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Retirement benefits - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2023 | Mar. 31, 2022 | Dec. 31, 2022
Retirement benefits |  |  |
Contributions made to defined benefit plans | $ 2.0 | $ 10.0 |
Contributions expected to be paid in current year | 8.0 |  | $ 43.0
Expected payments for remainder of fiscal year | 3.0 |  | 2.0
Retirement benefits expense | $ 11.0 | 12.0 |
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case (in years) | 5 years |  |
Defined contribution plan, expenses recognized | $ 2.7 | 2.0 |
Cash contributions by the employer to defined contribution plan | 2.7 | 1.9 |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |
Retirement benefits |  |  |
Contributions made to defined benefit plans | 2.0 | 10.0 |
Contributions expected to be paid in current year | 8.0 |  | 42.0
Expected payments for remainder of fiscal year | 1.0 |  | $ 1.0
Retirement benefits expense | 11.0 | 12.0 |
Defined contribution plan, expenses recognized | 1.3 | 0.9 |
Cash contributions by the employer to defined contribution plan | $ 1.3 | $ 0.9 |

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