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Revenue Revenue Disaggregation of Revenue (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Disaggregation of Revenue [Line Items] |  |
Revenues | $ 409,361 | $ 436,470
Residential Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 121,291 |
Commercial and Governmental Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 86,953 |
Industrial Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 25,119 |
Public Street and Highway Lighting Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 1,927 |
Total Retail Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 235,290 |
Electric Transmission [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 3,830 |
Other Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 6,291 |
Total Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 245,411 |
Residential Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 80,653 |
Commercial Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 37,373 |
Industrial and Interruptible Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 1,683 |
Total Retail Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 119,709 |
Transportation Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 2,567 |
Other Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 1,125 |
Total Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 123,401 |
Avista Utilities [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 388,754 |
Avista Utilities [Member] | Residential Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 114,753 |
Avista Utilities [Member] | Commercial and Governmental Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 78,909 |
Avista Utilities [Member] | Industrial Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 25,119 |
Avista Utilities [Member] | Public Street and Highway Lighting Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 1,859 |
Avista Utilities [Member] | Total Retail Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 220,640 |
Avista Utilities [Member] | Electric Transmission [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 3,830 |
Avista Utilities [Member] | Other Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 6,291 |
Avista Utilities [Member] | Total Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 230,761 |
Avista Utilities [Member] | Residential Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 80,653 |
Avista Utilities [Member] | Commercial Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 37,373 |
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 1,683 |
Avista Utilities [Member] | Total Retail Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 119,709 |
Avista Utilities [Member] | Transportation Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 2,567 |
Avista Utilities [Member] | Other Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 1,125 |
Avista Utilities [Member] | Total Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 123,401 |
Avista Utilities [Member] | Revenue from Contracts with Customers [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 354,162 |
Avista Utilities [Member] | Derivative Revenues [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 58,392 |
Avista Utilities [Member] | Alternative Revenue Programs [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (5,939) |
Avista Utilities [Member] | Provision for Rate Refunds [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (19,822) |
Avista Utilities [Member] | Other Utility Revenues [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 1,961 |
Alaska Electric Light & Power [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 13,663 |
Alaska Electric Light & Power [Member] | Residential Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 6,538 |
Alaska Electric Light & Power [Member] | Commercial and Governmental Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 8,044 |
Alaska Electric Light & Power [Member] | Industrial Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Public Street and Highway Lighting Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 68 |
Alaska Electric Light & Power [Member] | Total Retail Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 14,650 |
Alaska Electric Light & Power [Member] | Electric Transmission [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Other Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Total Electric [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 14,650 |
Alaska Electric Light & Power [Member] | Residential Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Commercial Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Industrial and Interruptible Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Total Retail Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Transportation Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Other Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Total Natural Gas [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenue from Contract with Customer, Including Assessed Tax | 0 |
Alaska Electric Light & Power [Member] | Revenue from Contracts with Customers [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 14,650 |
Alaska Electric Light & Power [Member] | Provision for Rate Refunds [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (1,122) |
Alaska Electric Light & Power [Member] | Other Utility Revenues [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 135 |
Corporate and Other [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 6,944 |
Corporate and Other [Member] | Revenue from Contracts with Customers [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 6,729 |
Corporate and Other [Member] | Other Revenues [Member] |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | $ 215 |

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