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Regulatory Matters - Summary of Utilities Rate Plans (RECO) (Details) - RECO - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended | 35 Months Ended
--- | --- | --- | --- | ---
Feb. 29, 2020 | Apr. 30, 2017 | Jan. 31, 2016 | Mar. 31, 2017 | Dec. 31, 2017 | Jan. 31, 2020
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Utilities operating expense, depreciation and amortization |  |  |  |  |  | $ 0.2
Regulatory liabilities, amortization period |  |  |  |  |  | 3 years
Amortization to income of net regulatory assets | $ 4.8 |  |  |  |  | $ 25.6
Regulatory assets, amortization period | 4 years |  |  |  |  | 4 years
Average rate base | $ 229.9 |  |  |  |  | $ 178.7
Weighted average cost of capital (after-tax) (percent) | 711.00% |  |  |  |  | 7.47%
Authorized return on common equity (percent) | 950.00% |  |  |  |  | 960.00%
Cost of long-term debt (percent) | 488.00% |  |  |  |  | 537.00%
Common Equity Ratio, Percentage | 4832.00% |  |  |  |  | 4970.00%
FERC |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Requested rate increase (decrease), amount |  | $ 17.7 |  | $ 11.8 |  |
Return on common equity (percent) |  |  |  |  | 10.00% |
Electric |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Plan electric system storm hardening amount |  |  | $ 15.7 |  |  |
Plan period (years) |  |  | 3 years |  |  |
Year 1 |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Base rate changes | $ 12.0 |  |  |  |  | $ 1.7
Actual return on common equity (percent) | 5.40% |  |  |  |  | 7.50%
Year 2 |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Actual return on common equity (percent) |  |  |  |  |  | 5.70%

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