Basis of presentation (Policies)	3 Months Ended
Basis of presentation (Policies)	Mar. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP) for interim financial information, the instructions to SEC Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In preparing the unaudited condensed consolidated financial statements, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the balance sheet and the reported amounts of revenues and expenses for the period. Actual results could differ significantly from those estimates.
Recent accounting pronouncements	Recent accounting pronouncements. Income Taxes. In December 2023, the FASB issued Accounting Standards Update No. 2023-09, Income Taxes (Topic 740): Improvement to Income Tax Disclosures to enhance the transparency and decision usefulness of income tax disclosures. The amendments are effective for annual periods beginning after December 15, 2024. These amendments apply on a prospective basis with a retrospective option. Early adoption is permitted. The Company is currently evaluating the impact of this amendment on the Company’s consolidated financial statements and does not expect the adoption to have a material impact on its consolidated financial statements. Climate-related disclosures. In March 2024, the SEC issued final climate-related disclosure rules under SEC Release No. 33-11275, The Enhancement and Standardization of Climate-Related Disclosures for Investors (climate disclosure rules). The rules will require annual disclosure of material greenhouse gas emissions as well as disclosure of governance, risk management and strategy related to material climate-related risks. In addition, the rules require (i) financial statement impacts of severe weather events and other natural conditions; (ii) a roll forward of carbon offset and renewable energy credit balances if material to the Company’s plan to achieve climate-related targets or goals; and (iii) material impacts on estimates and assumptions in the financial statements. The disclosure requirements will begin phasing in for annual periods beginning with calendar year 2025. In April 2024, the SEC voluntarily stayed implementation of its climate disclosure rules pending completion of judicial review by the Court of Appeals for the Eighth Circuit. In March 2025, the SEC voted to end its defense of its new rules requiring disclosure of climate-related risks and greenhouse gas emissions. The Company is monitoring further SEC developments and final rulings with respect to the applicability of this final rule.
Reclassifications	Reclassifications. Within the condensed consolidated statements of cash flows of prior year, wildfire tort-related claims amounts were reclassified from “Change in other assets and liabilities” to “Decrease in wildfire tort-related claims” for the Company and the Utilities, to conform to the current year financial statement presentation. Reclassifications did not affect previously reported net income, retained earnings or net cash provided by operating activities.
Fair value measurements	The following are descriptions of the valuation methodologies used for assets and liabilities recorded at fair value and for estimating fair value for financial instruments not carried at fair value: Money market mutual funds. The Company considers all liquid investments purchased with an initial maturity of three months or less and deposits in money market mutual funds that are readily convertible into cash to be cash equivalents. The carrying value of cash and cash equivalents approximates fair value due to the short-term nature of these instruments. Short-term borrowings. The carrying amount of short-term borrowings approximated fair value because of the short maturity of these instruments. Long-term debt. Fair value of fixed-rate long-term debt was obtained from third-party financial services providers based on the current rates offered for debt of the same or similar remaining maturities and from discounting the future cash flows using the current rates offered for debt of the same or similar risks, terms, and remaining maturities. The carrying amount of floating rate long-term debt approximated fair value because of the short-term interest reset periods. Long-term debt is classified in Level 2 of the valuation hierarchy. Interest rate swaps. The Company measures its interest rate swaps at fair value. The fair values of the Company's interest rate swaps are based on the estimated amounts that the Company would receive or pay to terminate the contracts at the reporting date and are determined using interest rate pricing models and interest rate related observable inputs. The fair values of the Company's interest rate swaps are classified as a Level 2 measurements.