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Regulatory Matters: Rate Review (Details) $ in Thousands | Mar. 01, 2021 USD ($) | Jan. 26, 2021 USD ($) mi | Sep. 11, 2020 | Jan. 06, 2021 mi | Dec. 30, 2020 USD ($)
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Colorado Public Utilities Commission (CPUC) | Colorado Electric |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Settlement of plan to provide TCJA-related customer billing credits to its customers |  |  |  |  | $ 9,300
Nebraska Public Service Commission (NPSC) | Nebraska Gas |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Tax Cuts and Jobs Act, Income Tax Expense (Benefit) |  | $ 2,900 |  |  |
Nebraska Publc Service Commission (NPSC) | Nebraska Gas |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage | 50.00% |  |  |  |
Public Utilities, Approved Debt Capital Structure, Percentage | 50.00% |  |  |  |
Public Utilities, Approved Return on Equity, Percentage | 9.50% |  |  |  |
Public Utilities, Term Extension of System Saftey and Integrity Rider | 5 years |  |  |  |
Rate Review Filed with the Regulatory Agency | Colorado Public Utilities Commission (CPUC) | Colorado Gas |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Public Utilities, Term Extension of System Saftey and Integrity Rider |  |  | 5 years |  |
Rate Review Filed with the Regulatory Agency | Nebraska Publc Service Commission (NPSC) | Nebraska Gas |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Public Utilities - Length of Natural Gas Pipeline to Receive Infrastructure Investments | mi |  | 13,000 |  |  |
Public Utilities Amount of System Safety and Integrety Rider Moved to Base Rates | $ 4,600 |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount | $ 6,500 |  |  |  |
Rate Review Dismissed by Regulatory Agency | Colorado Public Utilities Commission (CPUC) | Colorado Gas |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Public Utilities - Length of Natural Gas Pipeline to Receive Infrastructure Investments | mi |  |  |  | 7,000 |

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