Nature of Operations and Basis of Presentation	3 Months Ended
Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations and Basis of Presentation	Nature of Operations and Basis of Presentation The accompanying Unaudited Condensed Consolidated Financial Statements include the accounts of NACCO Industries, Inc.® (“NACCO” or the "Company"). NACCO, through a portfolio of mining and natural resources businesses, operates under three business segments: Coal Mining, North American Mining ("NAMining") and Minerals Management. The Coal Mining segment operates surface coal mines under long-term contracts with power generation companies and an activated carbon producer pursuant to a service-based business model. The NAMining segment provides value-added contract mining and other services for producers of aggregates, lithium and other minerals. The Minerals Management segment acquires and promotes the development of oil, gas and coal mineral interests, generating income primarily from royalty-based lease payments from third parties. In addition, the Company has a business providing stream and wetland mitigation solutions. The Company also has unallocated items not directly attributable to a reportable segment. Intercompany accounts and transactions are eliminated in consolidation. See Note 8 to the Unaudited Condensed Consolidated Financial Statements for further discussion of segment reporting. The Company’s operating segments are further described below: Coal Mining Segment During the three months ended March 31, 2021, the Company's operating coal mines were: Bisti Fuels Company, LLC (“Bisti”), The Coteau Properties Company (“Coteau”), Coyote Creek Mining Company, LLC (“Coyote Creek”), Demery Resources Company, LLC (“Demery”), The Falkirk Mining Company (“Falkirk”), Mississippi Lignite Mining Company (“MLMC”) and The Sabine Mining Company (“Sabine”). The Company operates these mines as the North American Coal Corporation® ("NACoal"). Bisti supplies the Four Corners Power Plant through its contract mining agreement with the Navajo Transitional Energy Company. On March 12, 2021, the Arizona Public Service Co., an owner and operator of the Four Corners Power Plant, announced plans to begin operating the plant seasonally starting in the fall of 2023, with one of the plant’s two remaining units operating year-round and the other operating only during June through October. Under seasonal operation of the power plant, future deliveries are expected to be in the range of 3.3 million to 3.5 million tons annually, beginning in 2024 through the end of the term of the contract mining agreement in 2031. Bisti delivered 4.2 million and 5.0 million tons in 2020 and 2019, respectively. Sabine operates the Sabine Mine in Texas. All production from Sabine is delivered to Southwestern Electric Power Company's (“SWEPCO”) Henry W. Pirkey Plant (the “Pirkey Plant”). SWEPCO is an American Electric Power (“AEP”) company. During 2020, AEP announced it intends to retire the Pirkey Plant in 2023 in order to comply with the U.S. Environmental Protection Agency’s Coal Combustion Residuals rule. SWEPCO expects deliveries from Sabine to continue until the first quarter of 2023 at which time Sabine expects to begin final reclamation. Mine reclamation is the responsibility of SWEPCO. Coteau operates the Freedom Mine in North Dakota. All coal production from the Freedom Mine is delivered to Basin Electric Power Cooperative (“Basin Electric”). Basin Electric utilizes the coal at the Great Plains Synfuels Plant (the “Synfuels Plant”), Antelope Valley Station and Leland Olds Station. The Synfuels Plant is a coal gasification plant that manufactures synthetic natural gas and produces fertilizers, solvents, phenol, carbon dioxide, and other chemical products for sale. During 2020, Basin Electric informed its employees and Coteau that it is considering changes that may result in modifications to its Synfuels Plant that could potentially reduce or eliminate coal requirements at the Synfuels Plant beginning in 2026. Basin Electric indicated that if it decides to proceed with any changes that could reduce or eliminate the use of coal, the feedstock change is not expected to occur before 2026. As a result, coal deliveries to the Synfuels Plant are expected to continue until at least 2026. Deliveries to Antelope Valley Station and Leland Olds Station are expected to continue through the end of the existing coal sales agreement, which can be extended through 2037 at the option of the Company. During 2020, Great River Energy ("GRE"), Falkirk's customer and the Company's second largest customer, announced its intent to retire the Coal Creek Station power plant in the second half of 2022. Falkirk is the sole supplier of lignite coal to Coal Creek Station pursuant to a long-term contract, which specifies that GRE is responsible for all costs related to mine closure, including mine reclamation. GRE has announced that it is in exclusive negotiations with a third party to sell Coal Creek Station. If GRE's efforts to sell the power plant are successful, the Company expects to continue to operate the Falkirk Mine, however the terms of the existing mining contract could change. At all operating coal mines other than MLMC, the Company is paid a management fee per ton of coal or heating unit (MMBtu) delivered. Each contract specifies the indices and mechanics by which fees change over time, generally in line with broad measures of U.S. inflation. The customers are responsible for funding all mine operating costs, including final mine reclamation, and directly or indirectly provide all of the capital required to build and operate the mine. This contract structure eliminates exposure to spot coal market price fluctuations while providing steady income and cash flow with minimal capital investment. Other than at Coyote Creek, debt financing provided by or supported by the customers is without recourse to NACCO and NACoal. See Note 6 for further discussion of Coyote Creek's guarantees. All operating coal mines other than MLMC meet the definition of a variable interest entity (“VIE”). In each case, NACCO is not the primary beneficiary of the VIE as it does not exercise financial control; therefore, NACCO does not consolidate the results of these operations within its financial statements. Instead, these contracts are accounted for as equity method investments. The income before income taxes associated with these VIE's is reported as Earnings of unconsolidated operations on the Unaudited Condensed Consolidated Statements of Operations and the Company’s investment is reported on the line Investments in Unconsolidated Subsidiaries in the Unaudited Condensed Consolidated Balance Sheets. The mines that meet the definition of a VIE are referred to collectively as the “Unconsolidated Subsidiaries.” For tax purposes, the Unconsolidated Subsidiaries are included within the NACCO consolidated U.S. tax return; therefore, the income tax expense line on the Unaudited Condensed Consolidated Statements of Operations includes income taxes related to these entities. See Note 6 for further information on the Unconsolidated Subsidiaries. The MLMC contract is the only operating coal contract in which the Company is responsible for all operating costs, capital requirements and final mine reclamation; therefore, MLMC is consolidated within NACCO’s financial statements. MLMC sells coal to its customer at a contractually agreed-upon price which adjusts monthly, primarily based on changes in the level of established indices which reflect general U.S. inflation rates. Caddo Creek Resources Company, LLC (“Caddo Creek”) ceased all mining and delivery of lignite and commenced mine reclamation in the fourth quarter of 2020. The financial results of Caddo Creek are consolidated within NACCO's financial statements for the three months ended March 31, 2021. Prior to entering into reclamation, Caddo Creek met the definition of a VIE; therefore, the financial results of Caddo Creek are reported as Earnings of unconsolidated operations for the three months ended March 31, 2020. The reclamation at Caddo Creek is expected to be substantially complete in 2022. NAMining Segment The NAMining segment provides value-added contract mining and other services for producers of aggregates, lithium and other minerals. The segment is a primary platform for the Company’s growth and diversification of mining activities outside of the coal industry. NAMining provides contract mining services for independently owned mines and quarries, creating value for its customers by performing the mining aspects of its customers’ operations. This allows customers to focus on their areas of expertise: materials handling and processing, product sales and distribution. NAMining operates primarily at limestone quarries in Florida, but is focused on expanding outside of Florida and into mining materials other than limestone. In addition, NAMining will serve as exclusive contract miner for the Thacker Pass lithium project in northern Nevada. NAMining utilizes both fixed price and management fee contract structures. Certain of the entities within the NAMining segment are VIEs and are accounted for under the equity method as Unconsolidated Subsidiaries. See Note 6 for further discussion. Minerals Management Segment The Minerals Management segment derives income primarily by leasing its royalty and mineral interests to third-party exploration and production companies, and, to a lesser extent, other mining companies, granting them the rights to explore, develop, mine, produce, market and sell gas, oil, and coal in exchange for royalty payments based on the lessees' sales of those minerals. During 2020, the Minerals Management segment acquired mineral interests in the Permian Basin in Texas and intends to make future acquisitions of mineral and royalty interests that meet the Company’s acquisition criteria as part of its growth strategy. The Company’s legacy royalty and mineral interests are located in Ohio (Utica and Marcellus shale natural gas), Louisiana (Haynesville shale and Cotton Valley formation natural gas), Texas (Cotton Valley and Austin Chalk formation natural gas), Mississippi (coal), Pennsylvania (coal, coalbed methane and Marcellus shale natural gas), Alabama (coal and coalbed methane and natural gas) and North Dakota (coal, oil and natural gas). The majority of the Company’s legacy reserves were acquired as part of its historical coal mining operations. Specialized employees in the Minerals Management segment also provide surface and mineral acquisition and lease maintenance services related to Company operations. Basis of Presentation: These financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the financial position of the Company at March 31, 2021, the results of its operations, comprehensive income, cash flows and changes in equity for the three months ended March 31, 2021 and 2020 have been included. These Unaudited Condensed Consolidated Financial Statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020. The balance sheet at December 31, 2020 has been derived from the audited financial statements at that date but does not include all of the information or notes required by U.S. GAAP for complete financial statements. Certain amounts in prior period Unaudited Condensed Consolidated Financial Statements have been reclassified to conform to the current period's presentation.

The accompanying Unaudited Condensed Consolidated Financial Statements include the accounts of NACCO Industries, Inc.® (“NACCO” or the "Company"). NACCO, through a portfolio of mining and natural resources businesses, operates under three business segments: Coal Mining, North American Mining ("NAMining") and Minerals Management. The Coal Mining segment operates surface coal mines under long-term contracts with power generation companies and an activated carbon producer pursuant to a service-based business model. The NAMining segment provides value-added contract mining and other services for producers of aggregates, lithium and other minerals. The Minerals Management segment acquires and promotes the development of oil, gas and coal mineral interests, generating income primarily from royalty-based lease payments from third parties. In addition, the Company has a business providing stream and wetland mitigation solutions.

The Company also has unallocated items not directly attributable to a reportable segment. Intercompany accounts and transactions are eliminated in consolidation. See Note 8 to the Unaudited Condensed Consolidated Financial Statements for further discussion of segment reporting.

During the three months ended March 31, 2021, the Company's operating coal mines were: Bisti Fuels Company, LLC (“Bisti”), The Coteau Properties Company (“Coteau”), Coyote Creek Mining Company, LLC (“Coyote Creek”), Demery Resources Company, LLC (“Demery”), The Falkirk Mining Company (“Falkirk”), Mississippi Lignite Mining Company (“MLMC”) and The Sabine Mining Company (“Sabine”). The Company operates these mines as the North American Coal Corporation® ("NACoal").

Bisti supplies the Four Corners Power Plant through its contract mining agreement with the Navajo Transitional Energy Company. On March 12, 2021, the Arizona Public Service Co., an owner and operator of the Four Corners Power Plant, announced plans to begin operating the plant seasonally starting in the fall of 2023, with one of the plant’s two remaining units operating year-round and the other operating only during June through October. Under seasonal operation of the power plant, future deliveries are expected to be in the range of 3.3 million to 3.5 million tons annually, beginning in 2024 through the end of the term of the contract mining agreement in 2031. Bisti delivered 4.2 million and 5.0 million tons in 2020 and 2019, respectively.

Sabine operates the Sabine Mine in Texas. All production from Sabine is delivered to Southwestern Electric Power Company's (“SWEPCO”) Henry W. Pirkey Plant (the “Pirkey Plant”). SWEPCO is an American Electric Power (“AEP”) company. During 2020, AEP announced it intends to retire the Pirkey Plant in 2023 in order to comply with the U.S. Environmental Protection Agency’s Coal Combustion Residuals rule. SWEPCO expects deliveries from Sabine to continue until the first quarter of 2023 at which time Sabine expects to begin final reclamation. Mine reclamation is the responsibility of SWEPCO.

Coteau operates the Freedom Mine in North Dakota. All coal production from the Freedom Mine is delivered to Basin Electric Power Cooperative (“Basin Electric”). Basin Electric utilizes the coal at the Great Plains Synfuels Plant (the “Synfuels Plant”), Antelope Valley Station and Leland Olds Station. The Synfuels Plant is a coal gasification plant that manufactures synthetic natural gas and produces fertilizers, solvents, phenol, carbon dioxide, and other chemical products for sale. During 2020, Basin Electric informed its employees and Coteau that it is considering changes that may result in modifications to its Synfuels Plant that could potentially reduce or eliminate coal requirements at the Synfuels Plant beginning in 2026. Basin Electric indicated that if it decides to proceed with any changes that could reduce or eliminate the use of coal, the feedstock change is not expected to occur before 2026. As a result, coal deliveries to the Synfuels Plant are expected to continue until at least 2026. Deliveries to Antelope Valley Station and Leland Olds Station are expected to continue through the end of the existing coal sales agreement, which can be extended through 2037 at the option of the Company.

During 2020, Great River Energy ("GRE"), Falkirk's customer and the Company's second largest customer, announced its intent to retire the Coal Creek Station power plant in the second half of 2022. Falkirk is the sole supplier of lignite coal to Coal Creek Station pursuant to a long-term contract, which specifies that GRE is responsible for all costs related to mine closure, including mine reclamation. GRE has announced that it is in exclusive negotiations with a third party to sell Coal Creek Station. If GRE's efforts to sell the power plant are successful, the Company expects to continue to operate the Falkirk Mine, however the terms

At all operating coal mines other than MLMC, the Company is paid a management fee per ton of coal or heating unit (MMBtu) delivered. Each contract specifies the indices and mechanics by which fees change over time, generally in line with broad measures of U.S. inflation. The customers are responsible for funding all mine operating costs, including final mine reclamation, and directly or indirectly provide all of the capital required to build and operate the mine. This contract structure eliminates exposure to spot coal market price fluctuations while providing steady income and cash flow with minimal capital investment. Other than at Coyote Creek, debt financing provided by or supported by the customers is without recourse to NACCO and NACoal. See Note 6 for further discussion of Coyote Creek's guarantees.

All operating coal mines other than MLMC meet the definition of a variable interest entity (“VIE”). In each case, NACCO is not the primary beneficiary of the VIE as it does not exercise financial control; therefore, NACCO does not consolidate the results of these operations within its financial statements. Instead, these contracts are accounted for as equity method investments. The income before income taxes associated with these VIE's is reported as Earnings of unconsolidated operations on the Unaudited Condensed Consolidated Statements of Operations and the Company’s investment is reported on the line Investments in Unconsolidated Subsidiaries in the Unaudited Condensed Consolidated Balance Sheets. The mines that meet the definition of a VIE are referred to collectively as the “Unconsolidated Subsidiaries.” For tax purposes, the Unconsolidated Subsidiaries are included within the NACCO consolidated U.S. tax return; therefore, the income tax expense line on the Unaudited Condensed Consolidated Statements of Operations includes income taxes related to these entities. See Note 6 for further information on the Unconsolidated Subsidiaries.

The MLMC contract is the only operating coal contract in which the Company is responsible for all operating costs, capital requirements and final mine reclamation; therefore, MLMC is consolidated within NACCO’s financial statements. MLMC sells coal to its customer at a contractually agreed-upon price which adjusts monthly, primarily based on changes in the level of established indices which reflect general U.S. inflation rates.

Caddo Creek Resources Company, LLC (“Caddo Creek”) ceased all mining and delivery of lignite and commenced mine reclamation in the fourth quarter of 2020. The financial results of Caddo Creek are consolidated within NACCO's financial statements for the three months ended March 31, 2021. Prior to entering into reclamation, Caddo Creek met the definition of a VIE; therefore, the financial results of Caddo Creek are reported as Earnings of unconsolidated operations for the three months ended March 31, 2020. The reclamation at Caddo Creek is expected to be substantially complete in 2022.

The NAMining segment provides value-added contract mining and other services for producers of aggregates, lithium and other minerals. The segment is a primary platform for the Company’s growth and diversification of mining activities outside of the coal industry. NAMining provides contract mining services for independently owned mines and quarries, creating value for its customers by performing the mining aspects of its customers’ operations. This allows customers to focus on their areas of expertise: materials handling and processing, product sales and distribution. NAMining operates primarily at limestone quarries in Florida, but is focused on expanding outside of Florida and into mining materials other than limestone. In addition, NAMining will serve as exclusive contract miner for the Thacker Pass lithium project in northern Nevada.

NAMining utilizes both fixed price and management fee contract structures. Certain of the entities within the NAMining segment are VIEs and are accounted for under the equity method as Unconsolidated Subsidiaries. See Note 6 for further discussion.

The Minerals Management segment derives income primarily by leasing its royalty and mineral interests to third-party exploration and production companies, and, to a lesser extent, other mining companies, granting them the rights to explore, develop, mine, produce, market and sell gas, oil, and coal in exchange for royalty payments based on the lessees' sales of those minerals. During 2020, the Minerals Management segment acquired mineral interests in the Permian Basin in Texas and intends to make future acquisitions of mineral and royalty interests that meet the Company’s acquisition criteria as part of its growth strategy.

The Company’s legacy royalty and mineral interests are located in Ohio (Utica and Marcellus shale natural gas), Louisiana (Haynesville shale and Cotton Valley formation natural gas), Texas (Cotton Valley and Austin Chalk formation natural gas), Mississippi (coal), Pennsylvania (coal, coalbed methane and Marcellus shale natural gas), Alabama (coal and coalbed methane and natural gas) and North Dakota (coal, oil and natural gas). The majority of the Company’s legacy reserves were acquired as part of its historical coal mining operations. Specialized employees in the Minerals Management segment also provide surface and mineral acquisition and lease maintenance services related to Company operations.

Basis of Presentation: These financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("U.S. GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the financial position of the Company at March 31, 2021, the results of its operations, comprehensive income, cash flows and changes in equity for the three months ended March 31, 2021 and 2020 have been included. These Unaudited Condensed Consolidated Financial Statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020.