Avista Utilities Regulatory Matters (Schedule Of Asset And Liability) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Regulated Asset Liability [Line Items]
Earning a return, asset	$ 168,615
Not earning a return, asset	211,143
Pending regulatory treatment, asset	4,597
Total, asset	384,355	566,631
Earning a return, liability	280,078
Not earning a return, liability	49,157
Pending Regulatory Treatment Liability	25,046
Total, liability	354,281	318,643
Natural Gas Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	12,075
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Total, liability	12,075	6,917
Power Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	17,904
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Total, liability	17,904	27,323
Removal Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	242,850
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Total, liability	242,850	234,128
Income Tax Related Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	9,203
Pending Regulatory Treatment Liability	0
Total, liability	9,203	17,206
Regulatory Liability for Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	33,543
Pending Regulatory Treatment Liability	0
Total, liability	33,543	7,265
Regulatory Liability For Production Facility [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	0
Pending Regulatory Treatment Liability	25,046
Total, liability	25,046	21,488
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	7,249
Not earning a return, liability	6,411
Pending Regulatory Treatment Liability	0
Total, liability	13,660	4,316
Investment In Exchange Power-Net [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2019
Earning a return, asset	13,883
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	13,883	16,333
Deferred Income Tax Charge [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	71,421
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	71,421	79,406
Pension and Other Postretirement Plans Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	156,984
Pending regulatory treatment, asset	0
Total, asset	156,984	306,408
Current Regulatory Asset For Utility Derivatives [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	10,829
Pending regulatory treatment, asset	0
Total, asset	10,829	35,082
Unamortized Debt Repurchase Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	19,417
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	19,417	21,635
Regulatory Asset For Settlement With Coeur d'Alene Tribe [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2059
Earning a return, asset	49,198
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	49,198	50,509
Demand Side Management Programs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	9,576
Pending regulatory treatment, asset	0
Total, asset	9,576	2,579
Montana Lease Payments [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	3,022
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	3,022	4,059
Lancaster Plant 2010 Net Costs [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2015
Earning a return, asset	2,607
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	2,607	3,967
Deferred Maintenance Costs [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2016
Earning a return, asset	0
Not earning a return, asset	5,813
Pending regulatory treatment, asset	0
Total, asset	5,813	6,312
Power Deferrals Regulatory Asset [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	5,065
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	5,065	0
Regulatory Asset For Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2013
Earning a return, asset	0
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Total, asset	0	1,406
Non Current Regulatory Asset For Utility Derivatives [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	23,258
Pending regulatory treatment, asset	0
Total, asset	23,258	25,218
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	4,002
Not earning a return, asset	4,683
Pending regulatory treatment, asset	4,597
Total, asset	$ 13,282	$ 13,717
Minimum [Member] | Regulatory Liability for Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory liability	2014
Maximum [Member] | Regulatory Liability for Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory liability	2015