Other Events	12 Months Ended
Other Events	Dec. 31, 2021
Other Events [Abstract]
Other Events	Other Events Restructuring Charges From time to time, the Company initiates restructuring activities to appropriately align its cost structure or optimize coal production relative to prevailing market conditions. Costs associated with restructuring actions can include the impact of early mine closures, voluntary and involuntary workforce reductions, office closures and other related activities. Costs associated with restructuring activities amounted to $8.3 million, $37.9 million, and $24.3 million during the years ended December 31, 2021, 2020 and 2019, respectively, and are included as “Restructuring charges” in the Company's consolidated statements of operations. Such costs were primarily associated with voluntary and involuntary workforce reductions. Divestitures and Other Transactions During July 2021, the Company executed transactions to sell its closed Millennium and Wilkie Creek Mines, which reduced its closed mine reclamation liabilities and associated costs. The Millennium Mine was sold for minimal cash consideration and the assumption of the majority of the mine’s reclamation liabilities. The Company will remain responsible for $9.4 million of reclamation liabilities and retains certain royalty rights on future sales. The Company recorded a gain of $26.1 million in connection with the sale, and will recognize royalty revenue when it is deemed collectible. The gain is included within “Net gain on disposals” in the accompanying consolidated statements of operations. The Wilkie Creek Mine was sold for minimal cash consideration and full assumption of the mine’s reclamation liabilities. The Company retains certain royalty rights on future sales. The Company recorded a gain of $24.6 million in connection with the sale, and will recognize royalty revenue when it is deemed collectible. The gain is included within “Income (loss) from discontinued operations, net of income taxes” in the accompanying consolidated statements of operations. United Wambo Joint Venture with Glencore In December 2019 the Company formed an unincorporated joint venture with Glencore plc (Glencore), in which the Company holds a 50% interest, to combine the existing operations of the Company’s Wambo Open-Cut Mine in Australia with the adjacent coal reserves of Glencore’s United Mine. The Company proportionally consolidates the entity based upon its economic interest. Both parties contributed mining tenements upon formation of the joint venture (United Wambo Joint Venture), and combined operations commenced in December 2020. At that date, the parties contributed mining equipment and other assets, and certain additional construction and development activities are ongoing. During the years ended December 31, 2021 and 2020, the Company contributed approximately $59 million and $72 million, respectively, towards construction and development, which is reflected as “Additions to property, plant, equipment and mine development” in the accompanying consolidated statements of cash flows. Glencore is responsible for managing the mining operations of the joint venture. The Company accounted for its interest in the United Wambo Joint Venture at fair value and recognized a gain of $48.1 million, which was classified in “Gain on formation of United Wambo Joint Venture” in the accompanying consolidated statements of operations during the year ended December 31, 2019. North Goonyella The Company’s North Goonyella Mine in Queensland, Australia experienced a fire in 2018 which resulted in the suspension of mining operations. During the years ended December 31, 2019 and 2018, the Company recorded provisions for equipment losses of $83.2 million and $66.4 million, respectively, related to the fire. During 2019, the Company collected a $125 million insurance recovery under a property damage and business interruption policy. The Company has incurred containment and idling costs subsequent to the mine’s suspension which amounted to $13.0 million, $32.3 million and $111.5 million during the years ended December 31, 2021, 2020 and 2019, respectively. The Company is currently evaluating various alternatives regarding the future utility of the mine. In the event that no future mining occurs at the North Goonyella Mine or the Company is unable to find a commercial alternative, the Company may record additional charges for the remaining carrying value of the North Goonyella Mine of up to approximately $0.3 billion, which is included in the at-risk value described in Note 3. “Asset Impairment.” Incremental exposures above the aforementioned include take-or-pay obligations and other costs associated with idling or closing the mine.