Warrior Met Coal (HCC) 10-Q 9 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2017	Nov. 06, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	WARRIOR MET COAL, INC.
Entity Central Index key	1,691,303
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Amendment Flag	false
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		53,446,284

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - Successor - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 234,053	$ 150,045
Short-term investments	17,501	17,501
Trade accounts receivable	128,541	65,896
Other receivables	19,881	5,901
Inventories, net	33,902	39,420
Prepaid expenses	18,958	12,010
Total current assets	452,836	290,773
Mineral interests, net	132,329	143,231
Property, plant and equipment, net	514,066	496,959
Other long-term assets	21,394	16,668
Total assets	1,120,625	947,631
Current liabilities:
Accounts payable	16,593	6,043
Accrued expenses	54,168	47,339
Other current liabilities	4,538	8,405
Current portion of long-term debt	2,936	2,849
Total current liabilities	78,235	64,636
Long-term debt	1,512	3,725
Asset retirement obligations	98,232	96,050
Other long-term liabilities	28,253	30,253
Total liabilities	206,232	194,664
Commitments and contingencies
Stockholders’ Equity:
Common stock, $0.01 par value per share (Authorized -140,000,000 shares, issued and outstanding - 53,446,284 and 53,442,532, respectively)	534	533
Preferred stock, $0.01 par value per share (10,000,000 shares authorized, no shares issued and outstanding)	0	0
Additional paid in capital	610,992	802,107
Retained earnings (accumulated deficit)	302,867	(49,673)
Total stockholders’ equity	914,393	752,967
Total liabilities and stockholders’ equity	$ 1,120,625	$ 947,631

CONDENSED BALANCE SHEETS CONDEN

CONDENSED BALANCE SHEETS CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
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)	53,446,284	53,442,532
Common stock shares outstanding (in shares)	53,446,284	53,442,532
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

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
Revenues:
Sales	$ 302,958,000	$ 44,395,000		$ 129,810,000	$ 895,802,000
Other revenues	8,997,000	8,496,000		14,555,000	33,487,000
Total revenues	311,955,000	52,891,000		144,365,000	929,289,000
Costs and expenses:
Cost of sales (exclusive of items shown separately below)	189,564,000	51,787,000		155,653,000	455,860,000
Cost of other revenues (exclusive of items shown separately below)	6,985,000	6,998,000		12,124,000	22,959,000
Depreciation and depletion	23,393,000	22,538,000		38,359,000	57,625,000
Selling, general and administrative	9,243,000	4,516,000		10,331,000	23,073,000
Other postretirement benefits	0	0		0	0
Restructuring costs	0	0		0	0
Transaction and other costs	0	0		10,475,000	12,873,000
Total costs and expenses	229,185,000	85,839,000		226,942,000	572,390,000
Operating income (loss)	82,770,000	(32,948,000)		(82,577,000)	356,899,000
Interest (expense), net	(640,000)	(694,000)		(1,128,000)	(1,890,000)
Reorganization items, net	0	0		0	0
Income (loss) before income taxes	82,130,000	(33,642,000)		(83,705,000)	355,009,000
Income tax (benefit) expense	(37,587,000)	0		0	(2,881,000)
Net income (loss)	$ 119,717,000	$ (33,642,000)		$ (83,705,000)	$ 357,890,000
Basic and diluted net income (loss) per share:
Net income (loss) per share—basic and diluted (in dollars per share)	$ 2.27	$ (0.64)		$ (1.59)	$ 6.79
Weighted average number of shares outstanding—basic and diluted (in shares)	52,777	52,640		52,640	52,727
Dividends per share (in dollars per share)	$ 0.05	$ 0		$ 0	$ 3.66
Predecessor
Revenues:
Sales			$ 65,154,000
Other revenues			6,229,000
Total revenues			71,383,000
Costs and expenses:
Cost of sales (exclusive of items shown separately below)			72,297,000
Cost of other revenues (exclusive of items shown separately below)			4,698,000
Depreciation and depletion			28,958,000
Selling, general and administrative			9,008,000
Other postretirement benefits			6,160,000
Restructuring costs			3,418,000
Transaction and other costs			0
Total costs and expenses			124,539,000
Operating income (loss)			(53,156,000)
Interest (expense), net			(16,562,000)
Reorganization items, net			7,920,000
Income (loss) before income taxes			(61,798,000)
Income tax (benefit) expense			18,000
Net income (loss)			$ (61,816,000)

CONDENSED STATEMENT OF CHANGES

CONDENSED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY - 9 months ended Sep. 30, 2017 - Successor - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Preferred Stock	Additional Paid in Capital	Retained Earnings (Accumulated deficit)
Balance at beginning of period at Dec. 31, 2016	$ 752,967	$ 533	$ 0	$ 802,107	$ (49,673)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	357,890				357,890
Dividends paid ($3.66 per share)	(195,350)			(190,000)	(5,350)
Purchase accounting measurement period adjustment	(3,525)			(3,525)
Equity award modification	1,255			1,255
Stock compensation	$ 1,155			1,155
Common shares issued (in shares)	1	1
Balance at end of period at Sep. 30, 2017	$ 914,393	$ 534	$ 0	$ 610,992	$ 302,867

CONDENSED STATEMENT OF CHANGES6

CONDENSED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
Dividends per share (in dollars per share)	$ 0.05	$ 0	$ 0	$ 3.66

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
OPERATING ACTIVITIES
Net income (loss)	$ 119,717	$ (33,642)		$ (83,705)	$ 357,890
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and depletion	23,393	22,538		38,359	57,625
Deferred income tax (benefit) expense	(5,373)	0		0	(5,373)
Stock based compensation expense	233	0		125	1,155
Non-cash reorganization items	0	0		0	0
Amortization of debt issuance costs and debt discount, net	427	454		830	1,316
Accretion of asset retirement obligations	940	1,227		1,962	2,839
Changes in operating assets and liabilities:
Trade accounts receivable	(35,990)	22,588		(5,453)	(62,645)
Other receivables	(15,181)	(1,696)		(1,572)	(13,981)
Inventories	37,003	(5,876)		8,801	4,072
Prepaid expenses and other current assets	(2,274)	1,369		(8,306)	(6,948)
Accounts payable	2,772	(1,544)		(8,893)	10,550
Accrued expenses and other current liabilities	(9,015)	1,111		29,704	1,002
Other	(543)	992		6,781	(4,436)
Net cash provided by (used in) operating activities	116,109	7,521		(21,367)	343,066
INVESTING ACTIVITIES
Purchase of property, plant and equipment	(34,408)	(2,435)		(8,449)	(62,671)
Proceeds from sale of property, plant and equipment	0	0		34	0
Cash paid for acquisition, net of cash acquired	0	76		(24,031)	0
Cash receipt from escrow agreement	0	(3,493)		9,364
Proceeds from termination of life insurance policy	0	29,857		12,857	0
Purchases of short-term investments	0	(17,505)		(17,505)	0
Net cash provided by (used in) investing activities	(34,408)	6,500		(27,730)	(62,671)
FINANCING ACTIVITIES
Dividends paid	(2,677)	0		0	(195,350)
Proceeds from rights offering				200,000
Proceeds from issuance of debt	0	0		0	0
Retirements of debt	(763)	(765)		(1,530)	(2,294)
Net cash transfers to Parent	0	0		0	0
Debt issuance costs paid	0	(463)		(4,978)	0
Net cash provided by (used in) financing activities	(3,440)	(1,228)		193,492	(197,644)
Net increase (decrease) in cash and cash equivalents and restricted cash	78,261	12,793		144,395	82,751
Cash and cash equivalents and restricted cash at beginning of period	157,146	131,602		0	152,656
Cash and cash equivalents and restricted cash at end of period	$ 235,407	$ 144,395	$ 0	144,395	$ 235,407
Predecessor
OPERATING ACTIVITIES
Net income (loss)			(61,816)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and depletion			28,958
Deferred income tax (benefit) expense			18
Stock based compensation expense			390
Non-cash reorganization items			(18,882)
Amortization of debt issuance costs and debt discount, net			10,164
Accretion of asset retirement obligations			1,169
Changes in operating assets and liabilities:
Trade accounts receivable			15,097
Other receivables			1,070
Inventories			677
Prepaid expenses and other current assets			13,020
Accounts payable			(15,338)
Accrued expenses and other current liabilities			(16,083)
Other			858
Net cash provided by (used in) operating activities			(40,698)
INVESTING ACTIVITIES
Purchase of property, plant and equipment			(5,422)
Proceeds from sale of property, plant and equipment			0
Cash paid for acquisition, net of cash acquired			0
Proceeds from termination of life insurance policy			0
Purchases of short-term investments			0
Net cash provided by (used in) investing activities			(5,422)
FINANCING ACTIVITIES
Dividends paid			0
Proceeds from issuance of debt			15,723
Retirements of debt			(285)
Net cash transfers to Parent			(13,290)
Debt issuance costs paid			(8,388)
Net cash provided by (used in) financing activities			(6,240)
Net increase (decrease) in cash and cash equivalents and restricted cash			(52,360)
Cash and cash equivalents and restricted cash at beginning of period			84,462	$ 32,102
Cash and cash equivalents and restricted cash at end of period			$ 32,102

Business and Basis of Presentat

Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2017
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, LLC (the “Company” or, for the periods beginning as of April 1, 2016, the “Successor”) was formed on September 3, 2015 by certain Walter Energy, Inc. (“Walter Energy” or the “Parent”) lenders under the 2011 Credit Agreement, dated as of April 1, 2011 (the “2011 Credit Agreement”) and the noteholders under the 9.50% Senior Secured Notes due 2019 (such lenders and noteholders, collectively, “Walter Energy’s First Lien Lenders”) in connection with the acquisition by the Company of certain core operating assets of Walter Energy under section 363 under Chapter 11 of Title 11 (the "Chapter 11 Cases") of the U.S. Bankruptcy Code (“U.S. Bankruptcy Code”) in the Northern District of Alabama, Southern Division (the "Bankruptcy Court"). These operating assets acquired and liabilities assumed are referred to as the “Predecessor” for all periods on or before March 31, 2016. The Company and its Predecessor are a U.S. based producer and exporter of metallurgical (“met”) coal for a diversified customer base of blast furnace steel producers located primarily in Europe and South America. 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. On November 5, 2015, Walter Energy and certain of its wholly owned U.S. subsidiaries (collectively, the "Walter Energy Debtors") entered into an asset purchase agreement (as amended, the “Asset Purchase Agreement”) with the Company, pursuant to which, among other things, the Company, on behalf of Walter Energy’s First Lien Lenders, agreed to acquire the Predecessor through a credit bid of $ 1.1 billion and a release of the liens under the 2011 Credit Agreement and the 9.50% Senior Secured Notes due 2019 (“Walter Energy First Lien Obligations”), to assume certain liabilities of the Walter Energy Debtors and to pay cash consideration in accordance with sections 363 and 365 of the U.S. Bankruptcy Code (the “Asset Acquisition”). On January 8, 2016, the Bankruptcy Court approved the Asset Acquisition, which closed on March 31, 2016. In connection with the Asset Acquisition, the Company also conducted rights offerings to Walter Energy’s First Lien Lenders and certain qualified unsecured creditors to purchase newly issued Class B Units of the Company, which diluted the Class A Units on a pro rata basis (the “Rights Offerings”). Proceeds from the Rights Offerings were used to pay certain costs associated with the Asset Acquisition and for general working capital purposes. Special Distribution On March 31, 2017, the Company's board of managers declared a cash distribution payable to holders of its then outstanding Class A Units, Class B Units and Class C Units as of March 27, 2017, resulting in distributions to such holders in the aggregate amount of $ 190.0 million (the “Special Distribution”). The Special Distribution was funded with available cash on hand and was paid to Computershare Trust Company, N.A., as disbursing agent, on March 31, 2017. Corporate Conversion and Initial Public Offering On April 12, 2017, in connection with the Company’s initial public offering (“IPO”), Warrior Met Coal, LLC filed a certificate of conversion, whereby Warrior Met Coal, LLC effected a corporate conversion from a Delaware limited liability company to a Delaware corporation and changed its name to Warrior Met Coal, Inc. In connection with this corporate conversion, the Company filed a certificate of incorporation. 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. All references in the unaudited interim condensed financial statements to the number of shares and per share amounts of common stock have been retroactively recast to reflect the corporate conversion. On April 19, 2017, the Company completed its IPO whereby the selling stockholders named in the Registration Statement on Form S-1 (File No. 333-216499) sold 16,666,667 shares of common stock at a price to the public of $ 19.00 per share. The Company did not receive any proceeds from the sale of common stock in the IPO, and will not receive any proceeds from the exercise of the underwriters’ option to purchase additional shares of common stock, if any. All of the net proceeds from the IPO were received by the selling stockholders. The aggregate net proceeds to the selling stockholders in the IPO were $296.9 million , net of underwriting discounts and commissions of $19.8 million . The Company has paid cumulative offering expenses of $15.9 million on behalf of the selling stockholders. Upon the closing of the IPO, 53,442,532 shares of common stock were outstanding. On April 13, 2017, our common stock began trading on the New York Stock Exchange under the ticker symbol "HCC" and on April 19, 2017, we closed our IPO. Basis of Presentation Prior to the closing of the Asset Acquisition on March 31, 2016, the Company had no operations and nominal assets. The accompanying financial statements have been presented on a condensed consolidated basis for the “Successor” periods subsequent to the Asset Acquisition, which include the three and nine months ended September 30, 2017 , the three and six months ended September 30, 2016 and on a condensed combined basis for the “Predecessor” periods prior to the Asset Acquisition, which includes the three months ended March 31, 2016. The financial information of the Company has been separated by a vertical line on the face of the financial statements to identify these different bases of accounting for Predecessor and Successor periods. 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. Operating results for the three and nine months ended September 30, 2017 (Successor) and the three and six months ended September 30, 2016 (Successor) are not necessarily indicative of the final results that may be expected for the year ended December 31, 2017. These unaudited financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2016 included in the final prospectus for the IPO dated April 12, 2017 and filed pursuant to Rule 424(b)(4) with the Securities and Exchange Commission (the “SEC”) on April 14, 2017 (the “IPO Prospectus”), which is part of our registration statement on Form S-1 (File No. 333-216499). Predecessor Presentation The Predecessor’s condensed combined financial statements for the three months ended March 31, 2016, have been “carved-out” from the accounting records of Walter Energy. Historically, the Predecessor did not operate as an independent standalone company. For periods subsequent to filing the Chapter 11 Cases and prior to March 31, 2016, the Predecessor applied the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 852, Reorganizations, in preparing its condensed combined financial statements. ASC 852 requires that the financial statements distinguish transactions and events that are directly associated with the reorganization from the ongoing operations of the business. Accordingly, certain revenues, expenses, realized gains and losses and provisions for losses that were realized or incurred in the Chapter 11 Cases have been recorded in a reorganization line item on the Condensed Combined Statements of Operations. Preparation of the condensed combined financial statements for the three months ended March 31, 2016, included making certain adjustments necessary to reflect all costs of doing business to present the historical records on a basis as if the Predecessor had been a separate stand alone entity. These adjustments include, for example, allocations of Parent overhead and selling, general and administrative expenses. The historical costs and expenses reflected in the condensed combined financial statements include an allocation for certain corporate functions historically provided by the Parent. Substantially all of the Predecessor’s senior management were employed by the Parent and certain functions critical to the Predecessor’s operations were centralized and managed by the Parent. Historically, the centralized functions have included executive senior management, financial reporting, financial planning and analysis, accounting, shared services, information technology, tax, risk management, treasury, legal, human resources, and strategy and development. The costs of each of these services has been allocated to the Predecessor on the basis of the Predecessor’s relative headcount, revenue and total assets to that of the Parent. These cost allocations were $ 7.8 million for the three months ended March 31, 2016 (Predecessor). All intracompany transactions have been eliminated. The net effect of the settlement of transactions between the Predecessor, the Parent and other affiliates of the Parent, together with cash transfers to and from the Parent’s cash management accounts are reflected in the Condensed Statements of Changes in Stockholders' Equity and Parent Net Investment as net transfers to Parent and in the Condensed Statements of Cash Flows as a financing activity. The allocation methodologies have been described in the notes to the financial statements where appropriate, and management considers the allocations to be reasonable. The financial information included herein may not necessarily reflect the financial position, results of operations and cash flows of the Predecessor in the future or what they would have been had the Predecessor been a separate, standalone entity during the periods presented.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
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 our IPO Prospectus. 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): Successor September 30, 2017 December 31, 2016 Cash and cash equivalents $ 234,053 $ 150,045 Restricted cash included in other long-term assets 1,354 2,611 Total cash and cash equivalents and restricted cash included in the Statements of Cash Flows $ 235,407 $ 152,656 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, 2017 (Successor) and December 31, 2016 (Successor), restricted cash included in other long-term assets in the Condensed Balance Sheet represents amounts funded to an escrow account as collateral for coal royalties due under certain underground coal mining lease contracts. 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 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. Securities classified as held to maturity securities are those securities that management has the intent and ability to hold to maturity. As of September 30, 2017 (Successor) and December 31, 2016 (Successor), the Company’s short-term investments consisted of $17.5 million in Treasury bills with a maturity of six months . These 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 and its subsidiaries, which were assumed in the Asset Acquisition and relate to periods prior to March 31, 2016. New Accounting Pronouncements In September 2015, the FASB issued Accounting Standards Update ("ASU") 2015-16, “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments,” which eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively. Instead, an acquirer will recognize a measurement-period adjustment during the period in which it determines the amount of the adjustment. The guidance is effective for public business entities for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. We adopted the amendments of ASU 2015-16, effective January 1, 2017. We recognized a $3.5 million measurement-period adjustment during the three months ended March 31, 2017 (Successor), which we reflected prospectively (see Note 3). In May 2014, the FASB issued ASU 2014-09 “Revenue from Contracts with Customers”. The new standard requires an entity to recognize revenue upon transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance also requires additional disclosures about the nature, amount, timing, and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date,” which defers the effective date of ASU 2014-09 by one year. ASU 2015-09 is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period and permits early adoption on a limited basis. The Company plans to adopt ASU 2014-09 as of January 1, 2018, using the modified retrospective approach. Based on the current status of the Company’s assessment of the new standard, the Company does not anticipate any significant changes to the current timing or method for recognizing revenue. Additionally, the Company does not anticipate the new standard to have a material impact on our financial statements outside of the expanded disclosure requirements.

Acquisition of the Predecessor

Acquisition of the Predecessor	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Acquisition of the Predecessor	Acquisition of the Predecessor On November 5, 2015, the Walter Energy Debtors entered into the Asset Purchase Agreement with the Company, pursuant to which, among other things, the Company, on behalf of Walter Energy’s First Lien Lenders, agreed to acquire the Predecessor via a credit bid and release of the liens on the Walter Energy First Lien Obligations. On January 8, 2016, the Bankruptcy Court approved the Asset Acquisition, which closed on March 31, 2016. The cash consideration of $ 50.8 million included the funding of escrow accounts to be used to pay certain expenses on behalf of the Walter Energy Debtors, some of which required residual amounts contained in the escrow accounts to be refunded to the Company after a specified time period. The net cash paid for the Asset Acquisition was $ 24.1 million , which was $ 50.8 million of cash paid less cash and cash equivalents acquired of $ 26.7 million . The purchase consideration has been allocated to the assets acquired and liabilities assumed based upon their estimated fair values at the date of the Asset Acquisition. During the first quarter of 2017, the Company completed the valuation of the assets and liabilities with the assistance of an independent third party and recorded a measurement-period adjustment to the preliminary purchase price allocation. The measurement-period adjustment was due to updated estimates for the acquired mineral interests including estimates for future royalty income, production volumes and timing which resulted in a $3.5 million decrease in fair value allocated to mineral interests as compared to the December 31, 2016 preliminary fair value. This also resulted in a decrease to additional paid in capital. The measurement-period adjustment was recorded during the first quarter of 2017 and had no impact on reported earnings for the three and nine months ended September 30, 2017 (Successor). In determining the fair values of net assets acquired in the Asset Acquisition, the Company considered, among other factors, the analyses of the Predecessor’s historical financial performance and estimates of the future performance of the acquired business, as well as the highest and best use of the acquired assets. Working capital, excluding inventory, and non-current restricted cash were recorded at the Predecessor’s carrying value, which is representative of the fair value on the date of acquisition. Inventory was valued at its net realizable value. Mineral interest was recorded at fair value utilizing the income approach. The income approach utilized the Company’s operating projections as of the valuation date. Under the income approach, fair value was estimated based upon the present value of future cash flows. A number of significant assumptions and estimates were involved in forecasting the future cash flows including sales volumes and prices, costs to produce (including costs for labor, commodity supplies and contractors), transportation costs, capital spending, working capital changes and a risk adjusted, after-tax cost of capital (all of which generally constitute unobservable Level 3 inputs under the fair value hierarchy). Property, plant and equipment, and other assets were recorded at fair values based on the cost and market approaches. The cost approach utilized trending and direct costing techniques to develop replacement costs. The market approach is based on independent secondary market data (which generally constitute Level 2 inputs under the fair value hierarchy). Black lung obligations and asset retirement obligations were recorded at fair value using a combination of market data, operational data and discounted cash flows and were adjusted by a discount rate factor reflecting current market conditions at the time of acquisition. The following tables summarize the final purchase price allocation, including the applicable measurement-period adjustments made upon finalization during the first quarter of 2017 (in thousands): Final purchase price: Cash paid $ 50,830 Fair value of First Lien Obligations relinquished in exchange for net assets of the Predecessor 598,607 Total purchase price $ 649,437 Final fair values of assets acquired and liabilities assumed: Cash and cash equivalents $ 26,723 Trade and other receivables 14,358 Inventories 46,464 Prepaid expenses and other current assets 30,722 Mineral interests 144,224 Property, plant and equipment 533,441 Other long-term assets 28,865 Total assets 824,797 Accounts payable 10,470 Accrued expenses 12,843 Other current liabilities 24,044 Current debt 2,879 Long-term debt 5,758 Deferred income taxes 1,400 Other long-term liabilities 117,966 Total liabilities 175,360 Total fair value of net assets acquired $ 649,437 Supplemental Unaudited Pro Forma Financial Information The following unaudited pro forma results of operations give effect to the Asset Acquisition as if it had occurred on January 1, 2015. This unaudited pro forma financial information should not be relied upon as necessarily being indicative of the historical results that would have been obtained if the Asset Acquisition had actually occurred on that date, nor the results of operations in the future. The 2016 supplemental unaudited pro forma financial information was adjusted to (i) reflect the impact of certain fair value adjustments, including an adjustment to depreciation and depletion expense as a result of a change in the basis of Property, Plant and Equipment and Mineral Interests, (ii) eliminate historical interest expense related to the notes, loans and other debt that was not assumed by the Company as part of the Asset Acquisition, (iii) eliminate a gain on reorganization items associated with the Chapter 11 Cases and (iv) eliminate the Predecessor's historical other postretirement benefit expense associated with the Predecessor's historical other postretirement benefit obligations for retiree medical and life insurance benefits, which were not assumed by the Company. Predecessor For the three months ended March 31, 2016 (in thousands) As reported Pro forma Revenue $ 71,383 $ 71,383 Net loss $ (61,816 ) $ (31,759 )

Inventories, net

Inventories, net	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Inventories, net	Inventories, net Inventories, net are summarized as follows (in thousands): Successor September 30, 2017 December 31, 2016 Coal $ 12,691 $ 18,788 Raw materials, parts, supplies and other, net 21,211 20,632 Total inventories, net $ 33,902 $ 39,420

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the three and nine months ended September 30, 2017 (Successor), the Company estimated its annual effective tax rate based on projected financial income for the full year 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. The Company recognized an income tax benefit of $37.6 million and $2.9 million for the three and nine months ended September 30, 2017 (Successor), respectively. The Company recognized no income tax expense for the three and six months ended September 30, 2016 (Successor) and recognized income tax expense of $18.0 thousand for the three months ended March 31, 2016 (Predecessor). On March 31, 2016, the Company experienced an ownership change for purposes of Section 382 of the Internal Revenue Code of 1986, as amended (the "Code"). As a result of such ownership change, absent an applicable exception to such rules, an annual limitation, under Code Section 382 would apply, for federal and certain state income tax purposes, on the utilization of net operating loss carryforwards ("NOLs"). The Company had requested a private letter ruling ("PLR") from the Internal Revenue Service ("IRS") to clarify certain questions, that if the IRS ruled favorably on, would allow the Company to qualify for an exception to the aforementioned rules limiting its utilization of its NOLs. On September 18, 2017, the IRS issued such favorable PLR and, as such, the Company now believes it qualifies for an exception to such limitation rules. Prior to the issuance of the PLR, the Company operated and prepared its financial statements based on an assumption that the annual limitation on the utilization of the NOLs existed. Based on the receipt of the favorable PLR, the Company now believes that it qualifies for an exception to such NOL limitation rules and as such, no annual Code Section 382 limitation to the utilization of its federal NOLs applies. As a result of qualifying for such exception, the Company's federal and state NOLs were revised downward to approximately $1.8 to $2.0 billion as of September 30, 2017. Under the aforementioned exception to the Code Section 382 limitation, if the Company were to undergo a subsequent ownership change within two years of the Asset Acquisition, prior to April 1, 2018, its NOLs would effectively be reduced to zero. A subsequent ownership change could severely limit or eliminate the Company's ability to utilize its NOLs and other tax attributes. See "Part II, Item 1A. Risk Factors - We may be unable to generate sufficient taxable income from future operations, or other circumstances could arise, which may limit or eliminate our ability to utilize our significant tax NOLs or maintain our deferred tax assets" for additional discussion of this risk. In connection with the PLR, the Company made a year-to-date adjustment of $37.6 million , or $0.71 per share, in the third quarter of 2017 to reflect the change in application of Section 382 in computing income tax expense. The Company also recognized an income tax receivable of approximately $17.0 million , which represents the overpayment of estimated quarterly tax payments as a result of the change in estimated tax expense and refundable alternative minimum tax credits of approximately $9.7 million associated with capital expenditures. The Company records deferred tax assets to the extent these assets will more likely than not be realized. The Company provides a valuation allowance for deferred tax assets when it is more likely than not that some portion or all of its deferred tax assets, will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income. The Company considers all available positive and negative evidence, including scheduled reversals of deferred tax liabilities, projected future taxable income, tax planning strategies and recent financial performance in evaluating the realizability of its deferred tax assets. Many factors are considered which impact the Company's projections of future sustained profitability including risk associated with being a newly formed Company with a limited performance record and operating history on a standalone basis, our ability to successfully implement our business strategies and maximize profitable production and other conditions which are beyond the Company's control, such as the health of the global economy and the global steelmaking industry, the level and volatility of met coal prices and the hazards and operating risks involved with mining. The Company has concluded as of September 30, 2017 (Successor), that the valuation allowance was still needed on its deferred tax assets based on the weight of the factors describe above. If it is later determined that the Company will more likely than not realize all, or a portion, of the deferred tax assets, the Company will adjust the valuation allowance in a future period. If for the remainder of 2017, the Company is able to successfully implement its business strategy, maximize profitable production, continue to have positive operating results and projections for met coal pricing stabilize and remain strong, the Company may release all or a portion of its valuation allowance as early as the end of 2017, which could materially and favorably affect net income and stockholders' equity. Results of operations of the Predecessor have historically been included in the federal and state income tax returns of the Parent. Accordingly, the income tax provision included in the Predecessor financial statements was calculated using a method consistent with a separate return basis, as if the Predecessor had been a separate taxpayer. Similarly, historical tax attributes (net operating losses, alternative minimum tax credits, etc.) have been allocated to the Predecessor’s business utilizing a reasonable method of allocation.

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt On April 1, 2016, the Company entered into an Asset-Based Revolving Credit Agreement (the “ABL Facility”) with certain lenders and Citibank, N.A. (together with its affiliates, “Citibank”), as administrative agent and collateral agent, with an aggregate lender commitment to make a revolving loan of up to $50.0 million , subject to borrowing base availability. On January 23, 2017, the Company entered into Amendment No. 1 to the ABL Facility to, among other things, (i) increase the aggregate lender commitment to $100.0 million , (ii) reduce the applicable interest rate margins by 100 basis points ("bps"), (iii) permit the corporate conversion and (iv) allow the IPO to be consummated without triggering a change of control. On March 24, 2017, the Company entered into Amendment No. 2 to the ABL Facility to modify certain terms relating to the restricted payment covenant, which provides the Company with improved flexibility to pay dividends, including the Special Distribution. On May 15, 2017, the Company entered into Amendment No. 3 to the ABL Facility to, among other things, (i) allow for the posting of cash collateral to secure certain swap and hedging arrangements permitted under the ABL Facility and (ii) allow for the payment of dividends permitted under the ABL Facility within 60 days of declaration thereof. At September 30, 2017 (Successor), the Company had $100.0 million of availability under the ABL Facility. In connection with the Asset Acquisition, the Company assumed a security agreement and promissory note, which had an outstanding balance of $4.4 million as of September 30, 2017 (Successor), of which $2.9 million was classified as a current obligation. The amount owed in respect of the promissory note was originally used for the purchase of underground mining equipment and such note is secured by the same mining equipment. The promissory note matures on March 31, 2019 and bears a fixed interest rate of 4.00% per annum. The Company is required to make monthly payments of principal and interest during the term of the promissory note. See Note 16 for discussion of Amendment No. 4 to the ABL Facility entered into and the consummation of a private offering of $350.0 million aggregate principal amount of 8.00% Senior Secured Notes due 2024 subsequent to September 30, 2017.

Net Income (Loss) per Share

Net Income (Loss) per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Income (Loss) per Share	Net Income (Loss) per Share Basic and diluted net income (loss) per share was calculated as follows (in thousands, except per share data): Successor For the three For the nine months ended For the six months ended 2017 2016 2017 2016 Numerator: Net income (loss) $ 119,717 $ (33,642 ) $ 357,890 $ (83,705 ) Denominator: Weighted-average shares used to compute net income (loss) per share—basic and diluted 52,777 52,640 52,727 52,640 Net income (loss) per share—basic and diluted $ 2.27 $ (0.64 ) $ 6.79 $ (1.59 ) As of September 30, 2017 (Successor), there were 798,124 shares of common stock issued under our 2016 Equity Incentive Plan (the "2016 Equity Plan") to certain directors and employees, for which neither the performance nor market based vesting conditions were met as of the measurement date. As such, these common shares have been excluded from basic and diluted earnings per share. As of September 30, 2017 (Successor), there were 43,580 shares of our common stock contingently issuable upon the settlement of a vested phantom unit award under our 2016 Equity Plan and 13,157 shares of our common stock contingently issuable upon the settlement of a vested restricted stock unit award under our 2017 Equity Incentive Plan (the "2017 Equity Plan"). The settlement date is the earlier of a change in control as described in our 2016 Equity Plan and 2017 Equity Plan 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. As of September 30, 2017 (Successor), there were 17,582 shares of common stock issued under our 2017 Equity Plan to certain directors and employees. On March 31, 2017 (Successor), our board of managers declared a cash distribution of $3.56 per share, totaling $190.0 million , which was paid on March 31, 2017 to holders of our Class A Units, Class B Units and Class C Units of record as of March 27, 2017. On May 17, 2017, the board of directors of the Company (the "Board") adopted a policy (the "Dividend Policy") of paying a quarterly cash dividend of $0.05 per share. The initial quarterly dividend of $2.7 million was paid on June 13, 2017 to stockholders of record on May 30, 2017. The Dividend Policy also states the following: In addition to the regular quarterly dividend and to the extent that the Company generates excess cash that is beyond the then current requirements of the business, the Board may consider returning all or a portion of such excess cash to stockholders through a special dividend or implementation of a stock repurchase program. Any future dividends or stock repurchases will be at the discretion of the Board and subject to consideration of a number of factors, including business and market conditions, future financial performance and other strategic investment opportunities. The Company will also seek to optimize its capital structure to improve returns to stockholders while allowing flexibility for the Company to pursue very selective strategic growth opportunities that can provide compelling stockholder returns. On July 31, 2017, the Board declared a regular quarterly cash dividend of $0.05 per share, totaling $2.7 million , which was paid on August 23, 2017, to stockholders of record as of the close of business on August 14, 2017.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions In connection with the Asset Acquisition, the Company acquired 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 BWT 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 were $1.3 million and $0.5 million for the three and nine months ended September 30, 2017 (Successor), respectively, $1.3 million and $0.9 million for the three and six months ended September 30, 2016 (Successor), respectively, and $0.3 million for the three months ended March 31, 2016 (Predecessor). The Predecessor also received revenue from coal sales to affiliates of the Parent that were not acquired in connection with the Asset Acquisition. The Predecessor recognized revenue from these affiliates of $1.4 million for the three months ended March 31, 2016 (Predecessor).

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
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 that it is in substantial 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, 2017 (Successor) and December 31, 2016 (Successor), 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 a number of 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, 2017 (Successor) and December 31, 2016 (Successor), there were no items accrued for miscellaneous litigation. Indemnifications In the ordinary course of business, the Company entered into a contractual arrangement under which the Company has agreed to indemnify a third party to such arrangement from any losses arising from certain events as specified in the particular contracts, which may include, for example, litigation or claims relating to past performance. The Company had accrued $0.3 million as of September 30, 2017 (Successor) and December 31, 2016 (Successor), which is included in other long-term liabilities. The remaining maximum exposure under this arrangement is $0.2 million . 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, 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, 2017 (Successor), the Company had no liability recorded for minimum throughput requirements. At December 31, 2016 (Successor), the Company had accrued a liability of $2.1 million as a result of not meeting the required minimums, which is included in accrued expenses on the Condensed Balance Sheet. Royalty and Lease Obligations The Company’s leases are primarily for mining equipment and automobiles. At September 30, 2017 (Successor) and December 31, 2016 (Successor), the Company had no future minimum payments due under non-cancellable operating leases. 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 $22.3 million and $74.5 million , for the three and nine months ended September 30, 2017 (Successor), respectively, $2.7 million and $6.7 million for the three and six months ended September 30, 2016 (Successor), respectively, and $3.6 million for the three months ended March 31, 2016 (Predecessor).

Stockholders' Equity (Notes)

Stockholders' Equity (Notes)	9 Months Ended
	Sep. 30, 2017
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. As of September 30, 2017 , there were 53,446,284 shares of common stock issued and outstanding. On March 31, 2017, the board of managers declared a cash distribution payable to holders of our then outstanding Class A Units, Class B Units and Class C Units as of March 27, 2017, resulting in distributions to such holders in the aggregate amount of $ 190.0 million (the “Special Distribution”). In connection with the conversion of Warrior Met Coal, LLC into Warrior Met Coal, Inc., the Class C Units, which were issued pursuant to the 2016 Equity Plan, were converted into restricted shares (the "Restricted Shares") of common stock of the Company, par value $0.01 per share, and the Special Distribution with respect to such Restricted Shares was not paid but held in trust pending their vesting. As of September 30, 2017 (Successor), approximately $3.1 million is held in the trust and is included within other long term assets in the accompanying Condensed Balance Sheets. On June 1, 2017, the Compensation Committee (the "Committee") of the board of directors approved the modification described below (the “Modification”) to the award agreements (the “Awards”) for the Restricted Shares to certain officers, directors and employees of the Company. Pursuant to the Modification, the Committee waived certain vesting requirements with respect to the Special Distribution for the Restricted Shares such that funds currently held in trust as described above with respect to the Special Distribution will vest immediately for recipients that received less than $100.0 thousand and for recipients that received greater than $100.0 thousand , 50% of the Restricted Shares vest immediately. However, funds held in trust with respect to the Special Distribution for the remaining 50% of the Restricted Shares will not be released until such shares vest pursuant to the original terms of the Awards on the basis of the passage of time and the Company’s achievement of certain metrics. In addition and pursuant to the Modification, the holders of the Restricted Shares were permitted to elect to receive the 2017 Dividend released from trust as described above with respect to their Restricted Shares (i) 100% in cash; (ii) 50% in cash and 50% in restricted stock units (“RSUs”); or (iii) 100% in RSUs. In connection with the Modification, the Committee approved a form of Restricted Stock Unit Award Agreement (the “RSU Award Agreement”) pursuant to the 2017 Equity Plan on June 1, 2017 (the “Grant Date”) for those Holders who elected to receive the Special Distribution, in whole or in part, in RSUs (the “Participants”). The RSU Award Agreement provides that RSUs awarded pursuant to the Modification shall be fully vested on the Grant Date and shall be settled in shares of Common Stock on a one -for-one basis on the earliest of (i) one-third on each of the first three anniversaries of the Grant Date; (ii) a Change in Control (as defined in the Plan); (iii) the Participant’s separation from service with the Company or its affiliates; or (iv) death of the Participant. In connection with the Modification, for the nine months ended September 30, 2017 (Successor), the Company recognized a reduction to dividends payable of $0.2 million associated with the holders that elected to receive cash and $1.3 million was treated as an adjustment to equity for those that elected RSUs. Also, due to the Company's IPO, the Company recognized approximately $0.6 million of stock compensation expense for awards granted under the 2016 Equity Plan for the nine months ended September 30, 2017 . For the nine months ended September 30, 2017 (Successor), the Company also recognized approximately $0.5 million of compensation expense for awards granted under the 2017 Equity Plan.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The Company enters into natural gas swap contracts 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, 2017 (Successor), the Company had natural gas swap contracts outstanding with notional amounts totaling 1,980 million British thermal units maturing in the fourth quarter of 2017 and 2,400 million maturing in the fourth quarter of 2018. As of December 31, 2016 (Successor), the Company had natural gas swap contracts outstanding with notional amounts totaling 7,920 million British thermal units maturing in the fourth quarter of 2017. 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 an asset of $0.3 million related to natural gas swap contracts outstanding as of September 30, 2017 (Successor), of which $0.25 million was included in prepaid expenses and $0.05 million was included in other long-term assets, and $3.8 million as of December 31, 2016 (Successor) 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, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The following table presents information about the Company’s financial liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): Successor Fair Value Measurements as of September 30, 2017 Using: Level 1 Level 2 Level 3 Total Assets: Natural gas swap contracts $ — $ 288 $ — $ 288 Successor Fair Value Measurements as of December 31, 2016 Using: Level 1 Level 2 Level 3 Total Liabilities: Natural gas swap contracts $ — $ 3,784 $ — $ 3,784 The Company has no assets or any other liabilities measured at fair value on a recurring basis as of September 30, 2017 (Successor) or December 31, 2016 (Successor). During the three and nine months ended September 30, 2017 (Successor), there were no transfers between Level 1, Level 2 and Level 3. The Company uses quoted dealer prices for similar contracts in active over-the-counter markets for determining fair value of Level 2 liabilities. There were no changes to the valuation techniques used to measure liability fair values on a recurring basis during the three and nine months ended September 30, 2017 (Successor). 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 accounts payable— The carrying amounts reported in the Condensed Balance Sheet approximate fair value due to the short-term nature of these assets and liabilities. Debt— The Company's outstanding promissory note approximates fair value.

Reorganization Items, Net

Reorganization Items, Net	9 Months Ended
	Sep. 30, 2017
Reorganizations [Abstract]
Reorganization Items, Net	Reorganization Items, Net Expenses and income directly associated with the Chapter 11 Cases are reported separately in the Condensed Statements of Operations as reorganization items as required by ASC 852. Reorganization items also include adjustments to reflect the carrying value of liabilities subject to compromise at their estimated allowed claim amounts, as such adjustments are determined. Reorganization items include an allocation of professional fees incurred in relation to the Chapter 11 Cases. For the three months ended March 31, 2016 (Predecessor), the cost of these professional fees was allocated on the basis of the Predecessor’s assets as compared to the total assets of the Parent for each reporting period. The following table presents reorganization items (in thousands): Predecessor For the three months ended March 31, 2016 Professional fees (10,962 ) Rejected executory contracts, leases and other 18,882 Reorganization items, net $ 7,920 Net cash paid for reorganization items for the three months ended March 31, 2016 (Predecessor) totaled approximately $ 12.3 million .

Restructuring Costs

Restructuring Costs	9 Months Ended
	Sep. 30, 2017
Restructuring and Related Activities [Abstract]
Restructuring Costs	Restructuring Costs For the three months ended March 31, 2016 (Predecessor), the Predecessor recognized restructuring charges of approximately $ 3.4 million due to workforce reductions at the Alabama No. 7 underground mine, the Alabama No. 4 underground mine and corporate headquarters in conjunction with cost containment initiatives implemented in response to the deterioration in the metallurgical coal market. The restructuring charges consist primarily of severance and related benefits costs. The Company does not expect to incur any additional restructuring charges in the Successor periods in connection with the Predecessor restructuring actions.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
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, other post-retirement benefits, transactions costs, restructuring costs, interest expense, reorganization items, net and income tax expense by segment. The following tables include reconciliations of segment information to consolidated amounts (in thousands): Successor Predecessor For the three For the nine months ended September 30, For the six For the three 2017 2016 2017 2016 2016 Revenues Mining $ 302,958 $ 44,395 $ 895,802 $ 129,810 $ 65,154 All other 8,997 8,496 33,487 14,555 6,229 Total revenues $ 311,955 $ 52,891 $ 929,289 $ 144,365 $ 71,383 Successor Predecessor For the three For the nine months ended September 30, For the six For the three 2017 2016 2017 2016 2016 Capital Expenditures Mining 34,125 $ 2,081 $ 60,647 $ 7,424 $ 4,588 All other 283 354 2,024 1,025 834 Total capital expenditures 34,408 $ 2,435 $ 62,671 $ 8,449 $ 5,422 The Company evaluates the performance of its segment based on Segment Adjusted EBITDA, which is defined as net income (loss) adjusted for other revenues, cost of other revenues, depreciation and depletion, selling, general and administrative, other postretirement benefits, 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 (loss), which is its most directly comparable financial measure calculated and presented in accordance with GAAP (in thousands): Successor Predecessor For the three For the nine months ended September 30, For the six For the three 2017 2016 2017 2016 2016 Segment Adjusted EBITDA $ 113,394 $ (7,392 ) $ 439,942 $ (25,843 ) $ (7,143 ) Other revenues 8,997 8,496 33,487 14,555 6,229 Cost of other revenues (6,985 ) (6,998 ) (22,959 ) (12,124 ) (4,698 ) Depreciation and depletion (23,393 ) (22,538 ) (57,625 ) (38,359 ) (28,958 ) Selling, general and administrative (9,243 ) (4,516 ) (23,073 ) (10,331 ) (9,008 ) Other postretirement benefits — — — — (6,160 ) Restructuring charges — — — — (3,418 ) Transaction and other costs — — (12,873 ) (10,475 ) — Interest expense, net (640 ) (694 ) (1,890 ) (1,128 ) (16,562 ) Reorganization items, net — — — — 7,920 Income tax benefit (expense) 37,587 — 2,881 — (18 ) Net income (loss) $ 119,717 $ (33,642 ) $ 357,890 $ (83,705 ) $ (61,816 )

Subsequent Events (Notes)

Subsequent Events (Notes)	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Amendment to ABL Facility On October 3, 2017, the Company entered into Amendment No. 4 to the ABL Facility and Amendment No. 2 to the Pledge and Security Agreement dated as of April 1, 2016 (the “Security Agreement”) (the "Fourth Amendment") to, among other things, (i) provide an exception to the indebtedness and lien negative covenants in the ABL Facility to permit the Company to incur indebtedness in an aggregate principal amount not to exceed $500.0 million at any time outstanding, which indebtedness may be unsecured or secured and (ii) to amend certain provisions in the Security Agreement to reflect additional lien and indebtedness capacity granted under the ABL Facility as amended by the Fourth Amendment. Regular Quarterly Dividend On October 25, 2017, the Board declared a regular quarterly cash dividend of $0.05 per share, totaling $2.7 million , which will be paid on November 10, 2017, to stockholders of record as of the close of business on November 3, 2017. Senior Secured Notes Offering and November Special Dividend On November 2, 2017, the Company consummated a private offering (the “Offering”) of $350.0 million aggregate principal amount of 8.00% Senior Secured Notes due 2024 (the “Notes”) to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”), and to certain non-U.S. persons in transactions outside the United States in accordance with Regulation S under the Securities Act. The Company will use the net proceeds of approximately $340.0 million from the Offering, together with cash on hand of approximately $260.0 million , to pay a special cash dividend of approximately $600.0 million , or $11.21 per share, to all of its stockholders on a pro rata basis (the "November Special Dividend"). On November 2, 2017, the Board declared the November Special Dividend to be paid on November 22, 2017 to stockholders of record as of the close of business on November 13, 2017. The Notes will mature on November 1, 2024 and interest is payable on May 1 and November 1 of each year, commencing May 1, 2018. The Notes are fully and unconditionally guaranteed on a joint and several basis by each of the Company's direct and indirect wholly-owned domestic restricted subsidiaries that are guarantors under the ABL Facility (subject to customary release provisions). At any time prior to November 1, 2020, the Company may redeem the Notes, in whole or in part, at a price equal to 100.00% of the principal amount of the Notes redeemed plus the Applicable Premium (as defined in the indenture governing the Notes) and accrued and unpaid interest, if any, to, but excluding, the applicable redemption date. The Notes are redeemable at the Company's option, in whole or in part, from time to time, on or after November 1, 2020, at redemption prices specified in the indenture, plus accrued and unpaid interest, if any, to, but excluding the redemption date. At any time on or prior to November 1, 2020, the Company may redeem up to 40% of the aggregate principal amount of the Notes with the proceeds of certain equity offerings, at a redemption price of 108.00% of the principal amount of the Notes, plus accrued and unpaid interest, if any, to but excluding the redemption date. The Company is also required to make offers to purchase the Notes (i) at a purchase price of 101.00% of the principal amount thereof in the event it experiences specific kinds of change of control triggering events, (ii) at a purchase price of 103.00% of the principal amount thereof prior to making certain restricted payments, and (iii) at a purchase price of 100.00% of the principal amount there of in the event it makes certain asset sales or dispositions and does not reinvest the net proceeds therefrom or use such net proceeds to repay certain indebtedness, in each case, plus accrued and unpaid interest, if any, to, but excluding the date of purchase.

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying financial statements have been presented on a condensed consolidated basis for the “Successor” periods subsequent to the Asset Acquisition, which include the three and nine months ended September 30, 2017 , the three and six months ended September 30, 2016 and on a condensed combined basis for the “Predecessor” periods prior to the Asset Acquisition, which includes the three months ended March 31, 2016. The financial information of the Company has been separated by a vertical line on the face of the financial statements to identify these different bases of accounting for Predecessor and Successor periods. 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, 2017 (Successor) and December 31, 2016 (Successor), restricted cash included in other long-term assets in the Condensed Balance Sheet represents amounts funded to an escrow account as collateral for coal royalties due under certain underground coal mining lease contracts.
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 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. Securities classified as held to maturity securities are those securities that management has the intent and ability to hold to maturity.
New Accounting Pronouncements	In September 2015, the FASB issued Accounting Standards Update ("ASU") 2015-16, “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments,” which eliminates the requirement that an acquirer in a business combination account for measurement-period adjustments retrospectively. Instead, an acquirer will recognize a measurement-period adjustment during the period in which it determines the amount of the adjustment. The guidance is effective for public business entities for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. We adopted the amendments of ASU 2015-16, effective January 1, 2017. We recognized a $3.5 million measurement-period adjustment during the three months ended March 31, 2017 (Successor), which we reflected prospectively (see Note 3). In May 2014, the FASB issued ASU 2014-09 “Revenue from Contracts with Customers”. The new standard requires an entity to recognize revenue upon transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance also requires additional disclosures about the nature, amount, timing, and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date,” which defers the effective date of ASU 2014-09 by one year. ASU 2015-09 is effective for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period and permits early adoption on a limited basis. The Company plans to adopt ASU 2014-09 as of January 1, 2018, using the modified retrospective approach. Based on the current status of the Company’s assessment of the new standard, the Company does not anticipate any significant changes to the current timing or method for recognizing revenue. Additionally, the Company does not anticipate the new standard to have a material impact on our financial statements outside of the expanded disclosure requirements.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2017
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): Successor September 30, 2017 December 31, 2016 Cash and cash equivalents $ 234,053 $ 150,045 Restricted cash included in other long-term assets 1,354 2,611 Total cash and cash equivalents and restricted cash included in the Statements of Cash Flows $ 235,407 $ 152,656
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): Successor September 30, 2017 December 31, 2016 Cash and cash equivalents $ 234,053 $ 150,045 Restricted cash included in other long-term assets 1,354 2,611 Total cash and cash equivalents and restricted cash included in the Statements of Cash Flows $ 235,407 $ 152,656

Acquisition of the Predecessor

Acquisition of the Predecessor (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of Acquisition of the Predecessor	The following tables summarize the final purchase price allocation, including the applicable measurement-period adjustments made upon finalization during the first quarter of 2017 (in thousands): Final purchase price: Cash paid $ 50,830 Fair value of First Lien Obligations relinquished in exchange for net assets of the Predecessor 598,607 Total purchase price $ 649,437 Final fair values of assets acquired and liabilities assumed: Cash and cash equivalents $ 26,723 Trade and other receivables 14,358 Inventories 46,464 Prepaid expenses and other current assets 30,722 Mineral interests 144,224 Property, plant and equipment 533,441 Other long-term assets 28,865 Total assets 824,797 Accounts payable 10,470 Accrued expenses 12,843 Other current liabilities 24,044 Current debt 2,879 Long-term debt 5,758 Deferred income taxes 1,400 Other long-term liabilities 117,966 Total liabilities 175,360 Total fair value of net assets acquired $ 649,437
Supplemental Unaudited Pro Forma Financial Information	The following unaudited pro forma results of operations give effect to the Asset Acquisition as if it had occurred on January 1, 2015. This unaudited pro forma financial information should not be relied upon as necessarily being indicative of the historical results that would have been obtained if the Asset Acquisition had actually occurred on that date, nor the results of operations in the future. The 2016 supplemental unaudited pro forma financial information was adjusted to (i) reflect the impact of certain fair value adjustments, including an adjustment to depreciation and depletion expense as a result of a change in the basis of Property, Plant and Equipment and Mineral Interests, (ii) eliminate historical interest expense related to the notes, loans and other debt that was not assumed by the Company as part of the Asset Acquisition, (iii) eliminate a gain on reorganization items associated with the Chapter 11 Cases and (iv) eliminate the Predecessor's historical other postretirement benefit expense associated with the Predecessor's historical other postretirement benefit obligations for retiree medical and life insurance benefits, which were not assumed by the Company. Predecessor For the three months ended March 31, 2016 (in thousands) As reported Pro forma Revenue $ 71,383 $ 71,383 Net loss $ (61,816 ) $ (31,759 )

Inventories, net (Tables)

Inventories, net (Tables)	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Schedule of Inventories, Net	Inventories, net are summarized as follows (in thousands): Successor September 30, 2017 December 31, 2016 Coal $ 12,691 $ 18,788 Raw materials, parts, supplies and other, net 21,211 20,632 Total inventories, net $ 33,902 $ 39,420

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Basic and diluted net income (loss) per share was calculated as follows (in thousands, except per share data): Successor For the three For the nine months ended For the six months ended 2017 2016 2017 2016 Numerator: Net income (loss) $ 119,717 $ (33,642 ) $ 357,890 $ (83,705 ) Denominator: Weighted-average shares used to compute net income (loss) per share—basic and diluted 52,777 52,640 52,727 52,640 Net income (loss) per share—basic and diluted $ 2.27 $ (0.64 ) $ 6.79 $ (1.59 )

Fair Value of Financial Instr29

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
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 and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): Successor Fair Value Measurements as of September 30, 2017 Using: Level 1 Level 2 Level 3 Total Assets: Natural gas swap contracts $ — $ 288 $ — $ 288 Successor Fair Value Measurements as of December 31, 2016 Using: Level 1 Level 2 Level 3 Total Liabilities: Natural gas swap contracts $ — $ 3,784 $ — $ 3,784

Reorganization Items, Net (Tabl

Reorganization Items, Net (Tables)	9 Months Ended
	Sep. 30, 2017
Reorganizations [Abstract]
Schedule of Reorganization Items	The following table presents reorganization items (in thousands): Predecessor For the three months ended March 31, 2016 Professional fees (10,962 ) Rejected executory contracts, leases and other 18,882 Reorganization items, net $ 7,920

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Reconciliation of Revenue from Segments to Consolidated	The following tables include reconciliations of segment information to consolidated amounts (in thousands): Successor Predecessor For the three For the nine months ended September 30, For the six For the three 2017 2016 2017 2016 2016 Revenues Mining $ 302,958 $ 44,395 $ 895,802 $ 129,810 $ 65,154 All other 8,997 8,496 33,487 14,555 6,229 Total revenues $ 311,955 $ 52,891 $ 929,289 $ 144,365 $ 71,383
Reconciliation of Capital Expenditures from Segments to Consolidated	Successor Predecessor For the three For the nine months ended September 30, For the six For the three 2017 2016 2017 2016 2016 Capital Expenditures Mining 34,125 $ 2,081 $ 60,647 $ 7,424 $ 4,588 All other 283 354 2,024 1,025 834 Total capital expenditures 34,408 $ 2,435 $ 62,671 $ 8,449 $ 5,422
Reconciliation of Net Income (Loss) from Segments to Consolidated	Below is a reconciliation of Segment Adjusted EBITDA to net income (loss), which is its most directly comparable financial measure calculated and presented in accordance with GAAP (in thousands): Successor Predecessor For the three For the nine months ended September 30, For the six For the three 2017 2016 2017 2016 2016 Segment Adjusted EBITDA $ 113,394 $ (7,392 ) $ 439,942 $ (25,843 ) $ (7,143 ) Other revenues 8,997 8,496 33,487 14,555 6,229 Cost of other revenues (6,985 ) (6,998 ) (22,959 ) (12,124 ) (4,698 ) Depreciation and depletion (23,393 ) (22,538 ) (57,625 ) (38,359 ) (28,958 ) Selling, general and administrative (9,243 ) (4,516 ) (23,073 ) (10,331 ) (9,008 ) Other postretirement benefits — — — — (6,160 ) Restructuring charges — — — — (3,418 ) Transaction and other costs — — (12,873 ) (10,475 ) — Interest expense, net (640 ) (694 ) (1,890 ) (1,128 ) (16,562 ) Reorganization items, net — — — — 7,920 Income tax benefit (expense) 37,587 — 2,881 — (18 ) Net income (loss) $ 119,717 $ (33,642 ) $ 357,890 $ (83,705 ) $ (61,816 )

Business and Basis of Present32

Business and Basis of Presentation - Description of the Business (Details) - USD ($) $ in Billions	Nov. 05, 2015	Apr. 01, 2011
Predecessor
Business Acquisition [Line Items]
Credit bid to acquire business	$ 1.1
Walter Energy, Inc. | Senior Secured Notes | Senior Secured Notes due 2019
Business Acquisition [Line Items]
Stated interest rate		9.50%

Business and Basis of Present33

Business and Basis of Presentation - Special Distribution, Corporate Conversion and Initial Public Offering (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 19, 2017	Mar. 31, 2017	Sep. 30, 2017	Apr. 12, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Cash distributions paid		$ 190
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
Common stock shares outstanding (in shares)			53,446,284		53,442,532
Common Stock | IPO
Class of Stock [Line Items]
Stock issued during period (in shares)	16,666,667
Shares issued (in dollars per share)	$ 19
Proceeds from issuance of common stock	$ 296.9
Stock issuance costs	19.8
Payments of stock issuance costs	$ 15.9
Common stock shares outstanding (in shares)	53,442,532

Business and Basis of Present34

Business and Basis of Presentation - Predecessor Presentation (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)
Predecessor
Business Acquisition [Line Items]
Allocated costs	$ 7.8

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Cash and Cash Equivalents and Restricted Cash (Details) - Successor - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 234,053		$ 150,045
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash included in other long-term assets	1,354		2,611
Total cash and cash equivalents and restricted cash included in the Statements of Cash Flows	$ 235,407	$ 157,146	$ 152,656	$ 144,395	$ 131,602	$ 0

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Short-term Investments (Details) - Successor - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments	$ 17,501	$ 17,501
Treasury bills
Schedule of Held-to-maturity Securities [Line Items]
Short-term investments	$ 17,500	$ 17,500
Maturity term for short-term investments	6 months	6 months

Summary of Significant Accoun37

Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - Predecessor $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Business Acquisition [Line Items]
Decrease in fair value of mineral interests	$ 3.5
Decrease to additional paid in capital	$ 3.5

Acquisition of the Predecesso38

Acquisition of the Predecessor - Narrative (Details) - Predecessor - USD ($) $ in Thousands	Nov. 05, 2015	Mar. 31, 2017
Business Acquisition [Line Items]
Cash paid	$ 50,830
Net cash paid in acquisition	24,100
Cash acquired from acquisition	$ 26,700
Decrease in fair value of mineral interests		$ 3,500
Decrease to additional paid in capital		$ 3,500

Acquisition of the Predecesso39

Acquisition of the Predecessor - Schedule of Business Acquisition (Details) - Predecessor $ in Thousands	Nov. 05, 2015USD ($)
Final purchase price:
Cash paid	$ 50,830
Fair value of First Lien Obligations relinquished in exchange for net assets of the Predecessor	598,607
Total purchase price	649,437
Final fair values of assets acquired and liabilities assumed:
Cash and cash equivalents	26,723
Trade and other receivables	14,358
Inventories	46,464
Prepaid expenses and other current assets	30,722
Mineral interests	144,224
Property, plant and equipment	533,441
Other long-term assets	28,865
Total assets	824,797
Accounts payable	10,470
Accrued expenses	12,843
Other current liabilities	24,044
Current debt	2,879
Long-term debt	5,758
Deferred income taxes	1,400
Other long-term liabilities	117,966
Total liabilities	175,360
Total fair value of net assets acquired	$ 649,437

Acquisition of the Predecesso40

Acquisition of the Predecessor - Supplemental Unaudited Pro Forma Financial Information (Details) - Predecessor $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)
Business Acquisition [Line Items]
Revenue	$ 71,383
Net loss	(61,816)
Predecessor
Business Acquisition [Line Items]
Revenue - Pro forma	71,383
Net loss - Pro forma	$ (31,759)

Inventories, net (Details)

Inventories, net (Details) - Successor - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Inventory [Line Items]
Coal	$ 12,691	$ 18,788
Raw materials, parts, supplies and other, net	21,211	20,632
Total inventories, net	$ 33,902	$ 39,420

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017
Income Tax Disclosure [Line Items]
Tax expense (benefit) adjustment	$ (37,600,000)
Income tax receivable	17,000,000				$ 17,000,000
Refundable alternative minimum tax credits	(9,700,000)				(9,700,000)
Successor
Income Tax Disclosure [Line Items]
Income tax (benefit) expense	$ (37,587,000)	$ 0		$ 0	(2,881,000)
Tax expense (benefit) adjustment (in dollars per share)	$ 0.71
Predecessor
Income Tax Disclosure [Line Items]
Income tax (benefit) expense			$ 18,000
Minimum
Income Tax Disclosure [Line Items]
Federal NOLs	$ 1,800,000,000				1,800,000,000
Maximum
Income Tax Disclosure [Line Items]
Federal NOLs	$ 2,000,000,000				$ 2,000,000,000

Debt - ABL Facility (Details)

Debt - ABL Facility (Details) - USD ($)	Jan. 23, 2017	Nov. 02, 2017	Oct. 03, 2017	Sep. 30, 2017	Apr. 01, 2016
Citibank | Revolving Credit Agreement
Line of Credit Facility [Line Items]
Aggregate lender commitment	$ 100,000,000				$ 50,000,000
Interest rate margins	100.00%
Citibank | Revolving Credit Agreement | Successor
Line of Credit Facility [Line Items]
Remaining borrowing capacity				$ 100,000,000
Subsequent Event | Citibank | Revolving Credit Agreement
Line of Credit Facility [Line Items]
Aggregate lender commitment			$ 500,000,000
Subsequent Event | Senior Notes | Senior Secured Notes Due 2024
Line of Credit Facility [Line Items]
Aggregate lender commitment		$ 350,000,000
Stated interest rate		8.00%

Debt - Promissory Note (Details

Debt - Promissory Note (Details) - Successor - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Current portion of long-term debt	$ 2,936	$ 2,849
Senior Secured Notes
Debt Instrument [Line Items]
Long-term debt	4,400
Current portion of long-term debt	$ 2,900
Stated interest rate	4.00%

Net Income (Loss) per Share - S

Net Income (Loss) per Share - Schedule of Earnings per Share (Details) - Successor - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017
Numerator:
Net income (loss)	$ 119,717	$ (33,642)	$ (83,705)	$ 357,890
Denominator:
Weighted average number of shares outstanding—basic and diluted (in shares)	52,777	52,640	52,640	52,727
Net income (loss) per share—basic and diluted (in dollars per share)	$ 2.27	$ (0.64)	$ (1.59)	$ 6.79

Net Income (Loss) per Share - N

Net Income (Loss) per Share - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 31, 2017	Jun. 13, 2017	May 17, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
Class of Stock [Line Items]
Dividends paid (in dollars per share)			$ 0.05	$ 3.56
Dividends paid		$ 2,700		$ 190,000	$ 2,677	$ 0	$ 0	$ 195,350
Cash dividends	$ 2,700
Restricted Stock | 2016 Equity Plan | Successor
Class of Stock [Line Items]
Common stock issues to employees and directors, unvested (in shares)					798,124			798,124
Restricted Stock | 2017 Equity Plan | Successor
Class of Stock [Line Items]
Common stock issues to employees and directors, unvested (in shares)					17,582			17,582
Phantom Share Units (PSUs) | 2016 Equity Plan
Class of Stock [Line Items]
Settlement period								5 years
Phantom Share Units (PSUs) | 2016 Equity Plan | Successor
Class of Stock [Line Items]
Common stock shares issued (in shares)								43,580
Phantom Share Units (PSUs) | 2017 Equity Plan
Class of Stock [Line Items]
Settlement period								5 years
Restricted Stock Units (RSUs) | 2017 Equity Plan | Successor
Class of Stock [Line Items]
Common stock shares issued (in shares)								13,157

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Nov. 05, 2015
Predecessor | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from related parties			$ 1.4
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 | Successor | Corporate Joint Venture
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 1.3	$ 1.3		$ 0.5	$ 0.9
Allocated Expenses to Joint Venture | Predecessor | Corporate Joint Venture
Related Party Transaction [Line Items]
Expenses from transactions with related party			$ 0.3

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Successor
Guarantor Obligations [Line Items]
Throughput obligation	$ 0				$ 0
Future minimum operating lease payments	0				0	$ 0
Coal royalty expense	22,300,000	$ 2,700,000		$ 6,700,000	74,500,000
Successor | Indemnifications
Guarantor Obligations [Line Items]
Remaining maximum exposure	200,000				200,000
Successor | Other long-term liabilities | Indemnifications
Guarantor Obligations [Line Items]
Indemnification accrual	$ 300,000				$ 300,000	300,000
Successor | Accrued expenses
Guarantor Obligations [Line Items]
Throughput obligation						$ 2,100,000
Predecessor
Guarantor Obligations [Line Items]
Coal royalty expense			$ 3,600,000

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($)	Jun. 13, 2017	Jun. 01, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017	Apr. 12, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common stock shares authorized (in shares)				140,000,000			140,000,000	140,000,000	140,000,000
Common stock par value (in dollars per share)				$ 0.01			$ 0.01	$ 0.01	$ 0.01
Preferred stock shares authorized (in shares)				10,000,000			10,000,000	10,000,000	10,000,000
Preferred stock par value (in dollars per share)				$ 0.01			$ 0.01	$ 0.01	$ 0.01
Common stock shares issued (in shares)				53,446,284			53,446,284		53,442,532
Common stock shares outstanding (in shares)				53,446,284			53,446,284		53,442,532
Cash distributions paid			$ 190,000,000
Conversion ratio		1
Restricted Stock
Class of Stock [Line Items]
Common stock par value (in dollars per share)								$ 0.01
Successor
Class of Stock [Line Items]
Assets held in trust				$ 3,100,000			$ 3,100,000
Reduction to dividends payable	$ 2,700,000		$ 190,000,000	$ 2,677,000	$ 0	$ 0	195,350,000
Equity award modification							1,255,000
2016 Equity Plan Modification | Successor
Class of Stock [Line Items]
Reduction to dividends payable							200,000
Equity award modification							1,300,000
2016 Equity Plan | Successor
Class of Stock [Line Items]
Stock compensation expense							600,000
2017 Equity Plan | Successor
Class of Stock [Line Items]
Stock compensation expense							$ 500,000
Less than 100k, Immediate Vesting | 2016 Equity Plan Modification
Class of Stock [Line Items]
Vested amount		$ 100,000
Greater than 100k, 50% Immediate Vesting and 50% Original Vesting Terms | 2016 Equity Plan Modification
Class of Stock [Line Items]
Vested amount		$ 100,000
Vested percentage		50.00%
100% Cash Award
Class of Stock [Line Items]
Percentage of dividends in cash		100.00%
50% Cash and 50% Equity Award
Class of Stock [Line Items]
Percentage of dividends in cash		50.00%
Restricted Stock Units (RSUs) | 50% Cash and 50% Equity Award
Class of Stock [Line Items]
Percentage of dividends in shares		50.00%
Restricted Stock Units (RSUs) | 100% Equity Award
Class of Stock [Line Items]
Percentage of dividends in shares		100.00%

Derivative Instruments (Details

Derivative Instruments (Details) - Successor - Not Designated as Hedging Instrument - Natural gas swap contracts $ in Thousands, BTU in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017USD ($)BTU	Dec. 31, 2016USD ($)BTU
Commodity Contract, Maturity Q4 2017
Derivative [Line Items]
Derivative energy measure (in BTUs) | BTU	1,980	7,920
Commodity Contract, Maturity Q4 2018
Derivative [Line Items]
Derivative energy measure (in BTUs) | BTU	2,400
Commodity Contract
Derivative [Line Items]
Natural gas swap contracts, asset	$ 300
Natural gas swap contracts, current asset	250
Natural gas swap contracts, noncurrent asset	$ 50
Natural gas swap contracts, current liability		$ 3,800

Fair Value of Financial Instr51

Fair Value of Financial Instruments (Details) - Successor - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 0	$ 0
Fair Value, Measurements, Recurring | Commodity Contract | Natural gas swap contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	288,000
Derivative liabilities		3,784,000
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]
Derivative assets	0
Derivative liabilities		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]
Derivative assets	288,000
Derivative liabilities		3,784,000
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]
Derivative assets	$ 0
Derivative liabilities		$ 0

Reorganization Items, Net (Deta

Reorganization Items, Net (Details) - Predecessor $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)
Schedule of Reorganization Items [Line Items]
Professional fees	$ (10,962)
Rejected executory contracts, leases and other	18,882
Reorganization items, net	7,920
Payments for reorganization items	$ 12,300

Restructuring Costs (Details)

Restructuring Costs (Details) - Predecessor $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 3,418
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 3,400

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2017segment
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			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
Segment Reporting Information [Line Items]
Mining revenue	$ 302,958	$ 44,395		$ 129,810	$ 895,802
Other revenues	8,997	8,496		14,555	33,487
Revenues	311,955	52,891		144,365	929,289
Successor | Segment Reconciling Items
Segment Reporting Information [Line Items]
Other revenues	8,997	8,496		14,555	33,487
Predecessor
Segment Reporting Information [Line Items]
Mining revenue			$ 65,154
Other revenues			6,229
Revenues			71,383
Predecessor | Segment Reconciling Items
Segment Reporting Information [Line Items]
Other revenues			6,229
Mining | Successor | Operating Segments
Segment Reporting Information [Line Items]
Mining revenue	$ 302,958	$ 44,395		$ 129,810	$ 895,802
Mining | Predecessor | Operating Segments
Segment Reporting Information [Line Items]
Mining revenue			$ 65,154

Segment Information - Reconci56

Segment Information - Reconciliation of Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
Segment Reporting Information [Line Items]
Capital Expenditures	$ 34,408	$ 2,435		$ 8,449	$ 62,671
Successor | Segment Reconciling Items
Segment Reporting Information [Line Items]
Capital Expenditures	283	354		1,025	2,024
Predecessor
Segment Reporting Information [Line Items]
Capital Expenditures			$ 5,422
Predecessor | Segment Reconciling Items
Segment Reporting Information [Line Items]
Capital Expenditures			834
Mining | Successor | Operating Segments
Segment Reporting Information [Line Items]
Capital Expenditures	$ 34,125	$ 2,081		$ 7,424	$ 60,647
Mining | Predecessor | Operating Segments
Segment Reporting Information [Line Items]
Capital Expenditures			$ 4,588

Segment Information - Reconci57

Segment Information - Reconciliation of Net Income (Loss) (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2017
Successor
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	$ 113,394,000	$ (7,392,000)		$ (25,843,000)	$ 439,942,000
Other revenues	8,997,000	8,496,000		14,555,000	33,487,000
Cost of other revenues	(6,985,000)	(6,998,000)		(12,124,000)	(22,959,000)
Depreciation and depletion	(23,393,000)	(22,538,000)		(38,359,000)	(57,625,000)
Selling, general and administrative	(9,243,000)	(4,516,000)		(10,331,000)	(23,073,000)
Other postretirement benefits	0	0		0	0
Restructuring charges	0	0		0	0
Transaction and other costs	0	0		(10,475,000)	(12,873,000)
Interest (expense), net	(640,000)	(694,000)		(1,128,000)	(1,890,000)
Reorganization items, net	0	0		0	0
Income tax benefit (expense)	37,587,000	0		0	2,881,000
Net income (loss)	$ 119,717,000	$ (33,642,000)		$ (83,705,000)	$ 357,890,000
Predecessor
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA			$ (7,143,000)
Other revenues			6,229,000
Cost of other revenues			(4,698,000)
Depreciation and depletion			(28,958,000)
Selling, general and administrative			(9,008,000)
Other postretirement benefits			(6,160,000)
Restructuring charges			(3,418,000)
Transaction and other costs			0
Interest (expense), net			(16,562,000)
Reorganization items, net			7,920,000
Income tax benefit (expense)			(18,000)
Net income (loss)			$ (61,816,000)

Subsequent Events (Details)

Subsequent Events (Details) - USD ($)	Nov. 02, 2017	Oct. 25, 2017	Jul. 31, 2017	May 17, 2017	Mar. 31, 2017	Oct. 03, 2017	Jan. 23, 2017	Apr. 01, 2016
Subsequent Event
Subsequent Event [Line Items]
Dividends declared (in dollars per share)		$ 0.05
Cash on hand to pay dividend	$ 260,000,000
Citibank | Revolving Credit Agreement
Subsequent Event [Line Items]
Maximum borrowing capacity							$ 100,000,000	$ 50,000,000
Citibank | Revolving Credit Agreement | Subsequent Event
Subsequent Event [Line Items]
Maximum borrowing capacity						$ 500,000,000
Senior Secured Notes Due 2024 | Senior Notes | Subsequent Event
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 350,000,000
Dividends declared (in dollars per share)	$ 11.21
Cash dividends	$ 600,000,000
Stated interest rate	8.00%
Net proceeds from debt	$ 340,000,000
Successor
Subsequent Event [Line Items]
Dividends declared (in dollars per share)				$ 0.05	$ 3.56
Cash dividends			$ 2,700,000
Successor | Subsequent Event
Subsequent Event [Line Items]
Cash dividends		$ 2,700,000
Anytime prior to November 1, 2020 | Senior Secured Notes Due 2024 | Subsequent Event
Subsequent Event [Line Items]
Redemption price, percentage	100.00%
Anytime prior to November 1, 2020 | Senior Secured Notes Due 2024, Partial Redemption | Subsequent Event
Subsequent Event [Line Items]
Redemption price, percentage	108.00%
Percentage of aggregate principal amount redeemable	40.00%
Upon occurrence of a change in control | Senior Secured Notes Due 2024 | Subsequent Event
Subsequent Event [Line Items]
Redemption price, percentage	101.00%
Prior to making certain restricted payments | Senior Secured Notes Due 2024 | Subsequent Event
Subsequent Event [Line Items]
Redemption price, percentage	103.00%
Upon occurrence of asset sales or dispositions | Senior Secured Notes Due 2024 | Subsequent Event
Subsequent Event [Line Items]
Redemption price, percentage	100.00%