Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2024
Significant Accounting Policies
Presentation	Presentation—We prepared our accompanying unaudited condensed consolidated financial statements in accordance with accounting principles generally accepted in the United States (“U.S.”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X promulgated by the U.S. Securities and Exchange Commission. Pursuant to such rules and regulations, these financial statements do not include all disclosures required by accounting principles generally accepted in the U.S. for complete financial statements. The condensed consolidated financial statements reflect all adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. Such adjustments are considered to be of a normal recurring nature unless otherwise noted. Operating results for the three and six months ended June 30, 2024, are not necessarily indicative of the results that may be expected for the year ending December 31, 2024, or for any future period. The accompanying condensed consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto as of December 31, 2023 and 2022, and for each of the three years in the period ended December 31, 2023, included in our annual report on Form 10K filed on February 21, 2024.
Accounting estimates	Accounting estimates—To prepare financial statements in accordance with accounting principles generally accepted in the U.S., we must make judgments by applying estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosures of contingent assets and liabilities. On an ongoing basis, we evaluate our estimates and assumptions, including those related to our income taxes, property and equipment, equity investments, contingencies, allowance for excess materials and supplies, postemployment benefit plans and share-based compensation. We base our estimates and assumptions on historical experience and other factors that we believe are reasonable. Actual results could differ from such estimates.
Fair value measurements	Fair value measurements—We estimate fair value at an exchange price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants. Our valuation techniques require inputs that we categorize using a three-level hierarchy, from highest to lowest level of observable inputs, as follows: (1) significant observable inputs, including unadjusted quoted prices for identical assets or liabilities in active markets (“Level 1”), (2) significant other observable inputs, including direct or indirect market data for similar assets or liabilities in active markets or identical assets or liabilities in less active markets (“Level 2”) and (3) significant unobservable inputs, including those that require considerable judgment for which there is little or no market data (“Level 3”). When a valuation requires multiple input levels, we categorize the entire fair value measurement according to the lowest level of input that is significant to the measurement even though we may have also utilized significant inputs that are more readily observable.
Accounting standards updates	Recently issued accounting standards updates not yet adopted Segment reporting—Effective for the year ending December 31, 2024, we will adopt the accounting standards update that requires incremental disclosures about a public entity’s reportable segments but does not change the definition or guidance for determining reportable segments. The update, which explicitly applies to entities such as us with a single reportable segment, requires disclosure of the significant expense categories and amounts that are regularly provided to the chief operating decision-maker and included in the reported measure of segment profit or loss. Additionally, the update requires disclosures about the individual or the group or committee identified as the chief operating decision-maker. We will provide the new disclosures, as required, in our annual report for the year ending December 31, 2024 and interim periods thereafter with retrospective application to all periods presented, unless impracticable. Although our adoption of the update will require us to augment certain disclosures in the notes to consolidated financial statements, we do not expect such adoption to have a material effect on our consolidated statements of financial position, operations or cash flows. Income taxes—Effective no later than January 1, 2025, we will adopt the accounting standards update that requires significant additional disclosures intended to enhance the transparency and decision usefulness of income tax disclosures, particularly in the rate reconciliation table and disclosures about income taxes paid. The new guidance will be applied prospectively and permits, but does not require, retrospective application. The update, which permits early adoption, is effective for annual periods beginning after December 15, 2024. We continue to evaluate the requirements. Although we expect our adoption will require us to augment certain disclosures in our notes to consolidated financial statements, we do not expect our adoption to have a material effect on our consolidated statements of financial position, operations or cash flows.

Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2024

Presentation—We prepared our accompanying unaudited condensed consolidated financial statements in accordance with accounting principles generally accepted in the United States (“U.S.”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X promulgated by the U.S. Securities and Exchange Commission. Pursuant to such rules and regulations, these financial statements do not include all disclosures required by accounting principles generally accepted in the U.S. for complete financial statements. The condensed consolidated financial statements reflect all adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. Such adjustments are considered to be of a normal recurring nature unless otherwise noted. Operating results for the three and six months ended June 30, 2024, are not necessarily indicative of the results that may be expected for the year ending December 31, 2024, or for any future period. The accompanying condensed consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto as of December 31, 2023 and 2022, and for each of the three years in the period ended December 31, 2023, included in our annual report on Form 10K filed on February 21, 2024.

Accounting estimates

Accounting estimates—To prepare financial statements in accordance with accounting principles generally accepted in the U.S., we must make judgments by applying estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosures of contingent assets and liabilities. On an ongoing basis, we evaluate our estimates and assumptions, including those related to our income taxes, property and equipment, equity investments, contingencies, allowance for excess materials and supplies, postemployment benefit plans and share-based compensation. We base our estimates and assumptions on historical experience and other factors that we believe are reasonable. Actual results could differ from such estimates.

Fair value measurements

Fair value measurements—We estimate fair value at an exchange price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants. Our valuation techniques require inputs that we categorize using a three-level hierarchy, from highest to lowest level of observable inputs, as follows: (1) significant observable inputs, including unadjusted quoted prices for identical assets or liabilities in active markets (“Level 1”), (2) significant other observable inputs, including direct or indirect market data for similar assets or liabilities in active markets or identical assets or liabilities in less active markets (“Level 2”) and (3) significant unobservable inputs, including those that require considerable judgment for which there is little or no market data (“Level 3”). When a valuation requires multiple input levels, we categorize the entire fair value measurement according to the lowest level of input that is significant to the measurement even though we may have also utilized significant inputs that are more readily observable.

Accounting standards updates

Recently issued accounting standards updates not yet adopted

Segment reporting—Effective for the year ending December 31, 2024, we will adopt the accounting standards update that requires incremental disclosures about a public entity’s reportable segments but does not change the definition or guidance for determining reportable segments. The update, which explicitly applies to entities such as us with a single reportable segment, requires disclosure of the significant expense categories and amounts that are regularly provided to the chief operating decision-maker and included in the reported measure of segment profit or loss. Additionally, the update requires disclosures about the individual or the group or committee identified as the chief operating decision-maker. We will provide the new disclosures, as required, in our annual report for the year ending December 31, 2024 and interim periods thereafter with retrospective application to all periods presented, unless impracticable. Although our adoption of the update will require us to augment certain disclosures in the notes to consolidated financial statements, we do not expect such adoption to have a material effect on our consolidated statements of financial position, operations or cash flows.

Income taxes—Effective no later than January 1, 2025, we will adopt the accounting standards update that requires significant additional disclosures intended to enhance the transparency and decision usefulness of income tax disclosures, particularly in the rate reconciliation table and disclosures about income taxes paid. The new guidance will be applied prospectively and permits, but does not require, retrospective application. The update, which permits early adoption, is effective for annual periods beginning after December 15, 2024. We continue to evaluate the requirements. Although we expect our adoption will require us to augment certain disclosures in our notes to consolidated financial statements, we do not expect our adoption to have a material effect on our consolidated statements of financial position, operations or cash flows.