
Regulatory Liability, Current	113,209	48,264
Non-current regulatory liabilities	780,701	800,089
Excess Deferred Income Taxes Non-plant Related [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities	18,500
Natural Gas Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	40,713
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory Liability, Current	40,713	37,474
Non-current regulatory liabilities	0	0
Power Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	42,005
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory Liability, Current	25,072	5,816
Non-current regulatory liabilities	16,933	24,057
Removal Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	297,379
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory Liability, Current	0	0
Non-current regulatory liabilities	297,379	285,786
Deferred Income Tax Charge [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	436,404
Not earning a return, liability	16,900
Pending Regulatory Treatment Liability	306
Regulatory Liability, Current	27,997	0
Non-current regulatory liabilities	425,613	460,542
Regulatory Liabilities	$ 453,610	460,542
Decoupling [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory liability	2 years
Earning a return, liability	$ 6,986
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory Liability, Current	6,782	0
Non-current regulatory liabilities	204	5,816
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	17,280
Not earning a return, liability	3,704
Pending Regulatory Treatment Liability	4,155
Regulatory Liability, Current	12,645	4,974
Non-current regulatory liabilities	12,494	5,250
Deferred Income Tax Charge [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	91,188
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory Assets, Current	0	0
Non-current regulatory assets	91,188	90,315
Total, asset	91,188	90,315
Pension and Other Postretirement Plans Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	228,062
Pending regulatory treatment, asset	0
Regulatory Assets, Current	0	0
Non-current regulatory assets	228,062	209,115
Unamortized Debt Repurchase Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	10,255
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory Assets, Current	0	0
Non-current regulatory assets	$ 10,255	0
Regulatory Asset For Settlement With Coeur d'Alene Tribe [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	41 years
Earning a return, asset	$ 42,643
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory Assets, Current	0	0
Non-current regulatory assets	42,643	43,954
Demand Side Management Programs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	19,674
Pending regulatory treatment, asset	0
Regulatory Assets, Current	0	0
Non-current regulatory assets	$ 19,674	24,620
Decoupling [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2 years
Earning a return, asset	$ 20,909
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory Assets, Current	3,408	19,759
Non-current regulatory assets	17,501	2,600
Asset Impairment for Regulatory Action [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	24,334
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory Assets, Current	0	0
Non-current regulatory assets	24,334	24,330
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	14,555
Not earning a return, asset	6,658
Pending regulatory treatment, asset	12,480
Regulatory Assets, Current	3,716	0
Non-current regulatory assets	$ 29,977	35,794
Avista Utilities [Member]
Regulated Asset Liability [Line Items]
Tax Cuts and Jobs Act Period to Return Plant Related Excess Deferred Income Taxes	36 years
Alaska Electric Light & Power [Member]
Regulated Asset Liability [Line Items]
Tax Cuts and Jobs Act Period to Return Plant Related Excess Deferred Income Taxes	40 years
Commodity Contract [Member] | Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	$ 0
Not earning a return, asset	58,294
Pending regulatory treatment, asset	0
Regulatory Assets, Current	41,428	24,991
Non-current regulatory assets	16,866	18,967
Interest Rate Swap [Member] | Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	12,359
Not earning a return, liability	0
Pending Regulatory Treatment Liability	15,719
Regulatory Liability, Current	0	0
Non-current regulatory liabilities	28,078	18,638
Interest Rate Swap [Member] | Deferred Derivative Gain (Loss) [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	94,289
Not earning a return, asset	0
Pending regulatory treatment, asset	39,565
Regulatory Assets, Current	0	0
Non-current regulatory assets	$ 133,854	$ 169,704