Warrior Met Coal (HCC) 10-Q 30 Oct 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Oct. 28, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-38061
Entity Registrant Name	Warrior Met Coal, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-0706839
Entity Address, Address Line One	16243 Highway 216
Entity Address, City or Town	Brookwood
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35444
City Area Code	205
Local Phone Number	554-6150
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	HCC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		51,071,608
Entity Central Index key	0001691303
Document Fiscal Year Focus	2019
Amendment Flag	false
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 287,506,000	$ 273,304,000	$ 1,063,408,000	$ 1,017,647,000
Costs and expenses:
Cost of sales (exclusive of items shown separately below)	190,221,000	167,188,000	578,038,000	536,407,000
Cost of other revenues (exclusive of items shown separately below)	7,583,000	6,704,000	23,346,000	21,826,000
Depreciation and depletion	25,741,000	26,071,000	73,652,000	71,750,000
Selling, general and administrative	9,362,000	7,357,000	29,050,000	29,056,000
Transaction and other expenses	0	3,265,000	0	7,539,000
Total costs and expenses	232,907,000	210,585,000	704,086,000	666,578,000
Operating income	54,599,000	62,719,000	359,322,000	351,069,000
Interest expense, net	(7,250,000)	(10,128,000)	(22,793,000)	(28,472,000)
Loss on early extinguishment of debt	0	0	(9,756,000)	0
Other income	5,272,000	0	22,815,000	0
Income before income tax expense	52,621,000	52,591,000	349,588,000	322,597,000
Income tax expense	7,599,000	0	68,639,000	0
Net income	$ 45,022,000	$ 52,591,000	$ 280,949,000	$ 322,597,000
Basic and diluted net income per share:
Net income per share—basic (in dollars per share)	$ 0.88	$ 1	$ 5.46	$ 6.10
Net income per share—diluted (in dollars per share)	$ 0.87	$ 1	$ 5.44	$ 6.09
Weighted average number of shares outstanding—basic (in shares)	51,348	52,707	51,469	52,916
Weighted average number of shares outstanding—diluted (in shares)	51,482	52,708	51,599	52,945
Dividends per share (in dollars per share)	$ 0.05	$ 0.05	$ 4.56	$ 6.68
Sales
Revenues:
Total revenues	$ 280,841,000	$ 264,908,000	$ 1,037,950,000	$ 992,832,000
Other revenues
Revenues:
Total revenues	$ 6,665,000	$ 8,396,000	$ 25,458,000	$ 24,815,000

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 208,673	$ 205,577
Short-term investments	24,171	17,501
Trade accounts receivable	109,245	138,399
Income tax receivable	10,936	21,607
Inventories, net	81,918	56,719
Prepaid expenses and other receivables	27,915	29,366
Total current assets	462,858	469,169
Mineral interests, net	112,375	120,427
Property, plant and equipment, net	590,224	540,315
Non-current income tax receivable	10,561	21,310
Deferred income taxes	154,227	222,780
Other long-term assets	19,337	21,039
Total assets	1,349,582	1,395,040
Current liabilities:
Accounts payable	50,821	33,588
Accrued expenses	84,417	82,342
Short term financing lease liabilities	9,614
Other current liabilities	5,327	7,742
Current portion of long-term debt	0	760
Total current liabilities	150,179	124,432
Long-term debt	339,020	468,231
Asset retirement obligations	60,724	59,049
Long term financing lease liabilities	27,367
Other long-term liabilities	26,355	30,716
Total liabilities	603,645	682,428
Commitments and contingencies
Stockholders’ Equity:
Common stock, $0.01 par value per share (Authorized -140,000,000 shares as of September 30, 2019 and December 31, 2018, 53,293,449 issued and 51,071,608 outstanding as of September 30, 2019 and 53,256,098 issued and 51,622,898 outstanding as of December 31, 2018)	533	533
Preferred stock, $0.01 par value per share (10,000,000 shares authorized, no shares issued and outstanding)	0	0
Treasury stock, at cost (2,221,841 and 1,633,200 shares as of September 30, 2019 and December 31, 2018)	(50,576)	(38,030)
Additional paid in capital	242,458	239,827
Retained earnings	553,522	510,282
Total stockholders’ equity	745,937	712,612
Total liabilities and stockholders’ equity	$ 1,349,582	$ 1,395,040

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock shares authorized (in shares)	140,000,000	140,000,000
Common stock shares issued (in shares)	53,293,449	53,256,098
Common stock shares outstanding (in shares)	51,071,608	51,622,898
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock shares authorized (in shares)	10,000,000	10,000,000
Preferred stock shares issued (in shares)	0	0
Preferred stock shares outstanding (in shares)	0	0
Treasury stock (in shares)	2,221,841,000	1,633,200,000

CONDENSED STATEMENT OF CHANGES

CONDENSED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($)	Total	Common Stock	Preferred Stock	Treasury Stock	Additional Paid in Capital	Retained Earnings
Balance at beginning of period at Dec. 31, 2017		$ 534,000	$ 0	$ 0	$ 329,993,000	$ 82,496,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock purchase				(12,100,000)
Stock compensation					5,598,000
Dividends paid					(91,122,000)	(266,860,000)
Other					(5,442,000)	0
Net income	$ 322,597,000					322,597,000
Balance at end of period at Sep. 30, 2018	365,694,000	534,000	0	(12,100,000)	239,027,000	138,233,000
Balance at beginning of period at Jun. 30, 2018		534,000	0	(12,100,000)	238,162,000	88,274,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock purchase				0
Stock compensation					919,000
Dividends paid					0	(2,632,000)
Other					(54,000)	0
Net income	52,591,000					52,591,000
Balance at end of period at Sep. 30, 2018	365,694,000	534,000	0	(12,100,000)	239,027,000	138,233,000
Balance at beginning of period at Dec. 31, 2018	712,612,000	533,000	0	(38,030,000)	239,827,000	510,282,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock purchase				(12,546,000)
Stock compensation					3,875,000
Dividends paid					0	(237,814,000)
Other					(1,244,000)	105,000
Net income	280,949,000					280,949,000
Balance at end of period at Sep. 30, 2019	745,937,000	533,000	0	(50,576,000)	242,458,000	553,522,000
Balance at beginning of period at Jun. 30, 2019		533,000	0	(40,000,000)	241,020,000	511,105,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock purchase				(10,576,000)
Stock compensation					1,438,000
Dividends paid					0	(2,605,000)
Other					0	0
Net income	45,022,000					45,022,000
Balance at end of period at Sep. 30, 2019	$ 745,937,000	$ 533,000	$ 0	$ (50,576,000)	$ 242,458,000	$ 553,522,000

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
OPERATING ACTIVITIES
Net income	$ 280,949	$ 322,597
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and depletion	73,652	71,750
Deferred income tax expense	68,553	0
Stock based compensation expense	4,218	5,598
Amortization of debt issuance costs and debt discount/premium, net	1,024	2,057
Accretion of asset retirement obligations	2,436	3,465
Loss on early extinguishment of debt	9,756	0
Changes in operating assets and liabilities:
Trade accounts receivable	29,154	3,996
Income tax receivable	21,420	0
Inventories	(20,288)	(11,067)
Prepaid expenses and other receivables	7,080	4,484
Accounts payable	18,749	11,626
Accrued expenses and other current liabilities	645	19,185
Other	10,917	(5,092)
Net cash provided by operating activities	508,265	428,599
INVESTING ACTIVITIES
Purchase of property, plant and equipment	(78,366)	(79,579)
Deferred mine development costs	(18,398)	0
Proceeds from sale of property, plant and equipment	3,124	355
Sale of short-term investments	17,501	0
Purchases of short-term investments	(24,171)	0
Net cash used in investing activities	(100,310)	(79,224)
FINANCING ACTIVITIES
Dividends paid	(237,814)	(357,982)
Proceeds from issuance of debt	0	126,875
Retirements of debt, premium and fees	(140,272)	(2,295)
Principal repayments of capital lease obligations	(13,086)	0
Debt issuance costs paid	0	(3,713)
Common shares repurchased	(12,546)	(12,100)
Other	(1,139)	(5,442)
Net cash used in financing activities	(404,857)	(254,657)
Net increase in cash and cash equivalents and restricted cash	3,098	94,718
Cash and cash equivalents and restricted cash at beginning of period	206,405	36,264
Cash and cash equivalents and restricted cash at end of period	$ 209,503	$ 130,982

Business and Basis of Presentat

Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation Description of the Business Warrior Met Coal, Inc. (the "Company") is a U.S. based producer and exporter of met coal for a diversified customer base of blast furnace steel producers located primarily in Europe, South America and Asia. The Company also generates ancillary revenues from the sale of natural gas extracted as a byproduct from the underground coal mines and royalty revenues from leased properties. Basis of Presentation The accompanying financial statements are presented in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with 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 generally accepted accounting principles for complete financial statements. In our opinion, the financial statements include all adjustments (consisting of normal recurring accruals) necessary in order to make the financial statements not misleading. For further information, refer to the financial statements and related notes included in the Company's Annual Report on Form 10-K for the year ended December 31, 2018 (the "2018 Annual Report"). Operating results for the three and nine months ended September 30, 2019 are not necessarily indicative of the final results that may be expected for the year ended December 31, 2019 . The balance sheet at December 31, 2018 has been derived from the audited financial statements for the year ended December 31, 2018 included in the 2018 Annual Report.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Our significant accounting policies are consistent with those disclosed in Note 2 to our audited financial statements included in the 2018 Annual Report, except for changes related to new accounting pronouncements described in "New Accounting Pronouncements." Cash and Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the Condensed Balance Sheets that sum to the total of the same such amounts shown in the Condensed Statements of Cash Flows (in thousands): September 30, 2019 December 31, 2018 Cash and cash equivalents $ 208,673 $ 205,577 Restricted cash included in other long-term assets 830 828 Total cash and cash equivalents and restricted cash included in the Condensed Statements of Cash Flows $ 209,503 $ 206,405 Cash and cash equivalents include short-term deposits and highly liquid investments that have original maturities of three months or less when purchased and are stated at cost, which approximates fair value. As of September 30, 2019 and December 31, 2018 , restricted cash included in other long-term assets in the Condensed Balance Sheets represents amounts invested in certificates of deposits as financial assurance for post mining reclamation obligations. Short-Term Investments Instruments with maturities greater than three months, but less than twelve months, are included in short-term investments. The Company purchases United States Treasury ("Treasury") bills with maturities ranging from six to twelve months which are classified as held to maturity and are carried at amortized cost, which approximates fair value. The Company also purchases fixed income securities and certificates of deposits with varying maturities that are classified as available for sale and are carried at fair value. Securities classified as held to maturity are those securities that management has the intent and ability to hold to maturity. As of September 30, 2019 , short-term investments consisted of $24.2 million in cash and fixed income securities. As of December 31, 2018 , the Company’s short-term investments consisted of $17.5 million in Treasury bills with a maturity of six months . As of September 30, 2019 and December 31, 2018 , approximately $14.3 million and $17.5 million , respectively, of fixed income securities and Treasury bills were posted as collateral for the self-insured black lung related claims asserted by or on behalf of former employees of Walter Energy, Inc. ("Walter Energy") and its subsidiaries, which were assumed by the Company and relate to periods prior to March 31, 2016. Revenue Recognition Revenue is recognized when performance obligations under the terms of a contract with our customers are satisfied; for all contracts this occurs when control of the promised goods have been transferred to our customers. For coal shipments to domestic customers via rail, control is transferred when the railcar is loaded. For coal shipments to international customers via ocean vessel, control is transferred when the vessel is loaded at the Port of Mobile, Alabama. For natural gas sales, control is transferred when the gas has been transferred to the pipeline. Revenue is disaggregated between coal sales within the Company's mining segment and natural gas sales which is included in all other revenues, as disclosed in Note 14. Since February 2017, we have had an arrangement with XCoal Energy & Resource ("XCoal") to serve as XCoal's strategic partner for exports of low-volatility hard coking coal. Under this arrangement, XCoal takes title to and markets coal that we would historically have sold on the spot market, in an amount of the greater of (i) 10% of our total production during the applicable term of the arrangement or (ii) 250,000 metric tons. During the three months ended September 30, 2019 and 2018 , XCoal accounted for approximately $57.8 million , or 21% of total revenues, and $12.8 million , or 5% of total revenues, respectively. During the nine months ended September 30, 2019 and 2018 , XCoal accounted for approximately $220.8 million , or 21.0% of total revenues, and $157.8 million , or 16% of total revenues, respectively. New Accounting Pronouncements The Company adopted Accounting Standards Update ("ASU") No. 2016-02, "Leases (Topic 842)" as of January 1, 2019 using the modified retrospective approach (the "New Leases Standard"). The New Leases Standard requires a lessee to recognize a right-of-use asset and lease liability on its balance sheet for all leases. The Company has chosen to use its adoption date as its date of initial application. As a result, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. The Company made an accounting policy election that leases with an initial term of 12 months or less will remain off its balance sheet and lease payments will instead be recognized in the Condensed Statements of Operations on a straight-line basis over the lease term. Additionally, the Company elected the package of practical expedients for all leases, which permits the Company to forego reassessing expired or existing contracts to determine: whether they are or contain leases, lease classification, and initial direct costs. Management elected the optional transition expedient which allows the Company to continue applying the current policy for accounting for expired or existing land easement contracts that may have not been previously accounted for under ASC Leases (Topic 840). New or modified land easements executed after adoption will be considered under the New Leases Standard. The Company elected the practical expedient as an accounting policy election for all asset classifications, which allows it to account for them as a single lease component, rather than as separate lease and non-lease components. As the Company’s historical operating leases are primarily short-term rental agreements of less than one year, the Company did not record any additional lease assets or lease liabilities upon adoption of the New Leases Standard. Therefore, the New Leases Standard did not impact the Company's balance sheet or consolidated net income and had no impact on cash flows upon adoption. As of September 30, 2019 , the Company has a right-of-use asset of $41.2 million , net of accumulated amortization, a short-term financing lease liability of $9.6 million and a long-term financing lease liability of $27.4 million . On August 17, 2018, the SEC adopted a final rule that eliminates or amends certain disclosure requirements that were deemed redundant and outdated in light of changes in SEC requirements, U.S. GAAP or changes in technology or the business environment. The rule also requires registrants to include in their interim financial statements a reconciliation of changes in stockholders’ equity in the notes or as a separate statement. The analysis should reconcile the beginning balance to the ending balance of each caption in shareholders’ equity for each period for which an income statement is required to be filed. The final rule became effective November 5, 2018. The Company has provided a reconciliation for the three and nine months ended September 30, 2019 and 2018 in this Form 10-Q. The eliminated or amended disclosures did not have a material impact on the Company’s unaudited condensed financial statements.

Inventories, net

Inventories, net	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Inventories, net	Inventories, net Inventories, net are summarized as follows (in thousands): September 30, 2019 December 31, 2018 Coal $ 55,561 $ 32,854 Raw materials, parts, supplies and other, net 26,357 23,865 Total inventories, net $ 81,918 $ 56,719

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the three and nine months ended September 30, 2019 , the Company estimated its annual effective tax rate and applied this effective tax rate to its year-to-date pretax income at the end of the interim reporting period. The tax effect of unusual or infrequently occurring items, including effects of changes in tax laws or rates and changes in judgment about the realizability of deferred tax assets, are reported in the interim period in which they occur. For the three and nine months ended September 30, 2019 , the Company had income tax expense of $7.6 million and $68.6 million , respectively. The income tax expense represents a noncash expense as the Company continues to utilize its NOLs. The Company had no income tax expense for the three and nine months ended September 30, 2018 , due to the utilization of NOLs to offset taxable income for which a full valuation allowance was recorded. As a result of various favorable factors further discussed in the 2018 Annual Report, the Company released its valuation allowance against its net deferred income tax assets in the fourth quarter of 2018.

Debt

Debt	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt Debt consisted of the following (in thousands): September 30, 2019 December 31, 2018 Weighted Average Interest Rate at September 30, 2019 Final Maturity Senior Secured Notes $ 343,435 $ 475,000 8% 2024 Promissory note — 760 Debt discount/premium, net (4,415 ) (6,769 ) Total debt 339,020 468,991 Less: current debt — (760 ) Total long-term debt $ 339,020 $ 468,231 Senior Secured Notes On November 2, 2017, the Company issued $350.0 million aggregate principal amount of its 8.00% Senior Secured Notes due 2024 (the "Original Notes"). It then issued an additional $125.0 million in aggregate principal amount of its 8.00% Senior Secured Notes due 2024 (the “New Notes” and, together with the Original Notes, the "Notes") on March 1, 2018. The New Notes were issued as "Additional Notes" under the indenture dated as of November 2, 2017 (the "Original Indenture"), among the Company, the subsidiary guarantors party thereto and Wilmington Trust, National Association, as trustee and priority lien collateral trustee, as supplemented by the First Supplemental Indenture, dated as of March 1, 2018 (the "First Supplemental Indenture" and, the Original Indenture as supplemented thereby and by the Second Supplemental Indenture, dated as of March 2, 2018, the "Indenture"). The Notes mature on November 1, 2024 and interest is payable on May 1 and November 1 of each year. In connection with the issuance of the New Notes, the Company incurred transaction costs of approximately $0.5 million and $4.5 million for the three and nine months ended September 30, 2018 , respectively, which consists of legal fees and structuring fees, and is included in transaction and other expenses in the Condensed Statements of Operations. Offers to Purchase the Notes On February 21, 2019, the Company commenced an offer to purchase (the “Restricted Payment Offer”), in cash, up to $150,000,000 principal amount of its outstanding Notes, at a repurchase price of 103% of the aggregate principal amount of such Notes, plus accrued and unpaid interest with respect to such Notes to, but not including, the date of repurchase (the “Restricted Payment Repurchase Price”). Concurrently with, but separate from, the Restricted Payment Offer, the Company commenced a cash tender offer (the “Tender Offer” and, together with the Restricted Payment Offer, the “Offers”) to purchase up to $150,000,000 principal amount of the Notes at a repurchase price of 104.25% of the aggregate principal amount of such Notes, plus accrued and unpaid interest to, but not including, the date of repurchase (the “TO Repurchase Price”). The Offers expired on March 22, 2019 (the “Expiration Date”). Restricted Payment Offer As of the Expiration Date, $1,900,000 aggregate principal amount of the Notes were validly tendered and not validly withdrawn pursuant to the Restricted Payment Offer. Pursuant to the terms of the Restricted Payment Offer: (1) an automatic pro ration factor of 31.5789% was applied to the $1,900,000 aggregate principal amount of the Notes that were validly tendered and not validly withdrawn in the Restricted Payment Offer (rounded down to avoid the purchase of Notes in a principal amount other than in integrals of $1,000 ), which resulted in $599,000 aggregate principal amount of the Notes (the “RP Pro-Rated Tendered Notes”); (2) the Company accepted all $599,000 aggregate principal amount of the RP Pro-Rated Tendered Notes for payment of the Restricted Payment Repurchase Price in cash; and (3) the remaining balance of $1,301,000 aggregate principal amount of the Notes tendered that were not RP Pro-Rated Tendered Notes were not accepted for payment and were returned to the tendering holder of the Notes. The Company consummated the Restricted Payment Offer on March 25, 2019. Accordingly, pursuant to the terms of the Indenture, the Company was permitted to make one or more restricted payments in the form of special dividends to holders of the Company’s common stock and/or repurchases of the Company’s common stock in the aggregate amount of up to $299,401,000 (the "RP Basket") without having to make another offer to repurchase Notes. The Company used a portion of the RP Basket to pay the April 2019 Special Dividend (as defined below) and intends to use the remainder of the RP Basket to make repurchases under the New Stock Repurchase Program (as defined below). Tender Offer As of the Expiration Date, $415,099,000 aggregate principal amount of the Notes were validly tendered and not validly withdrawn pursuant to the Tender Offer. Pursuant to the terms of the Tender Offer: (1) an automatic pro ration factor of 31.5789% was applied to the $415,099,000 aggregate principal amount of the Notes that were validly tendered and not validly withdrawn in the Tender Offer (rounded down to avoid the purchase of Notes in a principal amount other than in integrals of $1,000 ), which resulted in $130,966,000 aggregate principal amount of the Notes (the “TO Pro-Rated Tendered Notes”); (2) the Company accepted all $130,966,000 aggregate principal amount of the TO Pro-Rated Tendered Notes for payment of the TO Repurchase Price in cash; and (3) the remaining balance of $284,133,000 aggregate principal amount of the Notes tendered that were not TO Pro-Rated Tendered Notes were not accepted for payment and were returned to the tendering holder of the Notes. The Company consummated the Tender Offer on March 26, 2019. In connection with the payments for the RP Pro-Rated Tendered Notes and the TO Pro-Rated Tendered Notes, the Company recognized a loss on early extinguishment of debt of $9.8 million during the nine months ended September 30, 2019 .

Other Long-Term Liabilities

Other Long-Term Liabilities	9 Months Ended
	Sep. 30, 2019
Other Liabilities Disclosure [Abstract]
Other Long-Term Liabilities	Other Long-Term Liabilities Other long-term liabilities are summarized as follows (in thousands): September 30, 2019 December 31, 2018 Black lung obligations $ 25,413 $ 25,206 Other 942 5,510 Total other long-term liabilities $ 26,355 $ 30,716

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases The Company primarily enters into rental agreements for certain mining equipment that are for periods of 12 months or less, some of which include options to extend the leases. Leases that are for periods of 12 months or less are not recorded on the balance sheet in accordance with the Company's accounting policy election described in Note 2. The Company recognizes lease expense on these agreements on a straight-line basis over the lease term. Additionally, the Company has certain finance leases for mining equipment that expire over various contractual periods. The leases have remaining lease terms of one to five years . These leases do not include an option to renew. Amortization expense for finance leases is included in depreciation and depletion expense. Supplemental balance sheet information related to leases was as follows (in thousands): September 30, 2019 Finance lease right-of-use assets, net (1) $ 41,165 Finance lease liabilities Current 9,614 Noncurrent 27,367 Total finance lease liabilities $ 36,981 Weighted average remaining lease term - finance leases (in months) 47.4 Weighted average discount rate - finance leases (2) 6.00 % (1) Finance lease right-of-use assets are recorded net of accumulated amortization of $4.8 million and are included in property, plant and equipment, net in the Condensed Balance Sheets as of September 30, 2019 . (2) When an implicit discount rate is not readily available in a lease, the Company uses its incremental borrowing rate based on information available at the commencement date when determining the present value of lease payments. The components of lease expense were as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Operating lease cost (1): $ 688 $ 1,866 Finance lease cost: Amortization of leased assets 2,120 7,950 Interest on lease liabilities 786 1,194 Net lease cost $ 3,594 $ 11,010 (1) Includes leases that are for periods of 12 months or less. Maturities of lease liabilities were as follows (in thousands): Finance Leases (1) 2019 $ 2,969 2020 10,752 2021 8,558 2022 8,558 2023 8,558 Thereafter 842 Total 40,237 Less: amount representing interest (5,556 ) Present value of lease liabilities $ 34,681 (1) Finance lease payments exclude $2.3 million of future payments required under signed lease agreements that have not yet commenced. Supplemental cash flow information related to leases was as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 786 $ 1,194 Financing cash flows from finance leases $ 5,432 $ 13,086 Non-cash right-of-use assets obtained in exchange for lease obligations: Finance leases $ 1,812 $ 42,114 As of September 30, 2019 , the Company had additional commitments for finance leases, primarily for mining equipment, that have not yet commenced of $2.3 million . These finance leases will commence between fiscal year 2019 and 2021 with lease terms of one to two years .
Leases	Leases The Company primarily enters into rental agreements for certain mining equipment that are for periods of 12 months or less, some of which include options to extend the leases. Leases that are for periods of 12 months or less are not recorded on the balance sheet in accordance with the Company's accounting policy election described in Note 2. The Company recognizes lease expense on these agreements on a straight-line basis over the lease term. Additionally, the Company has certain finance leases for mining equipment that expire over various contractual periods. The leases have remaining lease terms of one to five years . These leases do not include an option to renew. Amortization expense for finance leases is included in depreciation and depletion expense. Supplemental balance sheet information related to leases was as follows (in thousands): September 30, 2019 Finance lease right-of-use assets, net (1) $ 41,165 Finance lease liabilities Current 9,614 Noncurrent 27,367 Total finance lease liabilities $ 36,981 Weighted average remaining lease term - finance leases (in months) 47.4 Weighted average discount rate - finance leases (2) 6.00 % (1) Finance lease right-of-use assets are recorded net of accumulated amortization of $4.8 million and are included in property, plant and equipment, net in the Condensed Balance Sheets as of September 30, 2019 . (2) When an implicit discount rate is not readily available in a lease, the Company uses its incremental borrowing rate based on information available at the commencement date when determining the present value of lease payments. The components of lease expense were as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Operating lease cost (1): $ 688 $ 1,866 Finance lease cost: Amortization of leased assets 2,120 7,950 Interest on lease liabilities 786 1,194 Net lease cost $ 3,594 $ 11,010 (1) Includes leases that are for periods of 12 months or less. Maturities of lease liabilities were as follows (in thousands): Finance Leases (1) 2019 $ 2,969 2020 10,752 2021 8,558 2022 8,558 2023 8,558 Thereafter 842 Total 40,237 Less: amount representing interest (5,556 ) Present value of lease liabilities $ 34,681 (1) Finance lease payments exclude $2.3 million of future payments required under signed lease agreements that have not yet commenced. Supplemental cash flow information related to leases was as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 786 $ 1,194 Financing cash flows from finance leases $ 5,432 $ 13,086 Non-cash right-of-use assets obtained in exchange for lease obligations: Finance leases $ 1,812 $ 42,114 As of September 30, 2019 , the Company had additional commitments for finance leases, primarily for mining equipment, that have not yet commenced of $2.3 million . These finance leases will commence between fiscal year 2019 and 2021 with lease terms of one to two years .

Net Income per Share

Net Income per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Income per Share	Net Income per Share Basic and diluted net income per share was calculated as follows (in thousands, except per share data): For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Numerator: Net income $ 45,022 $ 52,591 $ 280,949 $ 322,597 Denominator: Weighted-average shares used to compute net income per share—basic 51,348 52,707 51,469 52,916 Dilutive restrictive stock awards 134 1 130 29 Weighted-average shares used to compute net income per share—diluted 51,482 52,708 51,599 52,945 Net income per share—basic and diluted $ 0.88 $ 1.00 $ 5.46 $ 6.10 Net income per share—diluted $ 0.87 $ 1.00 $ 5.44 $ 6.09 2017 Equity Plan On February 8, 2019, the Company awarded 306,314 restricted stock unit awards under the Company's 2017 Equity Incentive Plan (the "2017 Equity Plan"). These awards have certain service-based, performance-based and market-based vesting conditions, as applicable. The service-based awards vest over a period of three years and the performance-based and market-based awards are based on the Company's performance in each of the three years . The Company recognized approximately $0.9 million and $2.2 million in stock compensation expense associated with these awards for the three and nine months ended September 30, 2019 , respectively. Additionally, the Company awarded $1.5 million of restricted stock unit awards under the 2017 Equity Plan that can be settled in shares or in cash at the election of employees. These awards have certain service-based and performance-based vesting conditions and can be earned no later than December 31, 2021. If the Company were to settle these awards in shares these awards would represent 76,844 shares based on the Company's closing share price on September 30, 2019 . The Company recognized approximately $129 thousand and $343 thousand in stock compensation expense associated with these awards for the three and nine months ended September 30, 2019 , respectively. As of September 30, 2019 , there were 161,998 restricted stock unit awards for which the service-based vesting conditions for these awards were not met as of the measurement date. As such, these awards were excluded from basic earnings per share. These awards had a 39,983 and 34,922 share impact on dilutive weighted average shares for the three and nine months ended September 30, 2019 , respectively. As of September 30, 2019 , there were 271,589 restricted stock unit awards for which the performance-based and market-based vesting conditions were not met as of the measurement date and, as such, these awards were excluded from basic and diluted earnings per share. For the 76,844 restricted stock unit awards classified as a liability, the Company considered the impact on diluted earnings as if the award was settled in cash or in shares. These awards had a 22,243 and 25,617 share impact on dilutive weighted average shares for the three and nine months ended September 30, 2019 . As of September 30, 2019 , there were 43,580 shares of our common stock contingently issuable upon the settlement of a vested phantom unit award granted under our 2016 Equity Plan (as defined below) and 13,157 shares of our common stock contingently issuable upon the settlement of a vested restricted stock unit award under our 2017 Equity Plan. The settlement date for these awards is the earlier of a change in control as described in our 2016 Equity Plan or 2017 Equity Plan, as applicable, or five years from the grant date. These awards are vested and, as such, have been included in the weighted average shares used to compute basic and diluted net income per share. 2016 Equity Plan As of September 30, 2019 , there were 98,216 restricted stock unit awards granted under the Company's 2016 Equity Incentive Plan (the "2016 Equity Plan") to certain directors and employees, for which the service-based vesting conditions for these awards were not met as of the measurement date. As such, these awards were excluded from basic earnings per share. These awards had a 72,366 and 69,484 share impact on dilutive weighted average shares for the three and nine months ended September 30, 2019 , respectively.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company owns a 50% interest in Black Warrior Methane (“BWM”) and Black Warrior Transmission (“BWT”), which are accounted for under the proportionate consolidation method and equity method, respectively. The Company has granted the rights to produce and sell methane gas from its coal mines to BWM and BWT. The Company’s net investments in, advances to/from and equity in earnings or loss of BWT are not material to the Company. The Company supplied labor to BWM and incurred costs, including property and liability insurance, to support the joint venture. The Company charged the joint venture for such costs on a monthly basis, which totaled $0.6 million and $1.1 million , respectively, for the three and nine months ended September 30, 2019 and $0.8 million and $2.3 million , respectively, for the three and nine months ended September 30, 2018 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Environmental Matters The Company is subject to a wide variety of laws and regulations concerning the protection of the environment, both with respect to the construction and operation of its plants, mines and other facilities and with respect to remediating environmental conditions that may exist at its own and other properties. The Company believes it is in compliance with federal, state and local environmental laws and regulations. The Company accrues for environmental expenses resulting from existing conditions that relate to past operations when the costs are probable and can be reasonably estimated. As of September 30, 2019 and December 31, 2018 , there were no accruals for environmental matters other than asset retirement obligations for mine reclamation. Miscellaneous Litigation From time to time, the Company is party to lawsuits arising in the ordinary course of their businesses. The Company records costs relating to these matters when a loss is probable and the amount can be reasonably estimated. The effect of the outcome of these matters on the Company’s future results of operations cannot be predicted with certainty as any such effect depends on future results of operations and the amount and timing of the resolution of such matters. As of September 30, 2019 and December 31, 2018 , there were no items accrued for miscellaneous litigation. Walter Canada Settlement Proceeds On July 15, 2015, Walter Energy and certain of its wholly owned U.S. subsidiaries, including Jim Walter Resources, Inc. (“JWR”) filed voluntary petitions for relief under Chapter 11 of Title 11 of the U.S. Bankruptcy Code (the “Chapter 11 Cases”) in the Northern District of Alabama, Southern Division. On December 7, 2015, Walter Energy Canada Holdings, Inc., Walter Canadian Coal Partnership and their Canadian affiliates (collectively “Walter Canada”) applied for and were granted protection under the Companies’ Creditors Arrangement Act (the “CCAA”) pursuant to an Initial Order of the Supreme Court of British Columbia. In connection with the Company’s acquisition of certain core operating assets of Walter Energy, the Company acquired a receivable owed to Walter Energy by Walter Canada for certain shared services provided by Walter Energy to Walter Canada (the “Shared Services Claim”) and a receivable for unpaid interest owed to Walter Energy from Walter Canada in respect of a promissory note (the “Hybrid Debt Claim”). Each of these claims were asserted by the Company in the Walter Canada CCAA proceedings. Walter Energy deemed these receivables to be impaired for the year ended December 31, 2015 and the Company did not assign any value to these receivables in acquisition accounting as collectability was deemed remote. In May and August 2019, the Company received approximately $17.5 million and $5.3 million , respectively, in settlement proceeds for the Shared Services Claim and Hybrid Debt Claim which is reflected as other income in the Condensed Statement of Operations. The Company has received $22.8 million in settlement proceeds for the Shared Services Claim and Hybrid Debt Claim year to date which is reflected as other income in the Condensed Statement of Operations. The collectability of additional amounts, if any, related to the Shared Services Claim and Hybrid Debt Claim depends on the outcome of, and the timing of any resolutions of, the Walter Canada CCAA proceedings and cannot be predicted with certainty. Commitments and Contingencies—Other The Company is party to various transportation and throughput agreements with rail and barge transportation providers and the Alabama State Port Authority. These agreements contain annual minimum tonnage guarantees with respect to coal transported from the mine sites to the Port of Mobile, Alabama, the unloading of rail cars or barges, and the loading of vessels. If the Company does not meet its minimum throughput obligations, which are based on annual minimum amounts, it is required to pay the transportation providers or the Alabama State Port Authority a contractually specified amount per metric ton for the difference between the actual throughput and the minimum throughput requirement. At September 30, 2019 and December 31, 2018 , the Company had no liability recorded for minimum throughput requirements. Royalty Obligations A substantial amount of the coal that the Company mines is produced from mineral reserves leased from third-party land owners. These leases convey mining rights to the Company in exchange for royalties to be paid to the land owner as either a fixed amount per ton or as a percentage of the sales price. Although coal leases have varying renewal terms and conditions, they generally last for the economic life of the reserves. Coal royalty expense was $19.7 million and $75.7 million for the three and nine months ended September 30, 2019 , respectively, and $19.9 million and $74.1 million for the three and nine months ended September 30, 2018

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Pursuant to the Company's certificate of incorporation, the Company is authorized to issue up to 140,000,000 shares of common stock $0.01 , par value per share and 10,000,000 shares of preferred stock $0.01 par value per share. New Stock Repurchase Program On March 26, 2019, the Company's board of directors (the "Board") approved the Company's second stock repurchase program (the “New Stock Repurchase Program”) that authorizes repurchases of up to an aggregate of $70.0 million of the Company's outstanding common stock. The Company fully exhausted its previous stock repurchase program (the "First Stock Repurchase Program") of $40.0 million of its outstanding common stock. The New Stock Repurchase Program does not require the Company to repurchase a specific number of shares or have an expiration date. The New Stock Repurchase Program may be suspended or discontinued by the Board at any time without prior notice. Under the New Stock Repurchase Program, the Company may repurchase shares of its common stock from time to time, in amounts, at prices and at such times as the Company deems appropriate, subject to market and industry conditions, share price, regulatory requirements as determined from time to time by the Company and other considerations. The Company’s repurchases may be executed using open market purchases or privately negotiated transactions in accordance with applicable securities laws and regulations, including Rule 10b-18 of the Exchange Act and repurchases may be executed pursuant to Rule 10b5-1 under the Exchange Act. Repurchases will be subject to limitations in the ABL Facility and the Indenture. The Company intends to fund repurchases under the New Stock Repurchase Program from cash on hand and/or other sources of liquidity. As of September 30, 2019 , the Company has repurchased 500,000 shares for approximately $10.6 million , leaving approximately $58.8 million of share repurchases authorized under the New Stock Repurchase Program. Secondary Equity Offerings On May 10, 2018 certain stockholders of the Company sold 8,000,000 shares of the Company's common stock in a public secondary offering at a price to the underwriter of $24.20 per share. The Company did not receive any of the proceeds from this offering. In connection with this offering, the Company repurchased 500,000 shares of common stock under the Stock Repurchase Program, funded with cash on hand for an aggregate amount of $12.1 million (the "Stock Repurchase"). The shares repurchased by the Company in the Stock Repurchase are reflected as Treasury Stock on the Condensed Balance Sheets. On June 14, 2018, certain stockholders of the Company sold 5,000,000 shares of the Company's common stock in a public secondary offering at a price to the underwriter of $28.35 per share. The Company did not receive any of the proceeds from the offering. On August 8, 2018, certain stockholders of the Company sold 2,204,806 shares of the Company's common stock in a public secondary offering (the "August 2018 Equity Offering") at a price to the underwriter of $25.40 per share. The Company did not receive any of the proceeds from the offering. We refer to these offerings herein collectively as the "Secondary Equity Offerings." In connection with the Secondary Equity Offerings, we incurred transaction costs of approximately $2.8 million and $3.0 million for the three and nine months ended September 30, 2018, respectively. Regular Quarterly Dividend On February 19, 2019, the Board declared a regular quarterly cash dividend of $0.05 per share, totaling $2.6 million , which was paid on March 11, 2019, to stockholders of record as of the close of business on March 4, 2019. On April 23, 2019, the Board declared a regular quarterly cash dividend of $0.05 per share, totaling approximately $2.6 million , which was paid on May 10, 2019 to stockholders of record as of the close of business on May 3, 2019. On July 23, 2019, the Board declared a regular quarterly cash dividend of $0.05 per share, totaling approximately $2.6 million , which was paid on August 9, 2019 to stockholders of record as of the close of business on August 2, 2019. April 2019 Special Dividend On April 23, 2019, the Board declared a special cash dividend of approximately $230.0 million (the "April 2019 Special Dividend"), which was paid on May 14, 2019 to stockholders of record as of the close of business on May 6, 2019. The Company funded the April 2019 Special Dividend with cash on hand.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The Company enters into natural gas swap contracts from time to time to hedge the exposure to variability in expected future cash flows associated with the fluctuations in the price of natural gas related to the Company’s forecasted sales. As of September 30, 2019 , the Company had no natural gas swap contracts outstanding. As of December 31, 2018 , the Company had natural gas swap contracts outstanding with notional amounts totaling 2,100 million British thermal units that matured in the first quarter of 2019. The Company’s natural gas swap contracts economically hedge certain risk but are not designated as hedges for financial reporting purposes. All changes in the fair value of these derivative instruments are recorded as other revenues in the Condensed Statements of Operations. The Company records all derivative instruments at fair value and had no liability as of September 30, 2019 and a liability of $0.2 million as of December 31, 2018 included in other current liabilities in the accompanying Condensed Balance Sheets.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company had no assets or any other liabilities measured at fair value on a recurring basis as of September 30, 2019 . The following table presents information about the Company’s financial liabilities measured at fair value on a recurring basis as of December 31, 2018 and indicates the level of the fair value hierarchy utilized to determine such fair value (in thousands): Fair Value Measurements as of December 31, 2018 Using: Level 1 Level 2 Level 3 Total Liabilities: Natural gas swap contracts $ — $ 178 $ — $ 178 The following methods and assumptions were used to estimate the fair value for which the fair value option was not elected: Cash and cash equivalents, short-term investments, restricted cash, receivables and trade accounts payable— The carrying amounts reported in the Condensed Balance Sheets approximate fair value due to the short-term nature of these assets and liabilities. Debt— The Company's outstanding debt is carried at cost. As of September 30, 2019 , there were no borrowings outstanding under the ABL Facility, with $116.1 million available, net of outstanding letters of credit of $8.9 million . There were no borrowings outstanding under the ABL Facility and there were $4.6 million of letters of credit issued and outstanding under the ABL Facility as of December 31, 2018 . As of September 30, 2019 , the estimated fair value of the Notes is approximately $357.2 million

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Segment Information	Segment Information The Company identifies a business as an operating segment if: (i) it engages in business activities from which it may earn revenues and incur expenses; (ii) its operating results are regularly reviewed by the Chief Operating Decision Maker (“CODM”), who is the Company’s Chief Executive Officer, to make decisions about resources to be allocated to the segment and assess its performance; and (iii) it has available discrete financial information. The Company has determined that its two underground mining operations are its operating segments. The CODM reviews financial information at the operating segment level to allocate resources and to assess the operating results and financial performance for each operating segment. Operating segments are aggregated into a reportable segment if the operating segments have similar quantitative economic characteristics and if the operating segments are similar in the following qualitative characteristics: (i) nature of products and services; (ii) nature of production processes; (iii) type or class of customer for their products and services; (iv) methods used to distribute the products or provide services; and (v) if applicable, the nature of the regulatory environment. The Company has determined that the two operating segments are similar in both quantitative and qualitative characteristics and thus the two operating segments have been aggregated into one reportable segment. The Company has determined that its natural gas and royalty businesses did not meet the criteria in ASC 280 to be considered as operating or reportable segments. Therefore, the Company has included their results in an “all other” category as a reconciling item to consolidated amounts. The Company does not allocate all of its assets, or its depreciation and depletion expense, selling, general and administrative expenses, transactions costs, interest expense, and income tax expense by segment. The following tables include reconciliations of segment information to consolidated amounts (in thousands): For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Revenues Mining $ 280,841 $ 264,908 $ 1,037,950 $ 992,832 All other 6,665 8,396 25,458 24,815 Total revenues $ 287,506 $ 273,304 $ 1,063,408 $ 1,017,647 For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Capital Expenditures Mining 23,494 $ 22,924 $ 73,583 $ 76,422 All other 2,772 1,236 4,783 3,157 Total capital expenditures 26,266 $ 24,160 $ 78,366 $ 79,579 The Company evaluates the performance of its segment based on Segment Adjusted EBITDA, which is defined as net income adjusted for other revenues, cost of other revenues, depreciation and depletion, selling, general and administrative, net interest expense, income tax expense, loss on early extinguishment of debt, other income and certain transactions or adjustments that the CODM does not consider for the purposes of making decisions to allocate resources among segments or assessing segment performance. Segment Adjusted EBITDA does not represent and should not be considered as an alternative to cost of sales under GAAP and may not be comparable to other similarly titled measures used by other companies. Below is a reconciliation of Segment Adjusted EBITDA to net income, which is its most directly comparable financial measure calculated and presented in accordance with GAAP (in thousands): For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Segment Adjusted EBITDA $ 90,620 $ 97,720 $ 459,912 $ 456,425 Other revenues 6,665 8,396 25,458 24,815 Cost of other revenues (7,583 ) (6,704 ) (23,346 ) (21,826 ) Depreciation and depletion (25,741 ) (26,071 ) (73,652 ) (71,750 ) Selling, general and administrative (9,362 ) (7,357 ) (29,050 ) (29,056 ) Transaction and other expenses — (3,265 ) — (7,539 ) Loss on early extinguishment of debt — — (9,756 ) — Other income 5,272 — 22,815 — Interest expense, net (7,250 ) (10,128 ) (22,793 ) (28,472 ) Income tax expense (7,599 ) — (68,639 ) — Net income $ 45,022 $ 52,591 $ 280,949 $ 322,597

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Regular Quarterly Dividend On October 18, 2019, the Board declared a regular quarterly cash dividend of $0.05 per share, totaling approximately $2.6 million , which will be paid on November 4, 2019 to stockholders of record as of the close of business on October 28, 2019. Shelf Registration Statement On October 29, 2019, the Company filed a universal shelf registration statement on Form S-3 (the “Shelf Registration Statement”) with the SEC, which became effective automatically. The Company does not have any commitments or plans to sell any securities under the Shelf Registration Statement at this time. The Shelf Registration Statement allows for primary offerings from time to time of the Company’s debt securities, common stock, preferred stock, rights, depositary shares, warrants and stock purchase contracts and secondary offerings from time to time of the Company’s common stock. The type of securities and the specific terms thereof will be determined at the time of the applicable offering (if any) and will be described in the applicable prospectus supplement to be filed separately with the SEC.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	The accompanying financial statements are presented in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and with 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 generally accepted accounting principles for complete financial statements. In our opinion, the financial statements include all adjustments (consisting of normal recurring accruals) necessary in order to make the financial statements not misleading.
Cash and Cash Equivalents and Restricted Cash	Cash and cash equivalents include short-term deposits and highly liquid investments that have original maturities of three months or less when purchased and are stated at cost, which approximates fair value. As of September 30, 2019 and December 31, 2018 , restricted cash included in other long-term assets in the Condensed Balance Sheets represents amounts invested in certificates of deposits as financial assurance for post mining reclamation obligations.
Short-Term Investments	Short-Term Investments Instruments with maturities greater than three months, but less than twelve months, are included in short-term investments. The Company purchases United States Treasury ("Treasury") bills with maturities ranging from six to twelve months which are classified as held to maturity and are carried at amortized cost, which approximates fair value. The Company also purchases fixed income securities and certificates of deposits with varying maturities that are classified as available for sale and are carried at fair value. Securities classified as held to maturity are those securities that management has the intent and ability to hold to maturity.
Revenue Recognition	Revenue Recognition
New Accounting Pronouncements	New Accounting Pronouncements The Company adopted Accounting Standards Update ("ASU") No. 2016-02, "Leases (Topic 842)" as of January 1, 2019 using the modified retrospective approach (the "New Leases Standard"). The New Leases Standard requires a lessee to recognize a right-of-use asset and lease liability on its balance sheet for all leases. The Company has chosen to use its adoption date as its date of initial application. As a result, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. The Company made an accounting policy election that leases with an initial term of 12 months or less will remain off its balance sheet and lease payments will instead be recognized in the Condensed Statements of Operations on a straight-line basis over the lease term. Additionally, the Company elected the package of practical expedients for all leases, which permits the Company to forego reassessing expired or existing contracts to determine: whether they are or contain leases, lease classification, and initial direct costs. Management elected the optional transition expedient which allows the Company to continue applying the current policy for accounting for expired or existing land easement contracts that may have not been previously accounted for under ASC Leases (Topic 840). New or modified land easements executed after adoption will be considered under the New Leases Standard. The Company elected the practical expedient as an accounting policy election for all asset classifications, which allows it to account for them as a single lease component, rather than as separate lease and non-lease components. As the Company’s historical operating leases are primarily short-term rental agreements of less than one year, the Company did not record any additional lease assets or lease liabilities upon adoption of the New Leases Standard. Therefore, the New Leases Standard did not impact the Company's balance sheet or consolidated net income and had no impact on cash flows upon adoption. As of September 30, 2019 , the Company has a right-of-use asset of $41.2 million , net of accumulated amortization, a short-term financing lease liability of $9.6 million and a long-term financing lease liability of $27.4 million . On August 17, 2018, the SEC adopted a final rule that eliminates or amends certain disclosure requirements that were deemed redundant and outdated in light of changes in SEC requirements, U.S. GAAP or changes in technology or the business environment. The rule also requires registrants to include in their interim financial statements a reconciliation of changes in stockholders’ equity in the notes or as a separate statement. The analysis should reconcile the beginning balance to the ending balance of each caption in shareholders’ equity for each period for which an income statement is required to be filed. The final rule became effective November 5, 2018. The Company has provided a reconciliation for the three and nine months ended September 30, 2019 and 2018 in this Form 10-Q. The eliminated or amended disclosures did not have a material impact on the Company’s unaudited condensed financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the Condensed Balance Sheets that sum to the total of the same such amounts shown in the Condensed Statements of Cash Flows (in thousands): September 30, 2019 December 31, 2018 Cash and cash equivalents $ 208,673 $ 205,577 Restricted cash included in other long-term assets 830 828 Total cash and cash equivalents and restricted cash included in the Condensed Statements of Cash Flows $ 209,503 $ 206,405
Schedule of Restricted Cash and Cash Equivalents	The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the Condensed Balance Sheets that sum to the total of the same such amounts shown in the Condensed Statements of Cash Flows (in thousands): September 30, 2019 December 31, 2018 Cash and cash equivalents $ 208,673 $ 205,577 Restricted cash included in other long-term assets 830 828 Total cash and cash equivalents and restricted cash included in the Condensed Statements of Cash Flows $ 209,503 $ 206,405

Inventories, net (Tables)

Inventories, net (Tables)	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Schedule of Inventories, Net	Inventories, net are summarized as follows (in thousands): September 30, 2019 December 31, 2018 Coal $ 55,561 $ 32,854 Raw materials, parts, supplies and other, net 26,357 23,865 Total inventories, net $ 81,918 $ 56,719

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Debt consisted of the following (in thousands): September 30, 2019 December 31, 2018 Weighted Average Interest Rate at September 30, 2019 Final Maturity Senior Secured Notes $ 343,435 $ 475,000 8% 2024 Promissory note — 760 Debt discount/premium, net (4,415 ) (6,769 ) Total debt 339,020 468,991 Less: current debt — (760 ) Total long-term debt $ 339,020 $ 468,231

Other Long-Term Liabilities (Ta

Other Long-Term Liabilities (Tables)	9 Months Ended
	Sep. 30, 2019
Other Liabilities Disclosure [Abstract]
Other Long-Term Liabilities	Other long-term liabilities are summarized as follows (in thousands): September 30, 2019 December 31, 2018 Black lung obligations $ 25,413 $ 25,206 Other 942 5,510 Total other long-term liabilities $ 26,355 $ 30,716

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Supplemental Balance Sheet Information	Supplemental balance sheet information related to leases was as follows (in thousands): September 30, 2019 Finance lease right-of-use assets, net (1) $ 41,165 Finance lease liabilities Current 9,614 Noncurrent 27,367 Total finance lease liabilities $ 36,981 Weighted average remaining lease term - finance leases (in months) 47.4 Weighted average discount rate - finance leases (2) 6.00 % (1) Finance lease right-of-use assets are recorded net of accumulated amortization of $4.8 million and are included in property, plant and equipment, net in the Condensed Balance Sheets as of September 30, 2019 . (2) When an implicit discount rate is not readily available in a lease, the Company uses its incremental borrowing rate based on information available at the commencement date when determining the present value of lease payments.
Direct Financing Lease, Lease Expense	The components of lease expense were as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Operating lease cost (1): $ 688 $ 1,866 Finance lease cost: Amortization of leased assets 2,120 7,950 Interest on lease liabilities 786 1,194 Net lease cost $ 3,594 $ 11,010 (1) Includes leases that are for periods of 12 months or less.
Operating Lease, Lease Expense	The components of lease expense were as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Operating lease cost (1): $ 688 $ 1,866 Finance lease cost: Amortization of leased assets 2,120 7,950 Interest on lease liabilities 786 1,194 Net lease cost $ 3,594 $ 11,010 (1) Includes leases that are for periods of 12 months or less.
Finance Lease, Liability, Maturity	Maturities of lease liabilities were as follows (in thousands): Finance Leases (1) 2019 $ 2,969 2020 10,752 2021 8,558 2022 8,558 2023 8,558 Thereafter 842 Total 40,237 Less: amount representing interest (5,556 ) Present value of lease liabilities $ 34,681 (1) Finance lease payments exclude $2.3 million of future payments required under signed lease agreements that have not yet commenced.
Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows (in thousands): For the three months ended September 30, 2019 For the nine months ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 786 $ 1,194 Financing cash flows from finance leases $ 5,432 $ 13,086 Non-cash right-of-use assets obtained in exchange for lease obligations: Finance leases $ 1,812 $ 42,114

Net Income per Share (Tables)

Net Income per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Basic and diluted net income per share was calculated as follows (in thousands, except per share data): For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Numerator: Net income $ 45,022 $ 52,591 $ 280,949 $ 322,597 Denominator: Weighted-average shares used to compute net income per share—basic 51,348 52,707 51,469 52,916 Dilutive restrictive stock awards 134 1 130 29 Weighted-average shares used to compute net income per share—diluted 51,482 52,708 51,599 52,945 Net income per share—basic and diluted $ 0.88 $ 1.00 $ 5.46 $ 6.10 Net income per share—diluted $ 0.87 $ 1.00 $ 5.44 $ 6.09

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities Measured on Recurring Basis	The following table presents information about the Company’s financial liabilities measured at fair value on a recurring basis as of December 31, 2018 and indicates the level of the fair value hierarchy utilized to determine such fair value (in thousands): Fair Value Measurements as of December 31, 2018 Using: Level 1 Level 2 Level 3 Total Liabilities: Natural gas swap contracts $ — $ 178 $ — $ 178

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Reconciliation of Revenue from Segments to Consolidated	The following tables include reconciliations of segment information to consolidated amounts (in thousands): For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Revenues Mining $ 280,841 $ 264,908 $ 1,037,950 $ 992,832 All other 6,665 8,396 25,458 24,815 Total revenues $ 287,506 $ 273,304 $ 1,063,408 $ 1,017,647
Reconciliation of Capital Expenditures from Segments to Consolidated	For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Capital Expenditures Mining 23,494 $ 22,924 $ 73,583 $ 76,422 All other 2,772 1,236 4,783 3,157 Total capital expenditures 26,266 $ 24,160 $ 78,366 $ 79,579
Reconciliation of Net Income (Loss) from Segments to Consolidated	Below is a reconciliation of Segment Adjusted EBITDA to net income, which is its most directly comparable financial measure calculated and presented in accordance with GAAP (in thousands): For the three months ended For the nine months ended September 30, 2019 2018 2019 2018 Segment Adjusted EBITDA $ 90,620 $ 97,720 $ 459,912 $ 456,425 Other revenues 6,665 8,396 25,458 24,815 Cost of other revenues (7,583 ) (6,704 ) (23,346 ) (21,826 ) Depreciation and depletion (25,741 ) (26,071 ) (73,652 ) (71,750 ) Selling, general and administrative (9,362 ) (7,357 ) (29,050 ) (29,056 ) Transaction and other expenses — (3,265 ) — (7,539 ) Loss on early extinguishment of debt — — (9,756 ) — Other income 5,272 — 22,815 — Interest expense, net (7,250 ) (10,128 ) (22,793 ) (28,472 ) Income tax expense (7,599 ) — (68,639 ) — Net income $ 45,022 $ 52,591 $ 280,949 $ 322,597

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 208,673	$ 205,577
Restricted cash included in other long-term assets	830	828
Total cash and cash equivalents and restricted cash included in the Condensed Statements of Cash Flows	$ 209,503	$ 206,405	$ 130,982	$ 36,264

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Short-Term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2019
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments	$ 17,501	$ 24,171
Cash and Fixed Income Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments		24,200
Treasury bills
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments	$ 17,500
Maturity term for short-term investments	6 months
Fixed Income Securities
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments		$ 14,300

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Revenue Recognition (Details) $ in Thousands	3 Months Ended		9 Months Ended		14 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Mar. 31, 2018t
Concentration Risk [Line Items]
Percent of total production transferred for title and marketing					10.00%
Maximum total production transferred for title and marketing | t					250,000
Other revenues	$ 287,506	$ 273,304	$ 1,063,408	$ 1,017,647
XCoal | Customer Concentration Risk | Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	21.00%	5.00%	21.00%	16.00%
Other revenues	$ 57,800	$ 12,800	$ 220,800	$ 157,800

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Leases (Details) $ in Thousands	Sep. 30, 2019USD ($)
Accounting Policies [Abstract]
Right-of-use asset	$ 41,165
Short term financing lease liabilities	9,614
Long term financing lease liabilities	$ 27,367

Inventories, net (Details)

Inventories, net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Coal	$ 55,561	$ 32,854
Raw materials, parts, supplies and other, net	26,357	23,865
Total inventories, net	$ 81,918	$ 56,719

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income tax expense	$ (7,599,000)	$ 0	$ (68,639,000)	$ 0

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt discount/premium, net	$ (4,415)	$ (6,769)
Total debt	339,020	468,991
Less: current debt	0	(760)
Total long-term debt	339,020	468,231
Senior secured notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 343,435	475,000
Weighted average interest rate	8.00%
Promissory note
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	$ 760

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	Feb. 21, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 25, 2019	Mar. 22, 2019	Mar. 01, 2018	Nov. 02, 2017
Debt Instrument [Line Items]
Amount that can be authorized without making an offer to buy back debt						$ 299,401,000
Loss on early extinguishment of debt		$ 0	$ 0	$ 9,756,000	$ 0
Senior secured notes | Senior Secured Notes Due 2024, New Notes
Debt Instrument [Line Items]
Face amount of debt								$ 125,000,000
Transaction costs			$ 500,000		$ 4,500,000
Senior secured notes | Senior Secured Notes Due 2024, Existing Notes, Restricted Payment Offer
Debt Instrument [Line Items]
Maximum amount available for repurchase	$ 150,000,000
Stated interest rate								8.00%
Redemption price, percentage	103.00%
Debt instrument, amount validly tendered and not withdrawn							$ 1,900,000
Pro-ration factor							31.5789%
Purchase integrals							$ 1,000
Senior secured notes | Senior Secured Notes Due 2024, Tendered Notes, Restricted Payment Pro-Rated Offer
Debt Instrument [Line Items]
Debt instrument, amount validly tendered and not withdrawn							599,000
Debt instrument, amount accepted							599,000
Debt instrument, not accepted							1,301,000
Senior secured notes | Senior Secured Notes Due 2024, Existing Notes
Debt Instrument [Line Items]
Face amount of debt									$ 350,000,000
Stated interest rate									8.00%
Senior secured notes | Senior Secured Notes Due 2024, Existing Notes, Tender Offer
Debt Instrument [Line Items]
Maximum amount available for repurchase	$ 150,000,000
Redemption price, percentage	104.25%
Debt instrument, amount validly tendered and not withdrawn							$ 415,099,000
Pro-ration factor							31.5789%
Purchase integrals							$ 1,000
Senior secured notes | Senior Secured Notes Due 2024, Tendered Notes, Tender Offer Pro-Rated Offer
Debt Instrument [Line Items]
Debt instrument, amount validly tendered and not withdrawn							130,966,000
Debt instrument, amount accepted							130,966,000
Debt instrument, not accepted							$ 284,133,000

Other Long-Term Liabilities (De

Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Black lung obligations	$ 25,413	$ 25,206
Other	942	5,510
Total other long-term liabilities	$ 26,355	$ 30,716

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Lessor, Lease, Description [Line Items]
Finance leases that have not yet commenced	$ 2.3
Minimum
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Finance leases not yet commenced, term	1 year
Maximum
Lessor, Lease, Description [Line Items]
Remaining lease terms	5 years
Finance leases not yet commenced, term	2 years

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information (Details) $ in Thousands	Sep. 30, 2019USD ($)
Leases [Abstract]
Finance lease right-of-use assets, net(1)	$ 41,165
Finance lease liabilities
Current	9,614
Noncurrent	27,367
Total finance lease liabilities	$ 36,981
Weighted average remaining lease term - finance leases (in months)	3 years 11 months 12 days
Weighted average discount rate - finance leases(2)	6.00%
Accumulated amortization	$ 4,800

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Operating lease cost	$ 688	$ 1,866
Finance lease cost:
Amortization of leased assets	2,120	7,950
Interest on lease liabilities	786	1,194
Net lease cost	$ 3,594	$ 11,010

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) $ in Thousands	Sep. 30, 2019USD ($)
Leases [Abstract]
2019	$ 2,969
2020	10,752
2021	8,558
2022	8,558
2023	8,558
Thereafter	842
Total	40,237
Less: amount representing interest	(5,556)
Present value of lease liabilities	34,681
Future payments required under signed lease agreements that have not yet commenced	$ 2,300

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from finance leases	$ 786	$ 1,194
Financing cash flows from finance leases	5,432	13,086
Non-cash right-of-use assets obtained in exchange for lease obligations:
Non-cash right-of-use assets obtained in exchange for finance lease obligations	$ 1,812	$ 42,114

Net Income per Share - Schedule

Net Income per Share - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 45,022	$ 52,591	$ 280,949	$ 322,597
Denominator:
Weighted average number of shares outstanding—basic (in shares)	51,348	52,707	51,469	52,916
Dilutive restrictive stock awards	134	1	130	29
Weighted average number of shares outstanding—diluted (in shares)	51,482	52,708	51,599	52,945
Net income per share—basic and diluted (in dollars per share)	$ 0.88	$ 1	$ 5.46	$ 6.10
Net income per share—diluted (in dollars per share)	$ 0.87	$ 1	$ 5.44	$ 6.09

Net Income per Share - Narrativ

Net Income per Share - Narrative (Details) - USD ($) $ in Thousands	Feb. 08, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Dilutive awards (in shares)		134,000	1,000	130,000	29,000
2016 Equity Plan
Class of Stock [Line Items]
Dilutive awards (in shares)		72,366		69,484
Phantom Share Units (PSUs) | 2016 and 2017 Equity Plans
Class of Stock [Line Items]
Settlement period				5 years
Phantom Share Units (PSUs) | 2016 Equity Plan
Class of Stock [Line Items]
Common stock shares contingently issuable (in shares)				43,580
Restricted Stock Units (RSUs) | 2017 Equity Plan
Class of Stock [Line Items]
Common stock shares contingently issuable (in shares)				13,157
Restricted Stock Units (RSUs) | 2017 Equity Plan, 2019 Award
Class of Stock [Line Items]
Restricted stock unit awards awarded (in shares)	306,314
Stock compensation expense		$ 900		$ 2,200
Restricted Stock Units (RSUs) | 2017 Equity Plan, Additional 2019 Award
Class of Stock [Line Items]
Stock compensation expense		$ 129		343
Restricted stock unit awards awarded, value				$ 1,500
Shares to be issued upon settlement of awards (in shares)		76,844		76,844
Dilutive awards (in shares)		22,243		25,617
Service-based RSUs | 2016 Equity Plan
Class of Stock [Line Items]
RSUs excluded from computation of earnings per share (in shares)				98,216
Service-based RSUs | 2017 Equity Plan
Class of Stock [Line Items]
RSUs excluded from computation of earnings per share (in shares)				161,998
Dilutive awards (in shares)		39,983		34,922
Service-based RSUs | 2017 Equity Plan, 2019 Award
Class of Stock [Line Items]
Vesting period				3 years
Performance and market-based RSUs | 2017 Equity Plan
Class of Stock [Line Items]
RSUs excluded from computation of earnings per share (in shares)				271,589
Performance and market-based RSUs | 2017 Equity Plan, 2019 Award
Class of Stock [Line Items]
Vesting period				3 years

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Nov. 05, 2015
Black Warrior Methane (BWM)
Related Party Transaction [Line Items]
Proportionate consolidation method, ownership percentage					50.00%
Black Warrior Transmission (BWT)
Related Party Transaction [Line Items]
Equity method investment, ownership percentage					50.00%
Allocated Expenses to Joint Venture | Corporate Joint Venture
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 0.6	$ 0.8	$ 1.1	$ 2.3

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Aug. 31, 2019	May 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Settlement proceeds	$ 5,300,000	$ 17,500,000			$ 22,800,000
Throughput obligation			$ 0		0		$ 0
Coal royalty expense			$ 19,700,000	$ 19,900,000	$ 75,700,000	$ 74,100,000

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($)	Jul. 23, 2019	Apr. 23, 2019	Feb. 19, 2019	Aug. 08, 2018	Jun. 14, 2018	May 10, 2018	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 26, 2019	Mar. 25, 2019	Dec. 31, 2018	May 02, 2018	Apr. 12, 2017
Class of Stock [Line Items]
Common stock shares authorized (in shares)								140,000,000				140,000,000		140,000,000
Common stock par value (in dollars per share)								$ 0.01				$ 0.01		$ 0.01
Preferred stock shares authorized (in shares)								10,000,000				10,000,000		10,000,000
Preferred stock par value (in dollars per share)								$ 0.01				$ 0.01		$ 0.01
Remaining authorized repurchase amount											$ 299,401,000
Dividends declared (in dollars per share)	$ 0.05	$ 0.05	$ 0.05
Regular quarterly cash dividend	$ 2,600,000	$ 2,600,000	$ 2,600,000
Special cash dividend		$ 230,000,000
New Stock Repurchase Program
Class of Stock [Line Items]
Authorized amount of stock to be repurchased, value										$ 70,000,000
Shares repurchased (in shares)								500,000
Treasury stock purchase, value								$ 10,600,000
Remaining authorized repurchase amount								$ 58,800,000
The First Stock Repurchase Program
Class of Stock [Line Items]
Authorized amount of stock to be repurchased, value													$ 40,000,000
The Stock Repurchase
Class of Stock [Line Items]
Shares repurchased (in shares)						500,000
Treasury stock retired, value						$ 12,100,000
Secondary Equity Offerings
Class of Stock [Line Items]
Payments of Stock Issuance Costs							$ 2,800,000		$ 3,000,000
May 2018 Equity Offering
Class of Stock [Line Items]
Number of shares sold (in shares)						8,000,000
Shares sold (in USD per share)						$ 24.20
June 2018 Equity Offering
Class of Stock [Line Items]
Number of shares sold (in shares)					5,000,000
Shares sold (in USD per share)					$ 28.35
August 2018 Equity Offering
Class of Stock [Line Items]
Number of shares sold (in shares)				2,204,806
Shares sold (in USD per share)				$ 25.40

Derivative Instruments (Details

Derivative Instruments (Details) - Not Designated as Hedging Instrument - Natural gas swap contracts	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)BTU	Dec. 31, 2018USD ($)BTU
Commodity Contract, Maturity Q4 2018
Derivative [Line Items]
Derivative energy measure (in BTUs) | BTU	0	2,100,000,000
Commodity Contract
Derivative [Line Items]
Natural gas swap contracts, current liability | $	$ 0	$ 200,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 339,020,000	$ 468,231,000
Letters of credit outstanding	8,900,000	0
Fair Value, Measurements, Recurring | Commodity Contract | Natural gas swap contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Natural gas swap contracts, asset		178,000
Fair Value, Measurements, Recurring | Commodity Contract | Natural gas swap contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Natural gas swap contracts, asset		0
Fair Value, Measurements, Recurring | Commodity Contract | Natural gas swap contracts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Natural gas swap contracts, asset		178,000
Fair Value, Measurements, Recurring | Commodity Contract | Natural gas swap contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Natural gas swap contracts, asset		0
ABL Facility | Revolving credit facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of borrowings available	116,100,000
Senior Secured Notes Due 2024, Existing Notes | Senior secured notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	0
Senior Secured Notes Due 2024, Existing Notes | Senior secured notes | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of debt instrument	$ 357,200,000
Revolving credit facility | Citibank | Letter of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Letters of credit issued and outstanding		$ 4,600,000

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2019segment
Segment Reporting [Abstract]
Number of operating segments	2
Number of reportable segments	1

Segment Information - Reconcili

Segment Information - Reconciliation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 287,506	$ 273,304	$ 1,063,408	$ 1,017,647
Mining | Mining | Operating Segments
Segment Reporting Information [Line Items]
Total revenues	280,841	264,908	1,037,950	992,832
All other
Segment Reporting Information [Line Items]
Total revenues	6,665	$ 8,396	25,458	$ 24,815
All other | Segment Reconciling Items
Segment Reporting Information [Line Items]
Total revenues	$ 6,665		$ 25,458

Segment Information - Reconci_2

Segment Information - Reconciliation of Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Capital Expenditures	$ 26,266	$ 24,160	$ 78,366	$ 79,579
Segment Reconciling Items
Segment Reporting Information [Line Items]
Capital Expenditures	2,772	1,236	4,783	3,157
Mining | Operating Segments
Segment Reporting Information [Line Items]
Capital Expenditures	$ 23,494	$ 22,924	$ 73,583	$ 76,422

Segment Information - Reconci_3

Segment Information - Reconciliation of Net Income (Loss) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from External Customer [Line Items]
Segment Adjusted EBITDA	$ 90,620,000	$ 97,720,000	$ 459,912,000	$ 456,425,000
Other revenues	287,506,000	273,304,000	1,063,408,000	1,017,647,000
Cost of other revenues	(7,583,000)	(6,704,000)	(23,346,000)	(21,826,000)
Depreciation and depletion	(25,741,000)	(26,071,000)	(73,652,000)	(71,750,000)
Selling, general and administrative	(9,362,000)	(7,357,000)	(29,050,000)	(29,056,000)
Transaction and other expenses	0	(3,265,000)	0	(7,539,000)
Loss on early extinguishment of debt	0	0	(9,756,000)	0
Other income	5,272,000	0	22,815,000	0
Interest expense, net	(7,250,000)	(10,128,000)	(22,793,000)	(28,472,000)
Income tax expense	(7,599,000)	0	(68,639,000)	0
Net income	45,022,000	52,591,000	280,949,000	322,597,000
Other revenues
Revenue from External Customer [Line Items]
Other revenues	$ 6,665,000	$ 8,396,000	$ 25,458,000	$ 24,815,000

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 18, 2019	Jul. 23, 2019	Apr. 23, 2019	Feb. 19, 2019
Subsequent Event [Line Items]
Dividends declared (in dollars per share)		$ 0.05	$ 0.05	$ 0.05
Regular quarterly cash dividend		$ 2.6	$ 2.6	$ 2.6
Subsequent Event
Subsequent Event [Line Items]
Dividends declared (in dollars per share)	$ 0.05
Regular quarterly cash dividend	$ 2.6