Alliance Resource Partners (ARLP) 10-K20 Feb 202019 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Feb. 20, 2020	Jun. 28, 2019
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2019
Entity File Number	0-26823
Entity Registrant Name	ALLIANCE RESOURCE PARTNERS LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	73-1564280
Entity Address, Address Line One	1717 South Boulder Avenue, Suite 400
Entity Address, City or Town	Tulsa
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	74119
City Area Code	918
Local Phone Number	295-7600
Title of 12(b) Security	Common Units
Trading Symbol	ARLP
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Units Outstanding		127,195,219
Entity Public Float			$ 1,809,240,225
Entity Central Index Key	0001086600
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 36,482	$ 244,150
Trade receivables	161,679	174,914
Other receivables	256	395
Inventories, net	101,305	59,206
Advance royalties	1,844	1,274
Prepaid expenses and other assets	18,019	20,747
Total current assets	319,585	500,686
PROPERTY, PLANT AND EQUIPMENT:
Property, plant and equipment, at cost	3,684,008	2,925,808
Less accumulated depreciation, depletion and amortization	(1,675,022)	(1,513,450)
Total property, plant and equipment, net	2,008,986	1,412,358
OTHER ASSETS:
Advance royalties	52,057	42,923
Equity method investments	28,529	161,309
Equity securities		122,094
Goodwill	136,399	136,399
Operating lease right-of-use assets	17,660
Other long-term assets	23,478	18,979
Total other assets	258,123	481,704
TOTAL ASSETS	2,586,694	2,394,748
CURRENT LIABILITIES:
Accounts payable	80,566	96,397
Accrued taxes other than income taxes	15,768	16,762
Accrued payroll and related expenses	36,575	43,113
Accrued interest	5,664	5,022
Workers' compensation and pneumoconiosis benefits	11,175	11,137
Current finance lease obligations	8,368	46,722
Current operating lease obligations	3,251
Other current liabilities	21,062	19,718
Current maturities, long-term debt, net	13,157	92,000
Total current liabilities	195,586	330,871
LONG-TERM LIABILITIES:
Long-term debt, excluding current maturities, net	768,194	564,004
Pneumoconiosis benefits	94,389	68,828
Accrued pension benefit	44,858	43,135
Workers' compensation	45,503	41,669
Asset retirement obligations	133,018	127,655
Long-term finance lease obligations	2,224	10,595
Long-term operating lease obligations	14,316
Other liabilities	23,182	20,304
Total long-term liabilities	1,125,684	876,190
Total liabilities	1,321,270	1,207,061
ARLP Partners' Capital:
Limited Partners - Common Unitholders 126,915,597 and 128,095,511 units outstanding, respectively	1,331,482	1,229,268
Accumulated other comprehensive loss	(77,993)	(46,871)
Total ARLP Partners' Capital	1,253,489	1,182,397
Noncontrolling interest	11,935	5,290
Total Partners' Capital	1,265,424	1,187,687
TOTAL LIABILITIES AND PARTNERS' CAPITAL	$ 2,586,694	$ 2,394,748

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED BALANCE SHEETS
Common units outstanding	126,915,597	128,095,511

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SALES AND OPERATING REVENUES:
Revenues	$ 1,961,720	$ 2,002,857	$ 1,796,220
EXPENSES:
Operating expenses (excluding depreciation, depletion and amortization)	1,182,100	1,207,713	1,091,855
Outside coal purchases	23,357	1,466
General and administrative	72,997	68,298	61,760
Depreciation, depletion and amortization	309,075	280,225	268,981
Settlement gain		(80,000)
Asset impairment	15,190	40,483
Total operating expenses	1,702,222	1,630,570	1,464,296
INCOME FROM OPERATIONS	259,498	372,287	331,924
Interest expense (net of interest capitalized of $1,211, $1,306 and $551, respectively)	(45,875)	(40,218)	(39,385)
Interest income	379	159	94
Equity method investment income	2,203	22,189	13,860
Equity securities income	12,906	15,696	6,398
Acquisition gain	177,043
Debt extinguishment loss			(8,148)
Other income (expense)	561	(2,621)	(332)
INCOME BEFORE INCOME TAXES	406,715	367,492	304,411
INCOME TAX EXPENSE (BENEFIT)	(211)	22	210
NET INCOME	406,926	367,470	304,201
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTEREST	(7,512)	(866)	(563)
NET INCOME ATTRIBUTABLE TO ARLP	399,414	366,604	303,638
NET INCOME ATTRIBUTABLE TO ARLP
GENERAL PARTNER		1,560	21,904
LIMITED PARTNERS	$ 399,414	$ 365,044	$ 281,734
EARNINGS PER LIMITED PARTNER UNIT - BASIC AND DILUTED	$ 3.07	$ 2.74	$ 2.80
WEIGHTED-AVERAGE NUMBER OF UNITS OUTSTANDING - BASIC AND DILUTED	128,116,670	130,758,169	98,707,696
Coal sales
SALES AND OPERATING REVENUES:
Revenues	$ 1,762,442	$ 1,844,808	$ 1,711,114
Oil & gas royalties
SALES AND OPERATING REVENUES:
Revenues	51,735
Transportation revenues
SALES AND OPERATING REVENUES:
Revenues	99,503	112,385	41,700
EXPENSES:
Transportation expenses	99,503	112,385	41,700
Other revenues
SALES AND OPERATING REVENUES:
Revenues	$ 48,040	$ 45,664	$ 43,406

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF INCOME
Interest expense, interest capitalized	$ 1,211	$ 1,306	$ 551

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
NET INCOME	$ 406,926	$ 367,470	$ 304,201
OTHER COMPREHENSIVE INCOME (LOSS)
Total adjustments	(31,122)	5,069	(13,400)
OTHER COMPREHENSIVE INCOME (LOSS)	(31,122)	5,069	(13,400)
COMPREHENSIVE INCOME	375,804	372,539	290,801
Less: Comprehensive income attributable to noncontrolling interest	(7,512)	(866)	(563)
COMPREHENSIVE INCOME ATTRIBUTABLE TO ARLP	368,292	371,673	290,238
Defined benefit pension plan
OTHER COMPREHENSIVE INCOME (LOSS)
Amortization of prior service cost	186	186	186
Net actuarial loss	(7,350)	(3,326)	(6,610)
Amortization of net actuarial loss (gain)	3,922	3,608	3,054
Total adjustments	(3,242)	468	(3,370)
Pneumoconiosis benefits
OTHER COMPREHENSIVE INCOME (LOSS)
Net actuarial loss	(23,298)	4,599	(7,938)
Amortization of net actuarial loss (gain)	(4,582)	2	(2,092)
Total adjustments	$ (27,880)	$ 4,601	$ (10,030)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 406,926	$ 367,470	$ 304,201
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	309,075	280,225	268,981
Non-cash compensation expense	11,934	12,114	12,326
Asset retirement obligations	4,087	3,926	3,793
Coal inventory adjustment to market	4,895	1,455	449
Equity investment income	(2,203)	(22,189)	(13,860)
Distributions from equity method investments	2,203	21,971	13,939
Income from equity securities paid-in-kind	(712)	(15,696)	(6,398)
Net loss (gain) on sale of property, plant and equipment	109	(1,285)	(696)
Asset impairment	15,190	40,483
Acquisition gain, net	(177,043)
Cash received on redemption of equity securities in excess of investment	(11,482)
Valuation allowance of deferred tax assets	(413)	(1,560)	(3,339)
Debt extinguishment loss			8,148
Other	5,677	3,171	6,212
Changes in operating assets and liabilities:
Trade receivables	20,841	6,757	(29,639)
Other receivables	3,726	(249)	133
Inventories, net	(35,082)	(747)	(1,449)
Prepaid expenses and other assets	6,136	7,387	(6,067)
Advance royalties	(9,876)	(8,782)	(13,591)
Accounts payable	(17,671)	(813)	25,499
Accrued taxes other than income taxes	(994)	(3,614)	2,063
Accrued payroll and related benefits	(6,538)	7,362	(5,825)
Pneumoconiosis benefits	(2,292)	1,837	(159)
Workers' compensation	3,845	(4,900)	(4,371)
Other	(15,443)	22	(4,234)
Total net adjustments	107,969	326,875	251,915
Net cash provided by operating activities	514,895	694,345	556,116
Property, plant and equipment:
Capital expenditures	(305,858)	(233,480)	(145,088)
Change in accounts payable and accrued liabilities	(81)	(1,051)	7,404
Proceeds from sale of property, plant and equipment	1,266	2,409	2,139
Contributions to equity method investments		(15,600)	(20,688)
Purchase of equity security			(100,000)
Distributions received from investments in excess of cumulative earnings	2,501	2,473	11,462
Payments for acquisitions of businesses, net of cash acquired	(320,232)
Cash received from redemption of equity securities	134,288
Net cash used in investing activities	(488,116)	(245,249)	(244,771)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings under securitization facility	184,500	304,600	100,000
Payments under securitization facility	(202,700)	(285,000)	(127,600)
Proceeds from equipment financings	63,086
Payments on equipment financings	(2,607)
Payment on term loan			(50,000)
Borrowings under revolving credit facilities	400,000	245,000	215,486
Payments under revolving credit facilities	(320,000)	(100,000)	(440,486)
Borrowing under long-term debt			400,000
Payment on long-term debt			(145,000)
Payments on finance lease obligations	(46,725)	(29,353)	(27,071)
Payment of debt issuance costs			(16,487)
Payment for debt extinguishment			(8,148)
Payments for purchases of units under unit repurchase program	(22,892)	(70,604)
Contributions to consolidated company from affiliate noncontrolling interest			251
Net settlement of withholding taxes on issuance of units in deferred compensation plans	(7,817)	(2,081)	(2,988)
Cash contributions by General Partner		41	1,105
Cash contribution by affiliated entity		2,142
Cash obtained in Simplification Transactions		1,139
Distributions paid to Partners	(278,425)	(275,902)	(240,812)
Other	(867)	(1,684)	(2,621)
Net cash used in financing activities	(234,447)	(211,702)	(344,371)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(207,668)	237,394	(33,026)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	244,150	6,756	39,782
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 36,482	$ 244,150	$ 6,756

CONSOLIDATED STATEMENT OF PARTN

CONSOLIDATED STATEMENT OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Limited Partners' Capital	General Partner's Capital (Deficit)	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest	Total
Balance at beginning of period at Dec. 31, 2016	$ 1,400,202	$ (273,788)	$ (38,540)	$ 5,550	$ 1,093,424
Balance at beginning of period (in units) at Dec. 31, 2016	74,375,025
Comprehensive income:
Net income	$ 281,734	21,904		563	304,201
Actuarially determined long-term liability adjustments			(13,400)		(13,400)
COMPREHENSIVE INCOME					290,801
Settlement of deferred compensation plans	$ (2,988)				(2,988)
Settlement of deferred compensation plans (in units)	222,011
Issuance of units to MGP in Exchange Transaction	$ 14,171	(14,171)
Issuance of units to MGP in Exchange Transaction (in units)	56,100,000
Issuance of units to SGP in Exchange Transaction	$ (320,838)	320,838
Issuance of units to SGP in Exchange Transaction (in units)	7,181
Exchange Transaction fees	$ (1,605)				(1,605)
Contributions to consolidated company from affiliate noncontrolling interest				251	251
Common unit-based compensation	12,326				12,326
Distributions on deferred common unit-based compensation	(3,248)				(3,248)
General Partners contributions		1,105			1,105
Distributions from consolidated company to affiliate noncontrolling interest				(1,016)	(1,016)
Distributions to Partners	(196,535)	(41,029)			(237,564)
Balance at end of period at Dec. 31, 2017	$ 1,183,219	14,859	(51,940)	5,348	1,151,486
Balance at end of period (in units) at Dec. 31, 2017	130,704,217
Comprehensive income:
Net income	$ 365,044	1,560		866	367,470
Actuarially determined long-term liability adjustments			5,069		5,069
COMPREHENSIVE INCOME					372,539
Settlement of deferred compensation plans	$ (2,745)				(2,745)
Settlement of deferred compensation plans (in units)	199,039
Issuance of units to SGP in Exchange Transaction (in units)	20,960
Issuance of units to Owners of SGP in Simplification Transactions	$ 14,742	(15,106)			(364)
Issuance of units to Owners of SGP in Simplification Transactions (in units)	1,322,388
Simplification Transactions fees	$ (96)				(96)
Contribution of units and cash by affiliated entity	$ 2,142				2,142
Contribution of units by affiliated entity (in units)	(467,018)
Purchase of units under unit repurchase program	$ (70,604)				(70,604)
Purchase of units under unit repurchase program (in units)	(3,684,075)
Common unit-based compensation	$ 12,114				12,114
Distributions on deferred common unit-based compensation	(3,855)				(3,855)
General Partners contributions		41			41
Distributions from consolidated company to affiliate noncontrolling interest				(924)	(924)
Distributions to Partners	(270,693)	$ (1,354)			(272,047)
Balance at end of period at Dec. 31, 2018	$ 1,229,268		(46,871)	5,290	$ 1,187,687
Balance at end of period (in units) at Dec. 31, 2018	128,095,511				128,095,511
Comprehensive income:
Net income	$ 399,414			7,512	$ 406,926
Actuarially determined long-term liability adjustments			(31,122)		(31,122)
COMPREHENSIVE INCOME					375,804
Settlement of deferred compensation plans	$ (7,817)				(7,817)
Settlement of deferred compensation plans (in units)	596,650
Purchase of units under unit repurchase program	$ (22,892)				(22,892)
Purchase of units under unit repurchase program (in units)	(1,776,564)
Common unit-based compensation	$ 11,934				11,934
Distributions on deferred common unit-based compensation	(3,670)				(3,670)
Distributions from consolidated company to affiliate noncontrolling interest				(867)	(867)
Distributions to Partners	(274,755)				(274,755)
Balance at end of period at Dec. 31, 2019	$ 1,331,482		$ (77,993)	$ 11,935	$ 1,265,424
Balance at end of period (in units) at Dec. 31, 2019	126,915,597				126,915,597

ORGANIZATION AND PRESENTATION

ORGANIZATION AND PRESENTATION	12 Months Ended
ORGANIZATION AND PRESENTATION	Dec. 31, 2019
ORGANIZATION AND PRESENTATION
ORGANIZATION AND PRESENTATION	1. ORGANIZATION AND PRESENTATION Significant Relationships Referenced in Notes to Consolidated Financial Statements ● References to "we," "us," "our" or "ARLP Partnership" mean the business and operations of Alliance Resource Partners, L.P., the parent company, as well as its consolidated subsidiaries. ● References to "ARLP" mean Alliance Resource Partners, L.P., individually as the parent company, and not on a consolidated basis. ● References to "MGP" mean Alliance Resource Management GP, LLC, ARLP's sole general partner and, prior to the Exchange Transaction discussed below, it was also referred to as the managing general partner to distinguish MGP from SGP. As a result of the Exchange Transaction, SGP no longer holds any general partner interests. ● References to "SGP" mean Alliance Resource GP, LLC, ARLP's special general partner prior to the Exchange Transaction discussed below. SGP is indirectly wholly owned by Joseph W. Craft III, the Chairman, President and Chief Executive Officer ("CEO") of MGP, and Kathleen S. Craft, who are collectively referred to in such capacity as the "Owners of SGP." The Owners of SGP held approximately 34.48% of the outstanding AHGP common units prior to the Simplification Transactions discussed below. ● References to "Intermediate Partnership" mean Alliance Resource Operating Partners, L.P., the intermediate partnership of Alliance Resource Partners, L.P. ● References to "Alliance Coal" mean Alliance Coal, LLC, the holding company for the coal mining operations of Alliance Resource Operating Partners, L.P. ● References to "AHGP" mean Alliance Holdings GP, L.P., individually and not on a consolidated basis as the parent company of MGP prior to the Simplification Transactions discussed below and as a wholly owned subsidiary of ARLP subsequent to the Simplification Transactions. Organization ARLP is a Delaware limited partnership listed on the NASDAQ Global Select Market under the ticker symbol "ARLP." ARLP was formed in May 1999 and completed its initial public offering on August 19, 1999 when it acquired substantially all of the coal production and marketing assets of Alliance Resource Holdings, Inc., a Delaware corporation ("ARH"), and its subsidiaries. We are managed by our sole general partner, MGP, a Delaware limited liability company which holds a non-economic general partner interest in ARLP. Prior to the Simplification Transactions, MGP was a wholly owned indirect subsidiary of AHGP. Alliance GP, LLC ("AGP"), which is indirectly wholly owned by Mr. Craft, was the general partner of AHGP prior to the Simplification Transactions and became the direct owner of MGP as a result of the transactions. See discussions under Partnership Simplification Partnership Simplification On July 28, 2017, the conflicts committee ("Conflicts Committee") of the board of directors ("Board of Directors") of MGP and AGP's board of directors approved a transaction to simplify our partnership structure. Pursuant to that transaction, which closed on the same date, MGP contributed to ARLP all of its incentive distribution rights ("IDRs") and its 0.99% managing general partner interest in ARLP in exchange for 56,100,000 ARLP common units and a non-economic general partner interest in ARLP. In conjunction with this transaction and on the same economic basis as MGP, SGP also contributed to ARLP its 0.01% general partner interests in both ARLP and the Intermediate Partnership in exchange for 28,141 ARLP common units (collectively the "Exchange Transaction"). On February 22, 2018, the Board of Directors and the board of directors of AGP approved a simplification agreement (the "Simplification Agreement"), pursuant to which, among other things, through a series of transactions (the "Simplification Transactions"): i. AHGP would become a wholly owned subsidiary of ARLP, ii. all of the issued and outstanding AHGP common units would be canceled and converted into the right to receive the ARLP common units held by AHGP and its subsidiaries, iii. in exchange for a number of ARLP common units calculated pursuant to the Simplification Agreement, MGP's 1.0001% general partner interest in our Intermediate Partnership and MGP's 0.001% managing member interest in our subsidiary, Alliance Coal, would be contributed to us, and iv. MGP would remain ARLP's sole general partner and would be a wholly owned subsidiary of AGP, and thus no control, management, or governance changes with respect to our business would occur. The Simplification Agreement and the transactions contemplated thereby were approved by the written consent of approximately 68% of the holders of AHGP common units outstanding as of April 25, 2018, the record date for the consent solicitation. On May 31, 2018, ARLP, AHGP and the other parties to the Simplification Agreement completed the transactions contemplated by the Simplification Agreement. As part of the Simplification Transactions, (i) each AHGP common unit that was issued and outstanding at the effective time of the Simplification Transactions was canceled and converted into the right to receive a portion of the ARLP common units held by AHGP and its subsidiaries, and (ii) SGP became the sole limited partner in AHGP. Each outstanding AHGP common unit, other than certain AHGP common units held by the Owners of SGP, converted into the right to receive approximately 1.4782 ARLP common units held by AHGP and its subsidiaries. The remaining AHGP common units held by the Owners of SGP were canceled and converted into the right to receive 29,188,997 ARLP common units which equaled (i) the product of the number of certain AHGP common units held by the Owners of SGP multiplied by 1.4782, minus (ii) 1,322,388 ARLP common units. In addition, ARLP issued 1,322,388 ARLP common units to the Owners of SGP in exchange for causing SGP to contribute to ARLP its remaining limited partner interest in AHGP, which included AHGP's indirect ownership of a 1.0001% general partner interest in the Intermediate Partnership and a 0.001% managing member interest in Alliance Coal, resulting in an overall exchange ratio to the Owners of SGP equal to that of the other AHGP unitholders. Upon the issuance of ARLP common units to the Owners of SGP in exchange for the limited partner interest in AHGP, ARLP became a) the sole limited partner of AHGP and b) through AHGP, the indirect owner of a 1.0001% general partner interest in the Intermediate Partnership and a 0.001% managing member interest in Alliance Coal. AllDale I & II Acquisition On January 3, 2019 (the "AllDale Acquisition Date"), we acquired all of the limited partner interests not owned by Cavalier Minerals JV, LLC ("Cavalier Minerals") in AllDale Minerals LP ("AllDale I") and AllDale Minerals II, LP ("AllDale II", and collectively with AllDale I, "AllDale I & II") and the general partner interests in AllDale I & II (the "AllDale Acquisition"). As a result of the AllDale Acquisition and our previous investments held through Cavalier Minerals, we acquired control of approximately 43,000 net royalty acres in premier oil & gas resource plays. The AllDale Acquisition provides us with diversified exposure to industry leading operators and is consistent with our general business strategy to grow our Minerals segment. See Note 3 – Acquisitions for more information. Wing Acquisition On August 2, 2019, our subsidiary AR Midland, LP ("AR Midland") acquired from Wing Resources LLC and Wing Resources II LLC (collectively, "Wing") approximately 9,000 net royalty acres in the Midland Basin, with exposure to more than 400,000 gross acres (the "Wing Acquisition"). The Wing Acquisition enhances our ownership position in the Permian Basin, expands our exposure to industry leading operators and furthers our business strategy to grow our Minerals segment. Following the Wing Acquisition, we hold approximately 55,700 net royalty acres in premier oil & gas basins including our investment in AllDale Minerals III, LP ("AllDale III"). See Note 3 – Acquisitions for more information. Presentation The consolidated financial statements include the accounts and operations of the ARLP Partnership and present our financial position as of December 31, 2019 and 2018, and results of our operations, comprehensive income, cash flows and changes in partners' capital for each of the three years in the period ended December 31, 2019. All of our intercompany transactions and accounts have been eliminated. As a result of the AllDale Acquisition, we now control the underlying oil & gas mineral interests held by AllDale I & II. This control over the oil & gas mineral interests held by AllDale I & II reflects a strategic change in how we manage our business and how resources are allocated by our chief operating decision maker. Due to this strategic change, we realigned our reportable segments in 2019 to include our oil & gas mineral interests within a new Minerals reportable segment. In August 2019, we added the Wing Acquisition to the Minerals reportable segment. As part of our realignment, we have also included the operations of our Mt. Vernon Transfer Terminal, LLC ("Mt. Vernon") and Mid-America Carbonates, LLC ("MAC") subsidiaries in the Illinois Basin reportable segment rather than Other and Corporate to better reflect our Illinois Basin related activities. Prior periods have been recast to include our oil & gas mineral interests in the Minerals segment, and Mt. Vernon and MAC in the Illinois Basin segment. See Note 23 – Segment Information for further discussion of our reportable segments.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Dec. 31, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Consolidation — Variable Interest Entity ("VIE") — To determine a VIE's primary beneficiary, we perform a qualitative assessment to determine which party, if any, has the power to direct activities of the VIE and the obligation to absorb losses and/or receive its benefits. This assessment involves identifying the activities that most significantly impact the VIE's economic performance and determine whether it, or another party, has the power to direct those activities. When evaluating whether we are the primary beneficiary of a VIE, we perform a qualitative analysis that considers the design of the VIE, the nature of our involvement and the variable interests held by other parties. See Note 11 – Variable Interest Entities for further information. Estimates — ● Impairment assessments of investments, property, plant and equipment, and goodwill; ● Asset retirement obligations; ● Pension valuation variables; ● Workers' compensation and pneumoconiosis valuation variables; ● Acquisition related purchase price allocations; and ● Life of mine assumptions; ● Oil & gas reserve quantities and carrying amounts; and ● Determination of oil & gas revenue accruals These significant estimates and assumptions are discussed throughout these notes to the consolidated financial statements. Fair Value Measurements — between market participants at the measurement date. Fair value is based upon assumptions that market participants would use when pricing an asset or liability, including assumptions about risk and risks inherent in valuation techniques and inputs to valuations. Fair value measurements assume that the transaction occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability (the market for which the reporting entity would be able to maximize the amount received or minimize the amount paid). Valuation techniques used in our fair value measurements are based upon observable and unobservable inputs. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our own market assumptions. We use the following fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value into three broad levels: ● Level 1 – Quoted prices for identical assets and liabilities in active markets that we have the ability to access at the measurement date. ● Level 2 – Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model derived valuations whose inputs are observable or whose significant value drivers are observable. ● Level 3 – Unobservable inputs for the asset or liability including situations where there is little, if any, market activity for the asset or liability. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall into different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement requires judgment, considering factors specific to the asset or liability. Significant fair value measurements are used in our significant estimates and are discussed throughout these notes. Cash and Cash Equivalents — Cash Management — Inventories — Business Combinations — Goodwill — Property, Plant and Equipment — current production estimates, are depreciated or depleted using the units-of-production method over a range from 1 to 28 years. Mining equipment and other plant and equipment assets are depreciated principally using the straight-line method over the estimated useful lives of the assets, ranging from 1 to 28 years, limited by the remaining estimated life of each mine. Depreciable lives for buildings, office equipment and improvements range from 1 to 25 years. Gains or losses arising from retirements are included in operating expenses. Depletion of coal mineral rights is provided on the basis of tonnage mined in relation to estimated recoverable tonnage, which equals estimated proven and probable reserves. Therefore, our coal mineral rights are depleted based on only proven and probable reserves. See Oil & Gas Reserve Quantities and Carrying Amounts below for a discussion of our accounting policies for oil & gas properties. Mine Development Costs — Long-Lived Asset Impairment — Oil & Gas Reserve Quantities and Carrying Amounts Mineral interests in oil & gas properties are grouped using a reasonable aggregation of properties with a common geological structural feature or stratigraphic condition, which we may also refer to as a depletable group. Mineral interests in proved oil & gas properties are depleted based on the units-of-production method. Proved reserves are quantities of oil & gas that can be estimated with reasonable certainty to be recoverable in the future from a given date forward, from known reservoirs, under existing economic conditions, operating methods, and government regulations. Proved developed resources are the quantities expected to be recovered through our operators' existing wells with existing equipment, infrastructure and operating methods. We evaluate impairment of our mineral interests in proved properties whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. This evaluation is performed on a depletable group basis. We compare the undiscounted projected future cash flows expected in connection with a depletable group to its unamortized carrying amount to determine recoverability. When the carrying amount of a depletable group exceeds its estimated undiscounted future cash flows, the carrying amount is written down to its fair value, which is measured as the present value of the projected future cash flows of such properties. The factors used to determine fair value include estimates of proved reserves, future commodity prices, timing of future production, future expenditures, and a risk-adjusted discount rate. Our mineral interests in unproved properties are also assessed for impairment periodically on a depletable group basis when facts and circumstances indicate that the carrying value may not be recoverable. Impairment of individual unproved properties whose acquisition costs are relatively significant are assessed on a property-by-property basis, and an impairment loss is recognized to the extent the carrying value exceeds the estimated recoverable value for the property. Impairment of unproved properties whose acquisition costs are not individually significant are assessed on a group basis. Any amount of loss to be recognized and the amount of a valuation allowance needed to provide for impairment of those properties is determined by amortizing those properties in the aggregate on the basis of historical experience and other relevant information, such as the relative proportion of such properties on which proved reserves have been found in the past. The carrying value of unproved properties, including unleased mineral rights, are determined based on management's assessment of fair value using factors similar to those previously noted for proved properties, as well as geographic and geologic data. Upon the sale of a complete depletable group, the book value thereof, less proceeds or salvage value, are charged to income. Upon the sale or retirement of an aggregation of interests which make up less than a complete depletable group, the proceeds are credited to accumulated depreciation, depletion and amortization, unless doing so would significantly alter the depreciation, depletion and amortization rate of the depletable group, in which case a gain or loss would be recorded. Intangibles — Prepaid expenses and other assets Other long-term assets December 31, 2019 December 31, 2018 Accumulated Intangibles, Accumulated Intangibles, Original Cost Amortization Net Original Cost Amortization Net (in thousands) Non-compete agreements $ 9,803 $ (9,440) $ 363 $ 9,697 $ (8,385) $ 1,312 Customer contracts and other 32,371 (24,258) 8,113 23,000 (16,293) 6,707 Mining permits 1,500 (307) 1,193 1,500 (241) 1,259 Total $ 43,674 $ (34,005) $ 9,669 $ 34,197 $ (24,919) $ 9,278 Amortization expense attributable to intangible assets is estimated as follows: Year Ended December 31, (in thousands) 2020 $ 4,495 2021 2,952 2022 647 2023 647 2024 66 Thereafter 862 Investments Our investments and ownership interests in entities in which we do not have a controlling financial interest are accounted for under the equity method of accounting if we have the ability to exercise significant influence over the entity. Investments accounted for under the equity method are initially recorded at cost, and the difference between the basis of our investment and the underlying equity in the net assets of the joint venture at the investment date, if any, is amortized over the lives of the related assets that gave rise to the difference. As of December 31, 2019, we held an equity method investment in AllDale III through our subsidiary, Alliance Minerals, LLC ("Alliance Minerals"). Prior to the AllDale Acquisition, our equity method investments also included AllDale I & II, both held through Cavalier Minerals. AllDale III and AllDale I & II are collectively referred to as the "AllDale Partnerships." See Note 12 – Investments for further discussion of our equity method investment in AllDale III and Note 3 – Acquisitions for discussion of the AllDale Acquisition. We review our investments for impairment whenever events or changes in circumstances indicate a loss in the value of the investment may be other-than-temporary. Advance Royalties — Advance royalties December 31, 2019 2018 (in thousands) Advance royalties, affiliates (see Note 20 – Related-Party Transactions) $ 41,216 $ 32,645 Advance royalties, third-parties 12,685 11,552 Total advance royalties $ 53,901 $ 44,197 Asset Retirement Obligations — Pension Benefits — The discount rate is determined for our pension benefit plan based on an approach specific to our plan. The year end discount rate is determined considering a yield curve comprised of high-quality corporate bonds and the timing of the expected benefit cash flows. The expected long-term rate of return on plan assets is determined based on broad equity and bond indices, the investment goals and objectives, the target investment allocation and on the average annual total return for each asset class. Unrecognized actuarial gains and losses and unrecognized prior service costs and credits are deferred and recorded in accumulated other comprehensive loss until amortized as a component of net periodic benefit cost. Unrecognized actuarial gains and losses in excess of 10% of the greater of the benefit obligation or the market-related value of plan assets are amortized over the participants' average remaining future years of service. Workers ' Compensation and Pneumoconiosis (Black Lung) Benefits — We provide income replacement and medical treatment for work-related traumatic injury claims as required by applicable state laws. Workers' compensation laws also compensate survivors of workers who suffer employment related deaths. Our liability for traumatic injury claims is the estimated present value of current workers' compensation benefits, based on our actuarial estimates. Our actuarial calculations are based on a blend of actuarial projection methods and numerous assumptions including claim development patterns, mortality, medical costs and interest rates. Our pneumoconiosis benefits liability is calculated using the service cost method based on the actuarial present value of the estimated pneumoconiosis obligation. Our actuarial calculations are based on numerous assumptions including claim development patterns, medical costs and mortality. Actuarial gains or losses are amortized over the remaining service period of active miners. See Note 19 – Accrued Workers' Compensation and Pneumoconiosis Benefits for more information on Workers' Compensation and Pneumoconiosis Benefits. Coal Revenue Recognition — The estimated transaction price from each of our contracts is based on the total amount of consideration we expect to be entitled to under the contract. Included in the transaction price for certain coal supply contracts is the impact of variable consideration, including quality price adjustments, handling services, government imposition claims, per ton price fluctuations based on certain coal sales price indices and anticipated payments in lieu of shipments. We have constrained the expected value of variable consideration in our estimation of transaction price and only included this consideration to the extent that it is probable that a significant revenue reversal will not occur. The estimated transaction price for each contract is allocated to our performance obligations based on relative standalone selling prices determined at contract inception. Variable consideration is allocated to a specific part of the contract in many instances, such as if the variable consideration is based on production activities for coal delivered during a certain period or the outcome of a customer's ability to accept coal shipments over a certain period. Contract assets are recorded as trade receivables and reported separately in our consolidated balance sheet from other contract assets as title passes to the customer and our right to consideration becomes unconditional. Payments for coal shipments are typically due within two four weeks Oil & Gas Revenue Recognition — We also periodically earn revenue from lease bonuses. We generate lease bonus revenue by leasing our mineral interests to exploration and production companies. A lease agreement represents our contract with an operator, which is generally an exploration and production company. The contract will a) generally transfer the rights to any oil or gas discovered, b) grant us a right to a specified royalty interest from the operator, and c) require the operator to commence drilling and complete operations within a specified time period. Control of the minerals transfers to the operator when the lease agreement is executed. At the time we execute the lease agreement, we expect to receive the lease bonus payment within a reasonable time, though in no case more than one year, such that we do not adjust the expected amount of consideration for the effects of any significant financing component. As a non-operator, we have limited visibility into the timing of when new wells start producing, in addition, production statements may not be received for 30 to 90 days or more after the date production is delivered. As a result, we are required to estimate the amount of production delivered to the purchaser and the price that will be received for the sale of the product. The expected sales volumes and prices from our properties are estimated and recorded within the Trade receivables Common Unit-Based Compensation — We utilize the Supplemental Executive Retirement Plan ("SERP") to provide deferred compensation benefits for certain officers and key employees. All allocations made to participants under the SERP are made in the form of "phantom" ARLP units and SERP distributions will be settled in the form of ARLP common units. The SERP is administered by the Compensation Committee. Our directors participate in the MGP Amended and Restated Deferred Compensation Plan for Directors ("Directors' Deferred Compensation Plan"). Pursuant to the Directors' Deferred Compensation Plan, for amounts deferred either automatically or at the election of the director, a notional account is established and credited with notional common units of ARLP, described in the Directors' Deferred Compensation Plan as "phantom" units. Distributions from the Directors' Deferred Compensation Plan will be settled in the form of ARLP common units. For both the SERP and Directors' Deferred Compensation Plan, when quarterly cash distributions are made with respect to ARLP common units, an amount equal to such quarterly distribution is credited to each participant's notional account as additional phantom units. All grants of phantom units under the SERP and Directors' Deferred Compensation Plan vest immediately. The fair value of restricted common unit grants under the LTIP, SERP and the Directors' Deferred Compensation Plan are determined on the grant date of the award and recognized as compensation expense on a pro rata basis for LTIP and SERP awards, as appropriate, over the requisite service period. Compensation expense is fully recognized on the grant date for quarterly distributions credited to SERP accounts and Directors' Deferred Compensation Plan awards. The corresponding liability is classified as equity and included in limited partners' capital in the consolidated financial statements (See Note 16 – Compensation Plans). Income Taxes and the taxable income allocation requirements under our partnership agreement. Individual unitholders have different investment bases depending upon the timing and price of acquisition of their partnership units. Furthermore, each unitholder's tax accounting, which is partially dependent upon the unitholder's tax position, differs from the accounting followed in our consolidated financial statements. Accordingly, the aggregate difference in the basis of our net assets for financial and tax reporting purposes cannot be readily determined because information regarding each unitholder's tax attributes in our partnership is not available to us. We have certain subsidiaries that are subject to federal and state income taxes. These income taxes are not material to our financial position or results of operations. New Accounting Standards Issued and Adopted — January 1, 2019 As part of our transition there are a number of practical expedients available in the new standard. We elected a package of practical expedients that, among other things, allows us to not reassess the lease classification of expired or existing leases. In addition to the package of practical expedients, we also elected to use a practical expedient allowing us to use hindsight in determining the lease term for existing leases. New Accounting Standards Issued and Not Yet Adopted — Financial Instruments–Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

ACQUISITIONS

ACQUISITIONS	12 Months Ended
ACQUISITIONS	Dec. 31, 2019
ACQUISITIONS
ACQUISITIONS	3. ACQUISITION S AllDale I & II On the AllDale Acquisition Date, we acquired all of the limited partner interests not owned by Cavalier Minerals in AllDale I & II and the general partner interests in AllDale I & II for $176.2 million, which was funded with cash on hand and borrowings under the Revolving Credit Facility. As a result of the AllDale Acquisition and our previous investments held through Cavalier Minerals, we acquired control of approximately 43,000 net royalty acres strategically positioned primarily in the core of the Permian (Delaware and Midland), Anadarko (SCOOP/STACK) and Williston (Bakken) Basins. The AllDale Acquisition provides us with diversified exposure to industry leading operators and is consistent with our general business strategy to grow our Minerals segment. Because the underlying mineral interests held by AllDale I & II include royalty interests in both producing properties and unproved properties, we have determined that the AllDale Acquisition should be accounted for as a business combination and the underlying assets and liabilities of AllDale I & II should be recorded at their AllDale Acquisition Date fair value on our consolidated balance sheet. The final total fair value of the cash paid in the AllDale Acquisition and our previous investments were as follows: As of January 3, 2019 (in thousands) Cash $ 176,205 Previously held investments 307,322 Total $ 483,527 Prior to the AllDale Acquisition Date, we accounted for our investments in AllDale I & II, held through Cavalier Minerals, as equity method investments. The combined fair value of our equity method investments on the AllDale Acquisition Date was $307.3 million. We re-measured our equity method investments, which had an aggregate carrying value of $130.3 million immediately prior to the AllDale Acquisition. The re-measurement resulted in a gain of $177.0 million which is recorded in the Acquisition gain line item in our consolidated statements of income. During the third quarter of 2019, we finalized our purchase price accounting, which resulted in adjustments to our mineral interests in proved and unproved properties due to additional information received from operators of the mineral interests about reserve and production quantities and projections that represented facts and circumstances that existed as of the AllDale Acquisition Date. In addition, we reduced our receivables by $1.3 million as a result of information received from operators concerning royalty payments owed to us from production that occurred prior to the AllDale Acquisition Date. The following table summarizes the preliminary and final fair value allocation of assets acquired and liabilities assumed as of the AllDale Acquisition Date: Preliminary Adjustments Final (in thousands) Cash and cash equivalents $ 900 $ 900 Mineral interests in proved properties 159,617 24,415 184,032 Mineral interests in unproved properties 314,084 (22,894) 291,190 Receivables 10,602 (1,276) 9,326 Accounts payable (1,921) (1,921) Net assets acquired $ 483,282 $ 483,527 Our previous equity method investments in AllDale I & II were held through Cavalier Minerals. Bluegrass Minerals Management, LLC ("Bluegrass Minerals") continues to hold a 4% membership interest (the "Bluegrass Interest") as well as a profits interest in Cavalier Minerals as it did before the AllDale Acquisition. This Bluegrass Interest represents an indirect noncontrolling interest in AllDale I & II. The AllDale Acquisition Date fair value of the Bluegrass Interest was $12.3 million. The fair value of our previous equity method investments, the mineral interests and the Bluegrass Interest were determined using an income approach primarily comprised of discounted cash flow models. The assumptions used in the discounted cash flow models include estimated production, projected cash flows, forward oil & gas prices and a risk adjusted discount rate. Certain assumptions used are not observable in active markets, therefore the fair value measurements represent Level 3 fair value measurements. AllDale I & II's carrying value of the receivables and accounts payable represent their fair value given their short-term nature. The amounts of revenue and earnings, exclusive of the acquisition gain, of AllDale I & II included in our consolidated statements of income since the AllDale Acquisition Date are as follows: Year Ended December 31, 2019 (in thousands) Revenue $ 48,411 Net income 18,543 The following represents our actual and pro forma consolidated revenues and net income for the year ended December 31, 2018. Pro forma revenues and net income assumes AllDale I & II had been included in our consolidated results since January 1, 2018. These amounts have been calculated after applying our accounting policies. Pro forma information is not necessary for the year ended December 31, 2019 as the AllDale Acquisition occurred at the beginning of the year. Additionally, our results have been adjusted to remove the effect of our past equity method investments in AllDale I & II. Year Ended December 31, 2018 (in thousands) Total revenues As reported $ 2,002,857 Pro forma 2,042,545 Net income As reported $ 367,470 Pro forma 358,741 Wing On August 2, 2019 (the "Wing Acquisition Date"), our subsidiary, AR Midland acquired from Wing approximately 9,000 net royalty acres in the Midland Basin, with exposure to more than 400,000 gross acres, for a cash purchase price of $144.9 million. The purchase price was funded with cash on hand and borrowings under our Revolving Credit Facility discussed in Note 7 – Long-Term Debt. The Wing Acquisition enhances our ownership position in the Permian Basin, expands our exposure to industry leading operators and furthers our business strategy to grow our Minerals segment. Concurrent with the Wing Acquisition, JC Resources LP, an entity owned by Joseph W. Craft III, the Chairman, President and CEO of MGP ("Mr. Craft"), acquired from Wing, in a separate transaction, mineral interests that we elected not to acquire. Because the mineral interests acquired in the Wing Acquisition include royalty interests in both producing properties and unproved properties, we have determined that the acquisition should be accounted for as a business combination and the underlying assets should be recorded at fair value as of the Wing Acquisition Date on our consolidated balance sheet. We consider our fair value measurements to be preliminary as we continue to obtain additional information from operators regarding reserve and production quantities and projections for the mineral interests we acquired. During the fourth quarter of 2019, we recorded adjustments to our mineral interests in proved and unproved properties due to additional information received from operators that represented facts and circumstances that existed as of the Wing Acquisition Date. The following table summarizes the preliminary fair value allocation of assets acquired as of the Wing Acquisition Date incorporating measurement period adjustments made to the allocation: As Previously Reported Adjustments Adjusted (in thousands) Mineral interests in proved properties $ 55,619 2,465 $ 58,084 Mineral interests in unproved properties 87,441 (2,465) 84,976 Receivables 1,867 1,867 Net assets acquired $ 144,927 $ 144,927 The fair value of the mineral interests was determined using a weighting of both income and market approaches. Our income approach primarily comprised of a discounted cash flow model. The assumptions used in the discounted cash flow model included estimated production, projected cash flows, forward oil & gas prices and a risk-adjusted discount rate. Our market approach consisted of the observation of recent acquisitions in the Permian Basin to determine a market price for similar mineral interests. Certain assumptions used in our valuation are not observable in active markets; therefore, the fair value measurements represent Level 3 fair value measurements. The carrying value of the receivables represent their fair value given their short-term nature. The amounts of revenue and earnings from the mineral interests acquired in the Wing Acquisition included in our consolidated statements of income since the Wing Acquisition Date are as follows: Year Ended December 31, 2019 (in thousands) Revenue $ 4,625 Net income 1,291 The following represents our actual and pro forma consolidated revenues and net income for the years ended December 31, 2019 and 2018. Pro forma revenues and net income assumes the mineral interests acquired in the Wing Acquisition had been included in our consolidated results since January 1, 2018. These pro forma amounts have been calculated after applying our accounting policies. Year Ended December 31, 2019 2018 (in thousands) Total revenues As reported $ 1,961,720 $ 2,002,857 Pro forma 1,966,291 2,008,559 Net income As reported $ 406,926 $ 367,470 Pro forma 411,217 372,810

LONG-LIVED ASSET IMPAIRMENTS

LONG-LIVED ASSET IMPAIRMENTS	12 Months Ended
LONG-LIVED ASSET IMPAIRMENTS	Dec. 31, 2019
LONG-LIVED ASSET IMPAIRMENTS
LONG-LIVED ASSET IMPAIRMENTS	4. LONG-LIVED ASSET IMPAIRMENT S We ceased coal production effective August 16, 2019 at our Dotiki mine to focus on shifting production to our other lower-cost mines in our Illinois Basin segment. Accordingly, we adjusted the carrying value of Dotiki's assets from $35.9 million to its fair value of $25.8 million and accrued scheduled payments of $5.1 million to WKY CoalPlay for leased reserves from which we may not receive future economic benefit. The resulting impairment charge totaled $15.2 million. See Note 11 – Variable Interest Entities for more information about WKY CoalPlay. Previously, in the fourth quarter of 2018, we reduced Dotiki’s economic mine life which resulted in a $34.3 million impairment charge, and the related adjustment of Dotiki’s asset carrying value from $85.3 million to its fair value of $51.0 million. Also in the fourth quarter of 2018, a decrease in the fair value of an option entitling us to lease certain coal reserves within the Illinois Basin Segment resulted in an impairment charge of $6.2 million. The fair value of the impaired assets was determined using a combination of market and income approaches, both of which represent Level 3 fair value measurements under the fair value hierarchy. The fair value analysis used assumptions of marketability of certain assets as well as discounted cash flows over the remaining life of the assets. See Note 2 – Summary of Significant Accounting Policies – Long-Lived Asset Impairment for more information on our accounting policy for asset impairments.

INVENTORIES

INVENTORIES	12 Months Ended
INVENTORIES	Dec. 31, 2019
INVENTORIES
INVENTORIES	5. INVENTORIES Inventories consist of the following : December 31, 2019 2018 (in thousands) Coal $ 63,645 $ 20,929 Supplies (net of reserve for obsolescence of $5,555 and $5,453, respectively) 37,660 38,277 Total inventories, net $ 101,305 $ 59,206 See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for inventories.

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	12 Months Ended
PROPERTY, PLANT AND EQUIPMENT	Dec. 31, 2019
PROPERTY, PLANT AND EQUIPMENT
PROPERTY, PLANT AND EQUIPMENT	6. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consist of the following: December 31, 2019 2018 (in thousands) Mining equipment and processing facilities $ 1,937,642 $ 1,851,479 Land and coal mineral rights 453,237 445,411 Oil & gas mineral interests (1) 618,282 — Buildings, office equipment and improvements 304,111 287,053 Construction and mine development in progress 86,876 71,190 Mine development costs 283,860 270,675 Property, plant and equipment, at cost 3,684,008 2,925,808 Less accumulated depreciation, depletion and amortization (1,675,022) (1,513,450) Total property, plant and equipment, net $ 2,008,986 $ 1,412,358 (1) Oil & gas mineral interests acquired in the AllDale and Wing Acquisitions. See Note 3 – Acquisitions for more information. At December 31, 2019 and 2018, land and coal mineral rights above include $40.1 million and $49.2 million, respectively, of carrying value associated with coal reserves attributable to properties where we or a third party to which we lease reserves are not currently engaged in mining operations or leasing to third parties, and therefore, the coal reserves are not currently being depleted. We believe that the carrying value of these coal reserves will be recovered. At December 31, 2019, our oil & gas mineral interests noted in the table above includes the carrying value of our unproved oil & gas mineral interests totaling $376.2 million. As discussed in Note 2 – Summary of Significant Accounting Policies, we generally do not record depletion expense for our unproved oil & gas mineral interests; however, we do review for impairment as needed throughout the year. During 2019, we incurred $13.2 million in mine development costs, primarily related to the development of our Excel #5 mine at our MC Mining complex. During 2018, we reduced mine development costs by $9.9 million primarily related to the impairment of our Dotiki mine. Regarding the mine development costs for MC Mining's Excel #5 mine, we had no incidental production during this development phase and thus no related capitalized development costs associated with incidental production. All past capitalized mine development costs are associated with other mines that shifted to the production phase in past years and we are amortizing these costs accordingly. We believe that the carrying value of the past development costs will be recovered. For information regarding long-lived asset impairments please see Note 4 – Long-Lived Asset Impairments. See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for property, plant and equipment.

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
LONG-TERM DEBT	Dec. 31, 2019
LONG-TERM DEBT
LONG-TERM DEBT	7. LONG-TERM DEBT Long-term debt consists of the following: Unamortized Discount and Principal Debt Issuance Costs December 31, December 31, 2019 2018 2019 2018 (in thousands) Revolving credit facility $ 255,000 $ 175,000 $ (3,050) $ (5,203) Senior notes 400,000 400,000 (4,879) (5,793) Securitization facility 73,800 92,000 — — May 2019 equipment financing 8,199 — — — November 2019 equipment financing 52,281 — — — 789,280 667,000 (7,929) (10,996) Less current maturities (13,157) (92,000) — — Total long-term debt $ 776,123 $ 575,000 $ (7,929) $ (10,996) Credit Facility. The Credit Agreement is guaranteed by all of the material direct and indirect subsidiaries of our Intermediate Partnership, and is secured by substantially all of the Intermediate Partnership's assets. Borrowings under the Revolving Credit Facility bear interest, at the option of the Intermediate Partnership, at either (i) the Base Rate at the greater of three benchmarks or (ii) a Eurodollar Rate, plus margins for (i) or (ii), as applicable, that fluctuate depending upon the ratio of Consolidated Debt to Consolidated Cash Flow (each as defined in the Credit Agreement). The Eurodollar Rate, with applicable margin, under the Revolving Credit Facility was 4.32% as of December 31, 2019. At December 31, 2019, we had $9.3 million of letters of credit outstanding with $230.5 million available for borrowing under the Revolving Credit Facility. We currently incur an annual commitment fee of 0.35% on the undrawn portion of the Revolving Credit Facility. We utilize the Revolving Credit Facility, as appropriate, for working capital requirements, capital expenditures and investments, scheduled debt payments and distribution payments. The Credit Agreement contains various restrictions affecting our Intermediate Partnership and its subsidiaries including, among other things, restrictions on incurrence of additional indebtedness and liens, sale of assets, investments, mergers and consolidations and transactions with affiliates, in each case subject to various exceptions, and the payment of cash distributions by our Intermediate Partnership if such payment would result in a certain fixed charge coverage ratio (as defined in the Credit Agreement). The Credit Agreement requires the Intermediate Partnership to maintain (a) a debt to cash flow ratio of not more than 2.5 to 1.0 and (b) a cash flow to interest expense ratio of not less than 3.0 to 1.0, in each case, during the four Senior Notes. principal amount of the Senior Notes with the net cash proceeds of one or more equity offerings at a redemption price equal to 107.5% of the principal amount redeemed, plus accrued and unpaid interest, if any, to the redemption date. The issuers of the Senior Notes may also redeem all or a part of the notes at any time on or after May 1, 2020, at redemption prices set forth in the indenture governing the Senior Notes. At any time prior to May 1, 2020, the issuers of the Senior Notes may redeem the Senior Notes at a redemption price equal to the principal amount of the Senior Notes plus a "make-whole" premium, plus accrued and unpaid interest, if any, to the redemption date. The net proceeds from issuance of the Senior Notes and cash on hand were used to repay previous debt obligations (including a make-whole payment of $8.1 million). We incurred discount and debt issuance costs of $7.3 million in connection with issuance of the Senior Notes. These costs are deferred and are currently being amortized as a component of interest expense over the Term. Accounts Receivable Securitization May 2019 Equipment Financing. November 2019 Equipment Financing. Other. Aggregate maturities of long-term debt are payable as follows: Year Ended December 31, (in thousands) 2020 $ 13,157 2021 342,648 2022 12,403 2023 21,072 2024 — Thereafter 400,000 $ 789,280

LEASES

LEASES	12 Months Ended
LEASES	Dec. 31, 2019
LEASES
LEASES	8. LEASES The components of lease expense were as follows: December 31, 2019 (in thousands) Finance lease cost: Amortization of right-of-use assets $ 14,608 Interest on lease liabilities 2,085 Operating lease cost 9,169 Short-term lease cost 464 Variable lease cost 1,360 Total lease cost $ 27,686 Rental expense was $11.0 million, $14.9 million and $16.0 million for the years ended December 31, 2019, 2018 and 2017, respectively. Supplemental cash flow information related to leases was as follows: December 31, 2019 (in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 9,124 Operating cash flows for finance leases $ 891 Financing cash flows for finance leases $ 46,725 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ 25,593 Supplemental balance sheet information related to leases was as follows: December 31, 2019 2018 (in thousands) Finance leases: Property and equipment finance lease assets, gross $ 30,610 $ 141,019 Accumulated depreciation (20,564) (74,576) Property and equipment finance lease assets, net $ 10,046 $ 66,443 December 31, 2019 Weighted average remaining lease term Operating leases 13.1 years Finance leases 1.6 years Weighted average discount rate Operating leases 6.0 % Finance leases 6.0 % Maturities of lease liabilities as of December 31, 2019 were as follows: Operating leases Finance leases (in thousands) 2020 $ 3,832 $ 8,747 2021 2,280 912 2022 2,217 912 2023 2,040 139 2024 1,820 139 Thereafter 13,539 419 Total lease payments 25,728 11,268 Less imputed interest (8,161) (676) Total $ 17,567 $ 10,592

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
FAIR VALUE MEASUREMENTS	Dec. 31, 2019
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS	9. FAIR VALUE MEASUREMENTS The following table summarizes our fair value measurements within the hierarchy not included elsewhere in these notes: December 31, 2019 December 31, 2018 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 (in thousands) Long-term debt $ — $ 736,206 $ — $ — $ 669,864 $ — Total $ — $ 736,206 $ — $ — $ 669,864 $ — See Note 2 – Summary of Significant Accounting Policies – Fair Value Measurements for more information regarding fair value hierarchy levels. The carrying amounts for cash equivalents, accounts receivable, accounts payable, accrued and other liabilities, due from affiliates and due to affiliates approximate fair value due to the short maturity of those instruments. The estimated fair value of our long-term debt, including current maturities, is based on interest rates that we believe are currently available to us in active markets for issuance of debt with similar terms and remaining maturities (See Note 7 – Long-Term Debt). The fair value of debt, which is based upon these interest rates, is classified as a Level 2 measurement under the fair value hierarchy.

PARTNERS' CAPITAL

PARTNERS' CAPITAL	12 Months Ended
PARTNERS' CAPITAL	Dec. 31, 2019
PARTNERS' CAPITAL
PARTNERS' CAPITAL	10. PARTNERS' CAPITAL Distributions We distribute 100% of our available cash that is not used for unit repurchases within 45 days after the end of each quarter to unitholders of record. Available cash is generally defined in the partnership agreement as all cash and cash equivalents on hand at the end of each quarter less reserves established by MGP in its reasonable discretion for future cash requirements. These reserves are retained to provide for the conduct of our business, the payment of debt principal and interest and to provide funds for future distributions. Prior to the Exchange Transaction in July 2017 (See Note 1 – Organization and Presentation – Partnership Simplification), as quarterly distributions of available cash exceeded certain target distribution levels, MGP received incentive distributions based on specified increasing percentages of the available cash that exceeded the target distribution levels. MGP was entitled to receive 15% of the amount we distributed in excess of $0.1375 per unit, 25% of the amount we distributed in excess of $0.15625 per unit, and 50% of the amount we distributed in excess of $0.1875 per unit. During the year ended December 31, 2017, we paid to MGP incentive distributions of $37.6 million. Beginning with distributions paid in the third quarter of 2017, we no longer make distributions with respect to the IDRs. The following table summarizes the quarterly per unit distribution paid during the respective quarter: Year Ended December 31, 2019 2018 2017 First Quarter $ 0.5300 $ 0.5100 $ 0.4375 Second Quarter $ 0.5350 $ 0.5150 $ 0.4375 Third Quarter $ 0.5400 $ 0.5200 $ 0.5000 Fourth Quarter $ 0.5400 $ 0.5250 $ 0.5050 On January 27, 2020, we declared a quarterly distribution of $0.40 per unit, totaling approximately $50.8 million, on all our common units outstanding paid Exchange Transaction On July 28, 2017, as part of the Exchange Transaction discussed in Note 1 – Organization and Presentation – Partnership Simplification, MGP contributed to ARLP all of its IDRs and its 0.99% managing general partner interest in ARLP in exchange for 56,100,000 ARLP common units and a non-economic general partner interest in ARLP. In conjunction with this transaction and on the same economic basis as MGP, SGP also contributed to ARLP its 0.01% general partner interests in both ARLP and the Intermediate Partnership in exchange for 28,141 ARLP common units. The Exchange Transaction constituted an exchange of equity interests between entities under common control and not a transfer of a business. Therefore, the exchange resulted in a reclassification, as of the date of the Exchange Transaction, of a $306.7 million deficit capital balance from the General Partners' interest Limited Partners - Common Unitholders 1999 Simplification Transactions On May 31, 2018, as part of the Simplification Transactions discussed in Note 1 – Organization and Presentation, ARLP issued 1,322,388 ARLP common units to the Owners of SGP in exchange for causing SGP to contribute to ARLP all of SGP's limited partner interests in AHGP, which included AHGP's indirect ownership of a 1.0001% general partner interest in the Intermediate Partnership and a 0.001% managing member interest in Alliance Coal. The Simplification Transactions are accounted for prospectively as an exchange of equity interests between entities under common control. Since ARLP and AHGP were under common control both before and after the Simplification Transactions, no fair value adjustment was made to the assets or liabilities of AHGP and its subsidiaries and no gain or loss was recognized on our consolidated financial statements. Unit Repurchase Program In May 2018, the Board of Directors approved the establishment of a unit repurchase program authorizing us to repurchase and retire up to $100 million of ARLP common units. The program has no time limit and we may repurchase units from time to time in the open market or in other privately negotiated transactions. The unit repurchase program authorization does not obligate us to repurchase any dollar amount or number of units. As of December 31, 2019, we had repurchased and retired 5,460,639 units at an average unit price of $17.12 for an aggregate purchase price of $93.5 million. Total units repurchased includes the repurchase and retirement of 35 units representing fractional units as part of the Simplification Transactions which are not part of the unit repurchase program. Affiliated Entity Contributions An affiliated entity controlled by Mr. Craft made capital contributions of $2.1 million and $1.0 million during the years ended December 31, 2018 and 2017, respectively, for the purpose of funding certain general and administrative expenses. On June 29, 2018, the members of this affiliated entity contributed 467,018 ARLP common units for similar purposes. Other The noncontrolling interest in our consolidated balance sheets represents Bluegrass Minerals' ownership interest in Cavalier Minerals. Our accumulated other comprehensive loss consists of unrecognized actuarial gains and losses as well as unrecognized prior service costs related to our pension and pneumoconiosis benefits. See Note 11 – Variable Interest Entities, Note 15 –Employee Benefit Plans and Note 19 – Accrued Workers' Compensation and Pneumoconiosis Benefits for further information.

VARIABLE INTEREST ENTITIES

VARIABLE INTEREST ENTITIES	12 Months Ended
VARIABLE INTEREST ENTITIES	Dec. 31, 2019
VARIABLE INTEREST ENTITIES
VARIABLE INTEREST ENTITIES	11. VARIABLE INTEREST ENTITIES Cavalier Minerals On November 10, 2014, our subsidiary, Alliance Minerals, and Bluegrass Minerals entered into a limited liability company agreement (the "Cavalier Agreement") to create Cavalier Minerals, which was formed to indirectly acquire oil & gas mineral interests through its ownership in AllDale I & II. Alliance Minerals owns a 96% membership interest in Cavalier Minerals, and Bluegrass Minerals owns a 4% membership interest in Cavalier Minerals and a profits interest which entitles it to receive distributions equal to 25% of all distributions (including in liquidation) after all members have recovered their investment. Distributions with respect to Bluegrass Minerals' profits interest will be offset by all distributions received by Bluegrass Minerals from the former general partners of AllDale I & II. To date, there has been no profits interest distributions. Bluegrass Minerals was Cavalier Minerals' managing member prior to the AllDale Acquisition (see Note 3 – Acquisitions). In conjunction with the AllDale Acquisition, we became the managing member in Cavalier Minerals. Total contributions to and cumulative distributions from Cavalier Minerals are as follows: Alliance Bluegrass Minerals Minerals (in thousands) Contributions $ 143,112 $ 5,963 Distributions 71,916 2,996 We have concluded that Cavalier Minerals is a VIE which we consolidate as the primary beneficiary because we are the managing member and a substantial equity owner in Cavalier Minerals. Bluegrass Minerals' equity ownership of Cavalier Minerals is accounted for as noncontrolling ownership interest in our consolidated balance sheets. In addition, earnings attributable to Bluegrass Minerals are recognized as noncontrolling interest in our consolidated statements of income. AllDale III In February 2017, Alliance Minerals committed to directly invest $30.0 million in AllDale III which was created for similar investment purposes as AllDale I & II. Alliance Minerals completed funding of this commitment in 2018. Alliance Minerals' limited partner interest in AllDale III at December 31, 2019 was 13.9%. The AllDale III Partnership Agreement includes a 25% profits interest for the general partner, subject to a return hurdle equal to the greater of 125% of cumulative capital contributions and a 10% internal rate of return, and following an 80/20 "catch-up" provision for the general partner. Since AllDale III is structured as a limited partnership with the limited partners 1) not having the ability to remove the general partner and 2) not participating significantly in the operational decisions, we concluded that AllDale III is a VIE. We are not the primary beneficiary of AllDale III as we do not have the power to direct the activities that most significantly impact AllDale III's economic performance. We account for our ownership interest in the income or loss of AllDale III as an equity method investment. We record equity income or loss based on AllDale III's distribution structure. See Note 12 – Investments for more information. WKY CoalPlay On November 17, 2014, SGP Land, LLC ("SGP Land"), a wholly owned subsidiary of SGP, and two limited liability companies ("Craft Companies") owned by irrevocable trusts established by the Chairman, President and CEO of MGP and his children entered into a limited liability company agreement to form WKY CoalPlay, LLC ("WKY CoalPlay"). WKY CoalPlay was formed, in part, to purchase and lease coal reserves. WKY CoalPlay is managed by an individual who is an officer and director of Alliance Resource Holdings II, Inc. ("ARH II") and trustee of the irrevocable trusts owning one of the Craft Companies. In December 2014 and February 2015, we entered into various coal reserve leases with WKY CoalPlay. See Note 20 – Related-Party Transactions for further information on our lease terms with WKY CoalPlay. We have concluded that WKY CoalPlay is a VIE because of our ability to exercise options to acquire reserves under lease with WKY CoalPlay (Note 20 – Related-Party Transactions), which is not within the control of the equity holders and, if it occurs, could potentially limit the expected residual return to the owners of WKY CoalPlay. We do not have any economic or governance rights related to WKY CoalPlay and our options that provide us with a variable interest in WKY CoalPlay's reserve assets do not give us any rights that constitute power to direct the primary activities that most significantly impact WKY CoalPlay's economic performance. SGP Land has the sole ability to replace the manager of WKY CoalPlay at its discretion and therefore has power to direct the activities of WKY CoalPlay. Consequently, we concluded that SGP Land is the primary beneficiary of WKY CoalPlay. See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for variable interest entities.

INVESTMENTS

INVESTMENTS	12 Months Ended
INVESTMENTS	Dec. 31, 2019
INVESTMENTS
INVESTMENTS	12. INVESTMENTS AllDale III As discussed in Note 11 – Variable Interest Entities, we account for our ownership interest in the income or loss of AllDale III as an equity method investment. We record equity income or loss based on AllDale III's distribution structure. The changes in our equity method investment in AllDale III for each of the periods presented were as follows: Year Ended December 31, 2019 2018 2017 (in thousands) Beginning balance $ 28,974 $ 14,182 $ — Contributions — 15,600 14,400 Equity method investment income (loss) 2,203 547 (218) Distributions received (2,648) (1,355) — Ending balance $ 28,529 $ 28,974 $ 14,182 Kodiak On July 19, 2017, Alliance Minerals purchased $100 million of Series A-1 Preferred Interests from Kodiak, a privately-held company providing large-scale, high-utilization gas compression assets to customers operating primarily in the Permian Basin. This structured investment provided us with a quarterly cash or payment-in-kind return. On February 8, 2019, Kodiak redeemed our preferred interest for $135.0 million in cash resulting in an $11.5 million gain due to an early redemption premium. The gain is included in the Equity securities income See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for investments.

REVENUE FROM CONTRACTS WITH CUS

REVENUE FROM CONTRACTS WITH CUSTOMERS	12 Months Ended
REVENUE FROM CONTRACTS WITH CUSTOMERS	Dec. 31, 2019
REVENUE FROM CONTRACTS WITH CUSTOMERS
REVENUE FROM CONTRACTS WITH CUSTOMERS	13. REVENUE FROM CONTRACTS WITH CUSTOMERS The following table illustrates the disaggregation of our revenues by type, including a reconciliation to our segment presentation as presented in Note 23 – Segment Information. Illinois Other and Basin Appalachia Minerals Corporate Elimination Consolidated (in thousands) Year Ended December 31, 2019 Coal sales $ 1,128,588 $ 628,406 $ — $ 22,138 $ (16,690) $ 1,762,442 Oil & gas royalties — — 51,735 — — 51,735 Transportation revenues 94,686 4,817 — — — 99,503 Other revenues 13,034 11,166 1,301 34,712 (12,173) 48,040 Total revenues $ 1,236,308 $ 644,389 $ 53,036 $ 56,850 $ (28,863) $ 1,961,720 Year Ended December 31, 2018 Coal sales $ 1,197,143 $ 635,530 $ — $ 43,393 $ (31,258) $ 1,844,808 Transportation revenues 106,947 5,435 — 3 — 112,385 Other revenues 16,999 3,000 — 38,096 (12,431) 45,664 Total revenues $ 1,321,089 $ 643,965 $ — $ 81,492 $ (43,689) $ 2,002,857 Year Ended December 31, 2017 Coal sales $ 1,078,255 $ 616,305 $ — $ 74,973 $ (58,419) $ 1,711,114 Transportation revenues 35,585 6,115 — — — 41,700 Other revenues 12,024 3,621 — 39,776 (12,015) 43,406 Total revenues $ 1,125,864 $ 626,041 $ — $ 114,749 $ (70,434) $ 1,796,220 The following table illustrates the amount of our transaction price for all current coal supply contracts allocated to performance obligations that are unsatisfied or partially unsatisfied as of December 31, 2019 and disaggregated by segment and contract duration. 2023 and 2020 2021 2022 Thereafter Total (in thousands) Illinois Basin coal revenues $ 849,040 $ 437,808 $ 34,414 $ 8,470 $ 1,329,732 Appalachia coal revenues 426,162 97,729 54,132 — 578,023 Total coal revenues (1) $ 1,275,202 $ 535,537 $ 88,546 $ 8,470 $ 1,907,755 (1) Coal revenues generally consists of consolidated revenues excluding our Minerals segment.

EARNINGS PER LIMITED PARTNER UN

EARNINGS PER LIMITED PARTNER UNIT	12 Months Ended
EARNINGS PER LIMITED PARTNER UNIT	Dec. 31, 2019
EARNINGS PER LIMITED PARTNER UNIT
EARNINGS PER LIMITED PARTNER UNIT	14. EARNINGS PER LIMITED PARTNER UNIT We utilize the two-class method in calculating basic and diluted earnings per limited partner unit ("EPU"). Subsequent to the Simplification Transactions, net income attributable to ARLP is only allocated to limited partners and participating securities under deferred compensation plans. Prior to the Simplification Transactions, net income attributable to ARLP was allocated to the general partners, limited partners and participating securities under deferred compensation plans in accordance with their respective partnership ownership percentages, after giving effect to any special income or expense allocations. Prior to the Exchange Transaction, net income attributable to ARLP was also allocated to our general partner, MGP, for incentive distributions. Please see Note 1 – Organization and Presentation for more information on the Simplification Transactions and the Exchange Transaction. Our participating securities under deferred compensation plans include rights to nonforfeitable distributions or distribution equivalents. Our participating securities are outstanding awards under our LTIP and phantom units in notional accounts under our SERP and the Directors' Deferred Compensation Plan. In connection with the Exchange Transaction, ARLP amended its partnership agreement to reflect, among other things, cancellation of the IDRs and the economic general partner interest in ARLP and issuance of a non-economic general partner interest to MGP. The IDR provisions of our partnership agreement prior to the Exchange Transaction are outlined in Note 10 – Partners' Capital. Beginning with distributions declared for the three months ended June 30, 2017, we no longer make distributions with respect to the IDRs. As a result of the Simplification Transactions, MGP no longer holds economic interests in the Intermediate Partnership or Alliance Coal. We no longer make distributions or allocate income and losses to MGP in our calculation of EPU. The following is a reconciliation of net income attributable to ARLP used for calculating basic and diluted earnings per unit and the weighted-average units used in computing EPU. Year Ended December 31, 2019 2018 2017 (in thousands, except per unit data) Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Adjustments: MGP's priority distributions (1) — — (19,216) General partners' equity ownership (1) — (1,560) (3,688) General partner's special allocation of certain general and administrative expenses (2) — — 1,000 Limited partners' interest in net income attributable to ARLP 399,414 365,044 281,734 Less: Distributions to participating securities (4,254) (5,114) (4,339) Undistributed earnings attributable to participating securities (2,237) (1,641) (1,026) Net income attributable to ARLP available to limited partners $ 392,923 $ 358,289 $ 276,369 Weighted-average limited partner units outstanding – basic and diluted 128,117 130,758 98,708 Earnings per limited partner unit - basic and diluted (3) $ 3.07 $ 2.74 $ 2.80 (1) Amounts for 2019 and 2018 reflect the impact of the Simplification Transactions which ended net income allocations and quarterly cash distributions to MGP after May 31, 2018. Amounts for 2017 reflect the impact of the Exchange Transaction ending distributions that would have been paid for the IDRs and a 0.99% general partner interest in ARLP, both of which were held by MGP prior to the 2017 Exchange Transaction. For the time period between the Exchange Transaction and the Simplification Transactions, MGP maintained a 1.0001% general partner interest in the Intermediate Partnership and a 0.001% managing member interest in Alliance Coal and thus received quarterly distributions and income and loss allocations during this time period. The SGP had a nominal general partner interest prior to the Exchange Transaction. (2) MGP made a capital contribution of $1.0 million during 2017 to Alliance Coal for the purpose of funding certain general and administrative expenses. As provided under our partnership agreement, we made a special allocation to MGP of certain general and administrative expenses equal to its contribution. Net income attributable to ARLP allocated to the limited partners was not burdened by this expense. See Note 10 – Partners' Capital for more information regarding this contribution. (3) Diluted EPU gives effect to all potentially dilutive common units outstanding during the period using the treasury stock method. Diluted EPU excludes all potentially dilutive units calculated under the treasury stock method if their effect is anti-dilutive. For the years ended December 31, 2019, 2018 and 2017, the combined total of LTIP, SERP and Directors' Deferred Compensation Plan units of 1,284,013 , 1,658,908 and 1,466,404 , respectively, were considered anti-dilutive under the treasury stock method. On a pro forma basis, as if the Exchange Transaction and the Simplification Transactions had taken place on January 1, 2017, the reconciliation of net income attributable to ARLP to basic and diluted earnings per unit and the weighted-average units used in computing EPU are as follows: Year Ended December 31, 2019 2018 2017 (in thousands, except per unit data) Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Pro forma adjustments (1) — (1,265) (1,943) Pro forma net income of ARLP 399,414 365,339 301,695 Less: Distributions to participating securities (4,254) (5,114) (4,339) Undistributed earnings attributable to participating securities (2,237) (1,627) (680) Net income attributable to ARLP available to limited partners (2) $ 392,923 $ 358,598 $ 296,676 Weighted-average limited partner units outstanding – basic and diluted (2) 128,117 131,310 132,024 Pro forma earnings per limited partner unit - basic and diluted (3) $ 3.07 $ 2.73 $ 2.25 (1) Pro forma adjustments to net income attributable to ARLP primarily represent the elimination of administrative service revenues from AHGP and the inclusion of general and administrative expenses incurred at AHGP. (2) Net income attributable to ARLP available to limited partners reflects net income allocations made for all periods presented based on the ownership structure subsequent to the Simplification Transactions. Accordingly, no general partner income allocations are presented above. Pro forma amounts above also reflect weighted average units outstanding as if the issuance of 56,128,141 ARLP common units in the Exchange Transaction and 1,322,388 ARLP common units in the Simplification Transactions applied to all periods presented. (3) Diluted EPU gives effect to all potentially dilutive common units outstanding during the period using the treasury stock method. Diluted EPU excludes all potentially dilutive units calculated under the treasury stock method if their effect is anti-dilutive. For the years ended December 31, 2019, 2018 and 2017, the combined total of LTIP, SERP and Directors' Deferred Compensation Plan units of 1,284,013 , 1,658,908 and 1,466,404 , respectively, were considered anti-dilutive under the treasury stock method. .

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
EMPLOYEE BENEFIT PLANS	Dec. 31, 2019
EMPLOYEE BENEFIT PLANS
EMPLOYEE BENEFIT PLANS	15. EMPLOYEE BENEFIT PLANS Defined Contribution Plans Defined Benefit Plan The following sets forth changes in benefit obligations and plan assets for the years ended December 31, 2019 and 2018 and the funded status of the Pension Plan reconciled with the amounts reported in our consolidated financial statements: December 31, 2019 2018 (dollars in thousands) Change in benefit obligations: Benefit obligations at beginning of year $ 118,958 $ 127,298 Interest cost 4,864 4,462 Actuarial loss (gain) 17,084 (8,562) Benefits paid (4,481) (4,240) Benefit obligations at end of year 136,425 118,958 Change in plan assets: Fair value of plan assets at beginning of year 75,823 81,981 Employer contribution 5,559 4,187 Actual return on plan assets 14,666 (6,105) Benefits paid (4,481) (4,240) Fair value of plan assets at end of year 91,567 75,823 Funded status at the end of year $ (44,858) $ (43,135) Amounts recognized in balance sheet: Non-current liability $ (44,858) $ (43,135) Amounts recognized in accumulated other comprehensive income consists of: Prior service cost $ (940) $ (1,126) Net actuarial loss (45,125) (41,697) $ (46,065) $ (42,823) Weighted-average assumption to determine benefit obligations as of December 31, Discount rate 3.15% 4.17% Weighted-average assumptions used to determine net periodic benefit cost for the year ended December 31, Discount rate 4.17% 3.54% Expected return on plan assets 6.50% 7.00% The actuarial loss component of the change in benefit obligation in 2019 was primarily attributable to a decrease in the discount rate compared to December 31, 2018, offset in part by updated mortality tables. The actuarial gain component of the change in benefit obligation in 2018 was primarily attributable to an increase in the discount rate compared to December 31, 2017 and updated mortality tables, offset in part by decreases in expected retirements and other demographic changes. The expected long-term rate of return used to determine our pension liability is based on a 1.5% active management premium in addition to an asset allocation assumption of: Asset allocation As of December 31, 2019 assumption Equity securities 62% Fixed income securities 33% Real estate 5% 100% The actual return on plan assets was 19.2% and a loss of 6.7% for the years ended December 31, 2019 and 2018, respectively. Year Ended December 31, 2019 2018 2017 (in thousands) Components of net periodic benefit cost: Interest cost $ 4,864 $ 4,462 $ 4,587 Expected return on plan assets (4,932) (5,784) (4,978) Amortization of prior service cost 186 186 186 Amortization of net loss 3,922 3,608 3,054 Net periodic benefit cost (1) $ 4,040 $ 2,472 $ 2,849 (1) Nonservice components of net periodic benefit cost are included in the Other income (expense) line item within our consolidated statements of income (see Note 2 – Summary of Significant Accounting Policies ). Year Ended December 31, 2019 2018 (in thousands) Other changes in plan assets and benefit obligation recognized in accumulated other comprehensive loss: Net actuarial loss $ (7,350) $ (3,326) Reversal of amortization item: Prior service cost 186 186 Net actuarial loss 3,922 3,608 Total recognized in accumulated other comprehensive loss (3,242) 468 Net periodic benefit cost (4,040) (2,472) Total recognized in net periodic benefit cost and accumulated other comprehensive loss $ (7,282) $ (2,004) Estimated future benefit payments as of December 31, 2019 are as follows: Year Ended December 31, (in thousands) 2020 $ 5,288 2021 5,677 2022 6,045 2023 6,342 2024 6,507 2025-2029 34,755 $ 64,614 We expect to contribute $5.3 million to the Pension Plan in 2020. The Compensation Committee has appointed an investment manager with full investment authority with respect to Pension Plan investments subject to investment guidelines and compliance with ERISA or other applicable laws. The investment manager employs a series of asset allocation strategy phases to glide the portfolio risk commensurate with both plan characteristics and market conditions. The objective of the allocation policy is to reach and maintain fully funded status. The total portfolio allocation will be adjusted as the funded ratio of the Pension Plan changes and market conditions warrant. The target allocation includes investments in equity and fixed income commingled investment funds. Total account performance is reviewed at least annually, using a dynamic benchmark approach to track investment performance. General asset allocation guidelines at December 31, 2019 are as follows: Percentage of Total Portfolio Minimum Target Maximum Equity securities 45% 62% 80% Fixed income securities 10% 33% 55% Real estate 0% 5% 10% Equity securities include domestic equity securities, developed international securities, emerging markets equity securities and real estate investment trust. Fixed income securities include domestic and international investment grade fixed income securities, high yield securities and emerging markets fixed income securities. Fixed income futures may also be utilized within the fixed income securities asset allocation. The following information discloses the fair values of our Pension Plan assets by asset category: December 31, 2019 2018 (in thousands) Cash and cash equivalents (a) $ 2,958 $ 5,277 Commingled investment funds measured at net asset value (b): Equities - Global 10,028 — Equities - United States large-cap 19,220 21,862 Equities - United States small-cap 7,592 5,259 Equities - International developed markets 10,528 10,593 Equities - International emerging markets 8,410 4,808 Fixed income - Investment grade 26,186 15,777 Fixed income - High yield — 4,508 Real estate 4,355 5,034 Other 2,290 2,705 Total $ 91,567 $ 75,823 (a) Cash and cash equivalents represents a Level 1 fair value measurement. See Note 2 – Summary of Significant Accounting Policies – Fair Value Measurements for more information regarding the definitions of fair value hierarchy levels. (b) Investments measured at fair value using the net asset value per share (or its equivalent) have not been classified within the fair value hierarchy. The fair values of all commingled investment funds are determined based on the net asset values per unit of each of the funds. The net asset values per unit represent the aggregate value of the fund's assets at fair value less liabilities, divided by the number of units outstanding. See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for pension benefits.

COMPENSATION PLANS

COMPENSATION PLANS	12 Months Ended
COMPENSATION PLANS	Dec. 31, 2019
COMPENSATION PLANS
COMPENSATION PLANS	16. COMPENSATION PLANS Long-Term Incentive Plan We maintain the LTIP for certain employees and officers of MGP and its affiliates who perform services for us. The LTIP awards are grants of non-vested "phantom" or notional units, also referred to as "restricted units", which upon satisfaction of time and performance-based vesting requirements, entitle the LTIP participant to receive ARLP common units. Annual grant levels and vesting provisions for designated participants are recommended by the Chairman, President and CEO of MGP, subject to review and approval of the Compensation Committee. Vesting of all grants outstanding is subject to the satisfaction of certain financial tests, which management currently believes is probable. Grants issued to LTIP participants are expected to cliff vest on January 1st of the third year following issuance of the grants. We account for forfeitures of non-vested LTIP grants as they occur. We expect to settle the non-vested LTIP grants by delivery of ARLP common units, except for the portion of the grants that will satisfy employee tax withholding obligations of LTIP participants. As provided under the distribution equivalent rights ("DERs") provisions of the LTIP and the terms of the LTIP awards, all non-vested grants include contingent rights to receive quarterly distributions in cash or, at the discretion of the Compensation Committee, phantom units in lieu of cash credited to a bookkeeping account with value equal to the cash distributions we make to unitholders during the vesting period. A summary of non-vested LTIP grants is as follows: Number of units Weighted average grant date fair value per unit Intrinsic value (in thousands) Non-vested grants at January 1, 2017 1,604,748 $ 23.19 $ 36,027 Granted 475,310 23.17 Vested (1) (350,516) 40.73 Forfeited (35,516) 20.01 Non-vested grants at December 31, 2017 1,694,026 19.62 33,372 Granted 511,305 20.40 Vested (1) (331,502) 34.61 Forfeited (45,749) 17.40 Non-vested grants at December 31, 2018 1,828,080 17.18 31,699 Granted 682,155 18.63 Vested (1) (885,381) 12.38 Forfeited (21,476) 20.84 Non-vested grants at December 31, 2019 1,603,378 20.39 17,349 (1) During the years ended December 31, 2019, 2018 and 2017, we issued 596,650 , 191,858 and 222,011 , respectively, unrestricted common units to the LTIP participants. The remaining vested units were settled in cash primarily to satisfy tax withholding obligations of the LTIP participants. For the years ended December 31, 2019, 2018 and 2017, our LTIP expense was $10.4 million, $10.8 million and $11.0 million, respectively. The total obligation associated with the LTIP as of December 31, 2019 and 2018 was $20.2 million and $20.8 million, respectively, and is included in the partners' capital Limited partners-common unitholders On January 22, 2020, the Compensation Committee determined that the vesting requirements for the 2017 grants of 424,486 restricted units (which was net of 50,824 forfeitures and previously settled units) had been satisfied as of January 1, 2020. As a result of this vesting, on February 10, 2020, we issued 279,622 unrestricted common units to the LTIP participants. The remaining units were settled in cash to satisfy tax withholding obligations of the LTIP participants. On January 22, 2020, the Compensation Committee also authorized additional grants of 965,035 restricted units, of which 950,035 units were granted. After consideration of the January 1, 2020 vesting and subsequent issuance of 279,622 common units, approximately 1.0 million units remain available under the LTIP for issuance in the future, assuming all grants issued in 2020, 2019 and 2018 and currently outstanding are settled with common units, without reduction for tax withholding, no future forfeitures occur and DERs continue being paid in cash versus additional phantom units. Supplemental Executive Retirement Plan and Directors' Deferred Compensation Plan We utilize the SERP to provide deferred compensation benefits for certain officers and key employees. All allocations made to participants under the SERP are made in the form of "phantom" ARLP units and SERP distributions will be settled in the form of ARLP common units. The SERP is administered by the Compensation Committee. Our directors participate in the Directors' Deferred Compensation Plan. Pursuant to the Directors' Deferred Compensation Plan, for amounts deferred either automatically or at the election of the director, a notional account is established and credited with notional common units of ARLP, described in the Directors' Deferred Compensation Plan as "phantom" units. Distributions from the Directors' Deferred Compensation Plan will be settled in the form of ARLP common units. For both the SERP and Directors' Deferred Compensation Plan, when quarterly cash distributions are made with respect to ARLP common units, an amount equal to such quarterly distribution is credited to each participant's notional account as additional phantom units. All grants of phantom units under the SERP and Directors' Deferred Compensation Plan vest immediately. A summary of SERP and Directors' Deferred Compensation Plan activity is as follows: Number of units Weighted average grant date fair value per unit Intrinsic value (in thousands) Phantom units outstanding as of January 1, 2017 494,018 $ 29.77 $ 11,091 Granted 67,766 20.38 Phantom units outstanding as of December 31, 2017 561,784 28.64 11,067 Granted 84,417 18.78 Issued (1) (10,364) 27.92 Phantom units outstanding as of December 31, 2018 635,837 27.34 11,025 Granted 111,012 14.50 Issued (1) (115,484) 25.20 Phantom units outstanding as of December 31, 2019 631,365 25.48 6,831 (1) During the years ended December 31, 2019 and 2018, we issued ARLP common units of 115,484 and 7,181 , respectively, to participants under the SERP and Directors' Deferred Compensation Plan . Units issued in 2018 were net of units settled in cash to satisfy tax withholding obligations. Total SERP and Directors' Deferred Compensation Plan expense was $1.6 million, $1.6 million and $1.4 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019 and 2018, the total obligation associated with the SERP and Directors' Deferred Compensation Plan was $16.1 million and $17.4 million, respectively, and is included in the partners' capital Limited partners-common unitholders See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for unit-based compensation.

SUPPLEMENTAL CASH FLOW INFORMAT

SUPPLEMENTAL CASH FLOW INFORMATION	12 Months Ended
SUPPLEMENTAL CASH FLOW INFORMATION	Dec. 31, 2019
SUPPLEMENTAL CASH FLOW INFORMATION
SUPPLEMENTAL CASH FLOW INFORMATION	17. SUPPLEMENTAL CASH FLOW INFORMATION Year Ended December 31, 2019 2018 2017 (in thousands) Cash Paid For: Interest $ 43,093 $ 38,450 $ 31,692 Income taxes $ — $ 34 $ 210 Non-Cash Activity: Accounts payable for purchase of property, plant and equipment $ 14,504 $ 14,585 $ 15,636 Assets acquired by finance lease $ — $ 835 $ — Right-of-use assets acquired by operating lease $ 25,593 — — Market value of common units issued under deferred compensation plans before tax withholding requirements $ 17,415 $ 6,142 $ 8,149 Acquisition of businesses: Fair value of assets assumed $ 629,475 $ — $ — Previously held equity-method investments (1) (307,322) — — Cash paid, net of cash acquired (320,232) — — Fair value of liabilities assumed $ 1,921 $ — $ — (1) Inclusive of gain of $177.0 million as discussed in Note 3 – Acquisitions.

ASSET RETIREMENT OBLIGATIONS

ASSET RETIREMENT OBLIGATIONS	12 Months Ended
ASSET RETIREMENT OBLIGATIONS	Dec. 31, 2019
ASSET RETIREMENT OBLIGATIONS
ASSET RETIREMENT OBLIGATIONS	18. ASSET RETIREMENT OBLIGATIONS The majority of our operations are governed by various state statutes and the Federal Surface Mining Control and Reclamation Act of 1977, which establish reclamation and mine closing standards. These regulations require, among other things, restoration of property in accordance with specified standards and an approved reclamation plan. The following table presents the activity affecting the asset retirement and mine closing liability: Year Ended December 31, 2019 2018 (in thousands) Beginning balance $ 137,114 $ 130,600 Accretion expense 4,087 3,926 Payments (2,948) (2,392) Allocation of liability associated with acquisitions, mine development and change in assumptions (739) 4,980 Ending balance $ 137,514 $ 137,114 For the year ended December 31, 2019, the allocation of liability associated with acquisition, mine development and change in assumptions was immaterial. For the year ended December 31, 2018, the allocation of liability associated with acquisition, mine development and change in assumptions was a net increase of $5.0 million. This net increase was attributable to the expansion of refuse sites primarily at the Hamilton County Coal, LLC ("Hamilton") and Tunnel Ridge, LLC ("Tunnel Ridge") mines, partially offset by decreased cost estimates for water related treatment at the Mettiki mine and completion of certain reclamation obligations at the Hopkins County Coal mining complex. The impact of discounting our estimated cash flows resulted in reducing the accrual for asset retirement obligations by $102.9 million and $100.3 million at December 31, 2019 and 2018, respectively. Estimated payments of asset retirement obligations as of December 31, 2019 are as follows: Year Ended December 31, (in thousands) 2020 $ 4,496 2021 2,576 2022 2,794 2023 2,027 2024 2,986 Thereafter 225,584 Aggregate undiscounted asset retirement obligations 240,463 Effect of discounting (102,949) Total asset retirement obligations 137,514 Less: current portion (4,496) Asset retirement obligations $ 133,018 Federal and state laws require bonds to secure our obligations to reclaim lands used for mining and are typically renewable on a yearly basis. As of December 31, 2019 and 2018, we had approximately $181.6 million and $169.3 million, respectively, in surety bonds outstanding to secure the performance of our reclamation obligations. See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for asset retirement obligations.

ACCRUED WORKERS' COMPENSATION A

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS	12 Months Ended
ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS	Dec. 31, 2019
ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS
ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS	19. ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS We provide income replacement and medical treatment for work-related traumatic injury claims as required by applicable state laws. Workers' compensation laws also compensate survivors of workers who suffer employment related deaths. Certain of our mine operating entities are liable under state statutes and the Federal Coal Mine Health and Safety Act of 1969, as amended, to pay benefits for black lung disease (or pneumoconiosis) to eligible employees and former employees and their dependents. Both pneumoconiosis and traumatic claims are covered through our self-insured programs. The following is a reconciliation of the changes in workers' compensation liability (including current and long-term liability balances): December 31, 2019 2018 (in thousands) Beginning balance $ 49,539 $ 54,439 Accruals increase 7,162 7,654 Payments (11,320) (10,837) Interest accretion 1,606 1,454 Valuation loss (gain) 6,397 (3,171) Ending balance $ 53,384 $ 49,539 The discount rate used to calculate the estimated present value of future obligations for workers' compensation was 2.81% and 3.89% at December 31, 2019 and 2018, respectively. The 2019 valuation loss was primarily attributable to a decrease in the discount rate used to calculate the estimated present value of future obligations as well as unfavorable changes in claims development. The 2018 valuation gain was primarily attributable to an increase in the discount rate used to calculate the estimated present value of future obligations as well as favorable changes in claims development. As of December 31, 2019 and 2018, we had $90.2 million and $90.5 million, respectively, in surety bonds and letters of credit outstanding to secure workers' compensation obligations. We limit our exposure to traumatic injury claims by purchasing a high deductible insurance policy that starts paying benefits after deductibles for the particular claim year have been met. Our workers' compensation liability above is presented on a gross basis and does not include our expected receivables on our insurance policy. Our receivables for traumatic injury claims under this policy as of December 31, 2019 and 2018 are $7.7 million and $8.1 million, respectively. Our receivables are included in Other long-term assets The following is a reconciliation of the changes in pneumoconiosis benefit obligations: December 31, 2019 2018 (in thousands) Benefit obligations at beginning of year $ 72,095 $ 74,859 Service cost 2,593 2,525 Interest cost 3,044 2,542 Actuarial (gain) loss 23,298 (4,599) Benefits and expenses paid (3,347) (3,232) Benefit obligations at end of year $ 97,683 $ 72,095 The following is a reconciliation of the changes in the pneumoconiosis benefit obligation recognized in accumulated other comprehensive loss: Year Ended December 31, 2019 2018 2017 (in thousands) Net actuarial gain (loss) $ (23,298) $ 4,599 $ (7,938) Reversal of amortization item: Net actuarial (gain) loss (4,582) 2 (2,092) Total recognized in accumulated other comprehensive loss $ (27,880) $ 4,601 $ (10,030) The discount rate used to calculate the estimated present value of future obligations for pneumoconiosis benefits was 3.12%, 4.13% and 3.49% at December 31, 2019, 2018 and 2017, respectively. Year Ended December 31, 2019 2018 2017 (in thousands) Amount recognized in accumulated other comprehensive loss consists of: Net actuarial loss $ 31,927 $ 4,047 $ 8,648 The actuarial loss component of the change in benefit obligations in 2019 was primarily attributable to a) a decrease in the discount rate used to calculate the estimated present value of the future obligations and b) an increase in Federal and State benefit levels. These components were offset in part by favorable demographic changes in the at-risk population. The actuarial gain component of the change in benefit obligations in 2018 was primarily attributable to a) an increase in the discount rate used to calculate the estimated present value of the future obligations, b) a decrease in the assumed future medical benefit and expense levels and c) demographic changes in the at-risk population. Summarized below is information about the amounts recognized in the accompanying consolidated balance sheets for pneumoconiosis and workers' compensation benefits: December 31, 2019 2018 (in thousands) Workers’ compensation claims $ 53,384 $ 49,539 Pneumoconiosis benefit claims 97,683 72,095 Total obligations 151,067 121,634 Less current portion (11,175) (11,137) Non-current obligations $ 139,892 $ 110,497 Both the pneumoconiosis benefit and workers' compensation obligations were unfunded at December 31, 2019 and 2018. The pneumoconiosis benefit and workers' compensation expense consists of the following components: Year Ended December 31, 2019 2018 2017 (in thousands) Black lung benefits: Service cost $ 2,593 $ 2,525 $ 2,255 Interest cost (1) 3,044 2,542 2,555 Net amortization (1) (4,582) 2 (2,092) Total pneumoconiosis expense 1,055 5,069 2,718 Workers' compensation expense 17,541 11,270 12,215 Net periodic benefit cost $ 18,596 $ 16,339 $ 14,933 ________________________________________ (1) Interest cost and net amortization is included in the Other income (expense) line item within our consolidated statements of income ( see Note 2 – Summary of Significant Accounting Policies). See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for workers' compensation and pneumoconiosis benefits.

RELATED-PARTY TRANSACTIONS

RELATED-PARTY TRANSACTIONS	12 Months Ended
RELATED-PARTY TRANSACTIONS	Dec. 31, 2019
RELATED-PARTY TRANSACTIONS
RELATED-PARTY TRANSACTIONS	20. RELATED-PARTY TRANSACTIONS We have continuing related-party transactions with MGP and its affiliates. The Board of Directors and its Conflicts Committee review our related-party transactions that involve a potential conflict of interest between our general partner or its affiliates and ARLP or its subsidiaries or any other partner of ARLP to determine that such transactions are fair and reasonable to ARLP. As a result of these reviews, the Board of Directors and the Conflicts Committee approved each of the transactions described below that had such potential conflict of interest as fair and reasonable to ARLP. Affiliate Coal Lease Agreements The following table summarizes advanced royalties outstanding and related payments and recoupments under our affiliate coal lease agreements: WKY CoalPlay Towhead Webster Henderson WKY SGP/Craft Foundations Coal Coal Coal CoalPlay Henderson Henderson Tunnel & Union Webster Henderson & Union Ridge Counties, KY County, KY County, KY Counties, KY Total Acquired Acquired Acquired Acquired Acquired 2005 December 2014 December 2014 December 2014 February 2015 (in thousands) As of January 1, 2017 — 7,195 3,319 5,044 4,262 19,820 Payments 6,000 3,598 2,568 2,522 2,131 16,819 Recoupment (3,000) (109) (531) — (6) (3,646) As of December 31, 2017 3,000 10,684 5,356 7,566 6,387 32,993 Payments — 3,597 2,570 2,520 2,131 10,818 Recoupment (3,000) (204) (31) — (36) (3,271) Unrecoupable — — (7,895) — — (7,895) As of December 31, 2018 — 14,077 — 10,086 8,482 32,645 Payments 4,500 3,597 2,568 2,521 2,131 15,317 Recoupment (3,000) (1,071) — — (107) (4,178) Unrecoupable — — (2,568) — — (2,568) As of December 31, 2019 1,500 16,603 — 12,607 10,506 41,216 SGP/Craft Foundations — one WKY CoalPlay — In December 2014, WKY CoalPlay's subsidiaries, Towhead Coal Reserves, LLC and Henderson Coal Reserves, LLC entered into coal lease agreements with Alliance Resource Properties. The leases have initial terms of 20 years and provide for earned royalty payments of 4.0% of the coal sales price to both and annual minimum royalty payments of $3.6 million and $2.5 million, respectively. All annual minimum royalty payments for each agreement are recoupable from future earned royalties related to their respective agreements. Each agreement grants Alliance Resource Properties an option to acquire the leased reserves at any time during a three-year period beginning in December 2017 for a purchase price that would provide WKY CoalPlay a 7.0% internal rate of return on its investment in the reserves taking into account payments previously made under the leases (See Note 11 – Variable Interest Entities). In December 2014, WKY CoalPlay's subsidiary, Webster Coal Reserves, LLC entered into a coal lease agreement with Alliance Resource Properties. The lease has an initial term of 7 years and provides for earned royalty payments of 4.0% of the coal sales price and annual minimum payments of $2.6 million. The agreement grants Alliance Resource Properties an option to acquire the leased reserves at any time during a three year period beginning in December 2017 for a purchase price that would provide WKY CoalPlay a 7.0% internal rate of return on its investment in the reserves taking into account payments previously made under the lease (See Note 11 – Variable Interest Entities). In the third quarter of 2019 it was determined that the balance of advanced royalties and the remaining future advance royalties payable in 2020 and 2021 totaling $5.1 million, may not be recouped as a result of the reduction of the Dotiki’s economic mine life determined in 2018 and the subsequent ceasing of production in the third quarter of 2019. We accrued the future advance payments and recognized the charge in Asset Impairment expense in the third quarter of 2019. See Note 4 – Long-Lived Asset Impairments for more information. Cavalier Minerals

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Dec. 31, 2019
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	21. COMMITMENTS AND CONTINGENCIES Commitments — Contractual Commitments — General Litigation — Various lawsuits, claims and regulatory proceedings incidental to our business are pending against the ARLP Partnership. We record an accrual for a potential loss related to these matters when, in management's opinion, such loss is probable and reasonably estimable. Based on known facts and circumstances, we believe the ultimate outcome of these outstanding lawsuits, claims and regulatory proceedings will not have a material adverse effect on our financial condition, results of operations or liquidity. However, if the results of these matters were different from management's current opinion and in amounts greater than our accruals, then they could have a material adverse effect. Other

CONCENTRATION OF CREDIT RISK AN

CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	12 Months Ended
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	Dec. 31, 2019
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS	22. CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS The international coal market has been a substantial part of our business with indirect sales to end users in Europe, Africa, Asia, North America and South America. Our sales into the international coal market are considered exports and are made through brokered transactions. During the years ended December 31, 2019, 2018 and 2017, export tons represented approximately 17.9%, 27.8% and 17.4% of tons sold, respectively. We use the end usage point as the basis for attributing tons to individual countries. Because title to our export shipments typically transfers to our brokerage customers at a point that does not necessarily reflect the end usage point, we attribute export tons to the country with the end usage point, if known. No individual country was attributed greater than 10% of total domestic and export tons sold during the years ended December 31, 2019, 2018 and 2017. We have significant long-term coal supply agreements, some of which contain prospective price adjustment provisions designed to reflect changes in market conditions, labor and other production costs and, in the infrequent circumstance when the coal is sold other than free on board the mine, changes in transportation rates. Our major customers are defined as those customers from which we derive at least ten percent of our total revenues, including transportation revenues. Total revenues from major customers are as follows: Year Ended December 31, Segment 2019 2018 2017 (in thousands) Customer A Illinois Basin $ 228,500 $ 219,115 $ — Customer B Appalachia 213,319 — — Trade accounts receivable from these customers totaled approximately $26.3 million at December 31, 2019. Trade accounts receivable from Customer A totaled approximately $12.8 million at December 31, 2018. Our bad debt experience has historically been insignificant. Financial conditions of our customers could result in a material change to our bad debt expense in future periods. The coal supply agreements with these customers expire in 2020 for Customer A and 2022 for Customer B.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
SEGMENT INFORMATION	Dec. 31, 2019
SEGMENT INFORMATION
SEGMENT INFORMATION	23. SEGMENT INFORMATION We operate in the United States as a diversified natural resource company that generates income from the production and marketing of coal to major domestic and international utilities and industrial users as well as income from oil & gas mineral interests. We aggregate multiple operating segments into three reportable segments, Illinois Basin, Appalachia, and Minerals. We also have an "all other" category referred to as Other and Corporate. Our two coal reportable segments correspond to major coal producing regions in the eastern United States with similar economic characteristics including coal quality, geology, coal marketing opportunities, mining and transportation methods and regulatory issues. The two coal segments include seven mining complexes operating in Illinois, Indiana, Kentucky, Maryland and West Virginia and a coal loading terminal in Indiana on the Ohio River. The Minerals reportable segment aggregates our oil & gas mineral interests which are located primarily in the Permian (Delaware and Midland), Anadarko (SCOOP/STACK) and Williston (Bakken) Basins. As discussed in Note 1 – Organization and Presentation, as a result of the AllDale Acquisition discussed in Note 3 – Acquisitions, we realigned our reportable segments in 2019 to include our oil & gas mineral interests within a new Minerals reportable segment and have recast prior periods to reflect that realignment. The Illinois Basin reportable segment includes our operating mining complexes (a) Gibson County Coal, LLC's mining complex, which includes the Gibson North and Gibson South mines, (b) Warrior Coal, LLC's mining complex, (c) River View's mining complex and (d) the Hamilton mining complex. The Illinois Basin reportable segment also includes our operating Mt. Vernon coal loading terminal in Indiana on the Ohio River. The Gibson North mine was idled in the fourth quarter of 2019 in response to market conditions. The Illinois Basin reportable segment also includes MAC and other support services as well as non-operating mining complexes (a) Webster County Coal, LLC's Dotiki mining complex, which ceased production in August 2019, (b) White County Coal, LLC's Pattiki mining complex, (c) the Hopkins County Coal mining complex, and (d) Sebree Mining, LLC's mining complex. The Appalachia reportable segment includes our operating mining complexes (a) the Mettiki mining complex, (b) the Tunnel Ridge mining complex and (c) the MC Mining mining complex. The Mettiki mining complex includes Mettiki Coal (WV), LLC's Mountain View mine and Mettiki Coal, LLC's preparation plant. The Appalachia reportable segment also includes the Penn Ridge reserves. The Minerals reportable segment includes oil & gas mineral interests held by AR Midland and AllDale I & II and includes Alliance Minerals' equity interests in both AllDale III (Note 12 – Investments) and Cavalier Minerals. AR Midland acquired its mineral interest in the Wing Acquisition (Note 3 – Acquisitions). Other and Corporate includes marketing and administrative activities, Matrix Design Group, LLC and its subsidiaries ("Matrix Design"), Alliance Design Group, LLC ("Alliance Design") (collectively, Matrix Design and Alliance Design referred to as the "Matrix Group"), Alliance Coal's coal brokerage activity and Alliance Minerals' prior equity investment in Kodiak. In February 2019, Kodiak redeemed our equity investment (see Note 12 – Investments). In addition, Other and Corporate includes certain Alliance Resource Properties' land and mineral interest activities, Pontiki Coal, LLC's workers' compensation and pneumoconiosis liabilities, Wildcat Insurance, which assists the ARLP Partnership with its insurance requirements, and AROP Funding and Alliance Finance (both discussed in Note 7 – Long-Term Debt). Reportable segment results are presented below. Illinois Other and Elimination Basin Appalachia Minerals Corporate (1) Consolidated (in thousands) Year Ended December 31, 2019 Revenues - Outside $ 1,219,618 $ 644,389 $ 53,036 $ 44,677 $ — $ 1,961,720 Revenues - Intercompany 16,690 — — 12,173 (28,863) — Total revenues (2) 1,236,308 644,389 53,036 56,850 (28,863) 1,961,720 Segment Adjusted EBITDA Expense (3) 756,423 423,623 7,811 36,845 (19,806) 1,204,896 Segment Adjusted EBITDA (4) 385,200 215,950 46,997 32,911 (9,057) 672,001 Total assets 1,373,516 500,027 643,213 541,261 (471,323) 2,586,694 Capital expenditures (5) 189,270 111,739 — 4,849 — 305,858 Year Ended December 31, 2018 Revenues - Outside $ 1,289,898 $ 643,898 $ — $ 69,061 $ — $ 2,002,857 Revenues - Intercompany 31,191 67 — 12,431 (43,689) — Total revenues (2) 1,321,089 643,965 — 81,492 (43,689) 2,002,857 Segment Adjusted EBITDA Expense (3) 796,370 398,243 — 52,321 (35,134) 1,211,800 Segment Adjusted EBITDA (4) 417,773 240,286 21,323 44,864 (8,555) 715,691 Total assets 1,380,912 440,518 161,312 589,010 (177,004) 2,394,748 Capital expenditures 166,468 64,037 — 2,975 — 233,480 Year Ended December 31, 2017 Revenues - Outside $ 1,069,767 $ 623,720 $ — $ 102,733 $ — $ 1,796,220 Revenues - Intercompany 56,097 2,321 — 12,016 (70,434) — Total revenues (2) 1,125,864 626,041 — 114,749 (70,434) 1,796,220 Segment Adjusted EBITDA Expense (3) 692,199 385,802 — 75,851 (61,665) 1,092,187 Segment Adjusted EBITDA (4) 398,080 234,124 13,297 45,296 (8,769) 682,028 Total assets 1,437,627 470,892 147,970 349,918 (187,036) 2,219,371 Capital expenditures 94,374 48,358 — 2,356 — 145,088 (1) The elimination column represents the elimination of intercompany transactions and is primarily comprised of sales from the Matrix Group to our mining operations, coal sales and purchases between operations within different segments, sales of receivables to AROP Funding, financing between segments and insurance premiums paid to Wildcat Insurance. (2) Revenues included in the Other and Corporate column are primarily attributable to the outside and affiliate revenues at the Matrix Group and coal brokerage activities. In additions, Other and Corporate includes affiliate revenues for administrative and Wildcat Insurance services. (3) Segment Adjusted EBITDA Expense includes operating expenses, coal purchases and other income. Transportation expenses are excluded as transportation revenues are recognized in an amount equal to transportation expenses when title passes to the customer. The following is a reconciliation of consolidated Segment Adjusted EBITDA Expense to Operating expenses (excluding depreciation, depletion and amortization) Year Ended December 31, 2019 2018 2017 (in thousands) Segment Adjusted EBITDA Expense $ 1,204,896 $ 1,211,800 $ 1,092,187 Outside coal purchases (23,357) (1,466) — Other income (expense) 561 (2,621) (332) Operating expenses (excluding depreciation, depletion and amortization) $ 1,182,100 $ 1,207,713 $ 1,091,855 (4) Segment Adjusted EBITDA is defined as net income attributable to ARLP before net interest expense, income taxes, depreciation, depletion and amortization, general and administrative expense, settlement gain, debt extinguishment loss, asset impairment and acquisition gain. Management therefore is able to focus solely on the evaluation of segment operating profitability as it relates to our revenues and operating expenses, which are primarily controlled by our segments. Consolidated Segment Adjusted EBITDA is reconciled to net income as follows: Year Ended December 31, 2019 2018 2017 (in thousands) Consolidated Segment Adjusted EBITDA $ 672,001 $ 715,691 $ 682,028 General and administrative (72,997) (68,298) (61,760) Depreciation, depletion and amortization (309,075) (280,225) (268,981) Settlement gain — 80,000 — Asset impairment (15,190) (40,483) — Interest expense, net (45,496) (40,059) (39,291) Acquisition gain 177,043 — — Debt extinguishment loss — — (8,148) Income tax (expense) benefit 211 (22) (210) Acquisition gain attributable to noncontrolling interest (7,083) — — Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Noncontrolling interest 7,512 866 563 Net income $ 406,926 $ 367,470 $ 304,201 . (5) Capital Expenditures shown exclude the AllDale Acquisition on January 3, 2019 and the Wing Acquisition on August 2, 2019 (Note 3 – Acquisitions).

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2019
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	24. SUBSEQUENT EVENTS Other than those events described in Notes 10 and 16, there were no subsequent events.

SCHEDULE II VALUATION AND QUALI

SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	Dec. 31, 2019
SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS
SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	SCHEDULE II ALLIANCE RESOURCE PARTNERS, L.P. AND SUBSIDIARIES VALUATION AND QUALIFYING ACCOUNTS YEARS ENDED DECEMBER 31, 2019, 2018 AND 2017 Balance At Additions Beginning Charged to Balance At of Year Income Deductions End of Year (in thousands) 2019 Allowance for doubtful accounts $ — $ — $ — $ — 2018 Allowance for doubtful accounts $ — $ — $ — $ — 2017 Allowance for doubtful accounts $ — $ — $ — $ —

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Presentation	Presentation The consolidated financial statements include the accounts and operations of the ARLP Partnership and present our financial position as of December 31, 2019 and 2018, and results of our operations, comprehensive income, cash flows and changes in partners' capital for each of the three years in the period ended December 31, 2019. All of our intercompany transactions and accounts have been eliminated. As a result of the AllDale Acquisition, we now control the underlying oil & gas mineral interests held by AllDale I & II. This control over the oil & gas mineral interests held by AllDale I & II reflects a strategic change in how we manage our business and how resources are allocated by our chief operating decision maker. Due to this strategic change, we realigned our reportable segments in 2019 to include our oil & gas mineral interests within a new Minerals reportable segment. In August 2019, we added the Wing Acquisition to the Minerals reportable segment. As part of our realignment, we have also included the operations of our Mt. Vernon Transfer Terminal, LLC ("Mt. Vernon") and Mid-America Carbonates, LLC ("MAC") subsidiaries in the Illinois Basin reportable segment rather than Other and Corporate to better reflect our Illinois Basin related activities. Prior periods have been recast to include our oil & gas mineral interests in the Minerals segment, and Mt. Vernon and MAC in the Illinois Basin segment. See Note 23 – Segment Information for further discussion of our reportable segments.
Consolidation	Consolidation —
Variable Interest Entity ("VIE")	Variable Interest Entity ("VIE") — To determine a VIE's primary beneficiary, we perform a qualitative assessment to determine which party, if any, has the power to direct activities of the VIE and the obligation to absorb losses and/or receive its benefits. This assessment involves identifying the activities that most significantly impact the VIE's economic performance and determine whether it, or another party, has the power to direct those activities. When evaluating whether we are the primary beneficiary of a VIE, we perform a qualitative analysis that considers the design of the VIE, the nature of our involvement and the variable interests held by other parties. See Note 11 – Variable Interest Entities for further information.
Estimates	Estimates — ● Impairment assessments of investments, property, plant and equipment, and goodwill; ● Asset retirement obligations; ● Pension valuation variables; ● Workers' compensation and pneumoconiosis valuation variables; ● Acquisition related purchase price allocations; and ● Life of mine assumptions; ● Oil & gas reserve quantities and carrying amounts; and ● Determination of oil & gas revenue accruals These significant estimates and assumptions are discussed throughout these notes to the consolidated financial statements.
Fair Value Measurements	Fair Value Measurements — between market participants at the measurement date. Fair value is based upon assumptions that market participants would use when pricing an asset or liability, including assumptions about risk and risks inherent in valuation techniques and inputs to valuations. Fair value measurements assume that the transaction occurs in the principal market for the asset or liability or, in the absence of a principal market, the most advantageous market for the asset or liability (the market for which the reporting entity would be able to maximize the amount received or minimize the amount paid). Valuation techniques used in our fair value measurements are based upon observable and unobservable inputs. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our own market assumptions. We use the following fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value into three broad levels: ● Level 1 – Quoted prices for identical assets and liabilities in active markets that we have the ability to access at the measurement date. ● Level 2 – Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model derived valuations whose inputs are observable or whose significant value drivers are observable. ● Level 3 – Unobservable inputs for the asset or liability including situations where there is little, if any, market activity for the asset or liability. The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall into different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement requires judgment, considering factors specific to the asset or liability. Significant fair value measurements are used in our significant estimates and are discussed throughout these notes.
Cash and Cash Equivalents	Cash and Cash Equivalents —
Cash Management	Cash Management —
Inventories	Inventories —
Business Combinations	Business Combinations —
Goodwill	Goodwill —
Property, Plant and Equipment	Property, Plant and Equipment — current production estimates, are depreciated or depleted using the units-of-production method over a range from 1 to 28 years. Mining equipment and other plant and equipment assets are depreciated principally using the straight-line method over the estimated useful lives of the assets, ranging from 1 to 28 years, limited by the remaining estimated life of each mine. Depreciable lives for buildings, office equipment and improvements range from 1 to 25 years. Gains or losses arising from retirements are included in operating expenses. Depletion of coal mineral rights is provided on the basis of tonnage mined in relation to estimated recoverable tonnage, which equals estimated proven and probable reserves. Therefore, our coal mineral rights are depleted based on only proven and probable reserves. See Oil & Gas Reserve Quantities and Carrying Amounts below for a discussion of our accounting policies for oil & gas properties.
Mine Development Costs	Mine Development Costs —
Long-Lived Asset Impairment	Long-Lived Asset Impairment —
Oil & Gas Reserve Quantities and Carrying Amounts	Oil & Gas Reserve Quantities and Carrying Amounts Mineral interests in oil & gas properties are grouped using a reasonable aggregation of properties with a common geological structural feature or stratigraphic condition, which we may also refer to as a depletable group. Mineral interests in proved oil & gas properties are depleted based on the units-of-production method. Proved reserves are quantities of oil & gas that can be estimated with reasonable certainty to be recoverable in the future from a given date forward, from known reservoirs, under existing economic conditions, operating methods, and government regulations. Proved developed resources are the quantities expected to be recovered through our operators' existing wells with existing equipment, infrastructure and operating methods. We evaluate impairment of our mineral interests in proved properties whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. This evaluation is performed on a depletable group basis. We compare the undiscounted projected future cash flows expected in connection with a depletable group to its unamortized carrying amount to determine recoverability. When the carrying amount of a depletable group exceeds its estimated undiscounted future cash flows, the carrying amount is written down to its fair value, which is measured as the present value of the projected future cash flows of such properties. The factors used to determine fair value include estimates of proved reserves, future commodity prices, timing of future production, future expenditures, and a risk-adjusted discount rate. Our mineral interests in unproved properties are also assessed for impairment periodically on a depletable group basis when facts and circumstances indicate that the carrying value may not be recoverable. Impairment of individual unproved properties whose acquisition costs are relatively significant are assessed on a property-by-property basis, and an impairment loss is recognized to the extent the carrying value exceeds the estimated recoverable value for the property. Impairment of unproved properties whose acquisition costs are not individually significant are assessed on a group basis. Any amount of loss to be recognized and the amount of a valuation allowance needed to provide for impairment of those properties is determined by amortizing those properties in the aggregate on the basis of historical experience and other relevant information, such as the relative proportion of such properties on which proved reserves have been found in the past. The carrying value of unproved properties, including unleased mineral rights, are determined based on management's assessment of fair value using factors similar to those previously noted for proved properties, as well as geographic and geologic data. Upon the sale of a complete depletable group, the book value thereof, less proceeds or salvage value, are charged to income. Upon the sale or retirement of an aggregation of interests which make up less than a complete depletable group, the proceeds are credited to accumulated depreciation, depletion and amortization, unless doing so would significantly alter the depreciation, depletion and amortization rate of the depletable group, in which case a gain or loss would be recorded.
Intangibles	Intangibles — Prepaid expenses and other assets Other long-term assets December 31, 2019 December 31, 2018 Accumulated Intangibles, Accumulated Intangibles, Original Cost Amortization Net Original Cost Amortization Net (in thousands) Non-compete agreements $ 9,803 $ (9,440) $ 363 $ 9,697 $ (8,385) $ 1,312 Customer contracts and other 32,371 (24,258) 8,113 23,000 (16,293) 6,707 Mining permits 1,500 (307) 1,193 1,500 (241) 1,259 Total $ 43,674 $ (34,005) $ 9,669 $ 34,197 $ (24,919) $ 9,278 Amortization expense attributable to intangible assets is estimated as follows: Year Ended December 31, (in thousands) 2020 $ 4,495 2021 2,952 2022 647 2023 647 2024 66 Thereafter 862
Investments	Investments Our investments and ownership interests in entities in which we do not have a controlling financial interest are accounted for under the equity method of accounting if we have the ability to exercise significant influence over the entity. Investments accounted for under the equity method are initially recorded at cost, and the difference between the basis of our investment and the underlying equity in the net assets of the joint venture at the investment date, if any, is amortized over the lives of the related assets that gave rise to the difference. As of December 31, 2019, we held an equity method investment in AllDale III through our subsidiary, Alliance Minerals, LLC ("Alliance Minerals"). Prior to the AllDale Acquisition, our equity method investments also included AllDale I & II, both held through Cavalier Minerals. AllDale III and AllDale I & II are collectively referred to as the "AllDale Partnerships." See Note 12 – Investments for further discussion of our equity method investment in AllDale III and Note 3 – Acquisitions for discussion of the AllDale Acquisition. We review our investments for impairment whenever events or changes in circumstances indicate a loss in the value of the investment may be other-than-temporary.
Advance Royalties, net	Advance Royalties — Advance royalties December 31, 2019 2018 (in thousands) Advance royalties, affiliates (see Note 20 – Related-Party Transactions) $ 41,216 $ 32,645 Advance royalties, third-parties 12,685 11,552 Total advance royalties $ 53,901 $ 44,197
Asset Retirement Obligations	Asset Retirement Obligations —
Pension Benefits	Pension Benefits — The discount rate is determined for our pension benefit plan based on an approach specific to our plan. The year end discount rate is determined considering a yield curve comprised of high-quality corporate bonds and the timing of the expected benefit cash flows. The expected long-term rate of return on plan assets is determined based on broad equity and bond indices, the investment goals and objectives, the target investment allocation and on the average annual total return for each asset class. Unrecognized actuarial gains and losses and unrecognized prior service costs and credits are deferred and recorded in accumulated other comprehensive loss until amortized as a component of net periodic benefit cost. Unrecognized actuarial gains and losses in excess of 10% of the greater of the benefit obligation or the market-related value of plan assets are amortized over the participants' average remaining future years of service.
Workers' Compensation and Pneumoconiosis (Black Lung) Benefits	Workers ' Compensation and Pneumoconiosis (Black Lung) Benefits — We provide income replacement and medical treatment for work-related traumatic injury claims as required by applicable state laws. Workers' compensation laws also compensate survivors of workers who suffer employment related deaths. Our liability for traumatic injury claims is the estimated present value of current workers' compensation benefits, based on our actuarial estimates. Our actuarial calculations are based on a blend of actuarial projection methods and numerous assumptions including claim development patterns, mortality, medical costs and interest rates. Our pneumoconiosis benefits liability is calculated using the service cost method based on the actuarial present value of the estimated pneumoconiosis obligation. Our actuarial calculations are based on numerous assumptions including claim development patterns, medical costs and mortality. Actuarial gains or losses are amortized over the remaining service period of active miners. See Note 19 – Accrued Workers' Compensation and Pneumoconiosis Benefits for more information on Workers' Compensation and Pneumoconiosis Benefits.
Revenue Recognition	Coal Revenue Recognition — The estimated transaction price from each of our contracts is based on the total amount of consideration we expect to be entitled to under the contract. Included in the transaction price for certain coal supply contracts is the impact of variable consideration, including quality price adjustments, handling services, government imposition claims, per ton price fluctuations based on certain coal sales price indices and anticipated payments in lieu of shipments. We have constrained the expected value of variable consideration in our estimation of transaction price and only included this consideration to the extent that it is probable that a significant revenue reversal will not occur. The estimated transaction price for each contract is allocated to our performance obligations based on relative standalone selling prices determined at contract inception. Variable consideration is allocated to a specific part of the contract in many instances, such as if the variable consideration is based on production activities for coal delivered during a certain period or the outcome of a customer's ability to accept coal shipments over a certain period. Contract assets are recorded as trade receivables and reported separately in our consolidated balance sheet from other contract assets as title passes to the customer and our right to consideration becomes unconditional. Payments for coal shipments are typically due within two four weeks Oil & Gas Revenue Recognition — We also periodically earn revenue from lease bonuses. We generate lease bonus revenue by leasing our mineral interests to exploration and production companies. A lease agreement represents our contract with an operator, which is generally an exploration and production company. The contract will a) generally transfer the rights to any oil or gas discovered, b) grant us a right to a specified royalty interest from the operator, and c) require the operator to commence drilling and complete operations within a specified time period. Control of the minerals transfers to the operator when the lease agreement is executed. At the time we execute the lease agreement, we expect to receive the lease bonus payment within a reasonable time, though in no case more than one year, such that we do not adjust the expected amount of consideration for the effects of any significant financing component. As a non-operator, we have limited visibility into the timing of when new wells start producing, in addition, production statements may not be received for 30 to 90 days or more after the date production is delivered. As a result, we are required to estimate the amount of production delivered to the purchaser and the price that will be received for the sale of the product. The expected sales volumes and prices from our properties are estimated and recorded within the Trade receivables
Common Unit-Based Compensation	Common Unit-Based Compensation — We utilize the Supplemental Executive Retirement Plan ("SERP") to provide deferred compensation benefits for certain officers and key employees. All allocations made to participants under the SERP are made in the form of "phantom" ARLP units and SERP distributions will be settled in the form of ARLP common units. The SERP is administered by the Compensation Committee. Our directors participate in the MGP Amended and Restated Deferred Compensation Plan for Directors ("Directors' Deferred Compensation Plan"). Pursuant to the Directors' Deferred Compensation Plan, for amounts deferred either automatically or at the election of the director, a notional account is established and credited with notional common units of ARLP, described in the Directors' Deferred Compensation Plan as "phantom" units. Distributions from the Directors' Deferred Compensation Plan will be settled in the form of ARLP common units. For both the SERP and Directors' Deferred Compensation Plan, when quarterly cash distributions are made with respect to ARLP common units, an amount equal to such quarterly distribution is credited to each participant's notional account as additional phantom units. All grants of phantom units under the SERP and Directors' Deferred Compensation Plan vest immediately. The fair value of restricted common unit grants under the LTIP, SERP and the Directors' Deferred Compensation Plan are determined on the grant date of the award and recognized as compensation expense on a pro rata basis for LTIP and SERP awards, as appropriate, over the requisite service period. Compensation expense is fully recognized on the grant date for quarterly distributions credited to SERP accounts and Directors' Deferred Compensation Plan awards. The corresponding liability is classified as equity and included in limited partners' capital in the consolidated financial statements (See Note 16 – Compensation Plans).
Income Taxes	Income Taxes
New Accounting Standards	New Accounting Standards Issued and Adopted — January 1, 2019 As part of our transition there are a number of practical expedients available in the new standard. We elected a package of practical expedients that, among other things, allows us to not reassess the lease classification of expired or existing leases. In addition to the package of practical expedients, we also elected to use a practical expedient allowing us to use hindsight in determining the lease term for existing leases. New Accounting Standards Issued and Not Yet Adopted — Financial Instruments–Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	Dec. 31, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Summary of intangible assets	December 31, 2019 December 31, 2018 Accumulated Intangibles, Accumulated Intangibles, Original Cost Amortization Net Original Cost Amortization Net (in thousands) Non-compete agreements $ 9,803 $ (9,440) $ 363 $ 9,697 $ (8,385) $ 1,312 Customer contracts and other 32,371 (24,258) 8,113 23,000 (16,293) 6,707 Mining permits 1,500 (307) 1,193 1,500 (241) 1,259 Total $ 43,674 $ (34,005) $ 9,669 $ 34,197 $ (24,919) $ 9,278
Schedule of estimated amortization expense attributable to intangible assets	Year Ended December 31, (in thousands) 2020 $ 4,495 2021 2,952 2022 647 2023 647 2024 66 Thereafter 862
Summary of advance royalties	December 31, 2019 2018 (in thousands) Advance royalties, affiliates (see Note 20 – Related-Party Transactions) $ 41,216 $ 32,645 Advance royalties, third-parties 12,685 11,552 Total advance royalties $ 53,901 $ 44,197

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
ACQUISITIONS (Tables)	Dec. 31, 2019
AllDale I and II
ACQUISITIONS
Schedule of total fair value of consideration transferred	As of January 3, 2019 (in thousands) Cash $ 176,205 Previously held investments 307,322 Total $ 483,527
Summary of fair value allocation of assets acquired and liabilities assumed	Preliminary Adjustments Final (in thousands) Cash and cash equivalents $ 900 $ 900 Mineral interests in proved properties 159,617 24,415 184,032 Mineral interests in unproved properties 314,084 (22,894) 291,190 Receivables 10,602 (1,276) 9,326 Accounts payable (1,921) (1,921) Net assets acquired $ 483,282 $ 483,527
Schedule of revenue and earnings since acquisition date and pro forma condensed consolidated income statement	Year Ended December 31, 2019 (in thousands) Revenue $ 48,411 Net income 18,543 Year Ended December 31, 2018 (in thousands) Total revenues As reported $ 2,002,857 Pro forma 2,042,545 Net income As reported $ 367,470 Pro forma 358,741
Wing
ACQUISITIONS
Summary of fair value allocation of assets acquired and liabilities assumed	As Previously Reported Adjustments Adjusted (in thousands) Mineral interests in proved properties $ 55,619 2,465 $ 58,084 Mineral interests in unproved properties 87,441 (2,465) 84,976 Receivables 1,867 1,867 Net assets acquired $ 144,927 $ 144,927
Schedule of revenue and earnings since acquisition date and pro forma condensed consolidated income statement	Year Ended December 31, 2019 (in thousands) Revenue $ 4,625 Net income 1,291 The following represents our actual and pro forma consolidated revenues and net income for the years ended December 31, 2019 and 2018. Pro forma revenues and net income assumes the mineral interests acquired in the Wing Acquisition had been included in our consolidated results since January 1, 2018. These pro forma amounts have been calculated after applying our accounting policies. Year Ended December 31, 2019 2018 (in thousands) Total revenues As reported $ 1,961,720 $ 2,002,857 Pro forma 1,966,291 2,008,559 Net income As reported $ 406,926 $ 367,470 Pro forma 411,217 372,810

INVENTORIES (Tables)

INVENTORIES (Tables)	12 Months Ended
INVENTORIES (Tables)	Dec. 31, 2019
INVENTORIES
Schedule of inventories	December 31, 2019 2018 (in thousands) Coal $ 63,645 $ 20,929 Supplies (net of reserve for obsolescence of $5,555 and $5,453, respectively) 37,660 38,277 Total inventories, net $ 101,305 $ 59,206

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
PROPERTY, PLANT AND EQUIPMENT (Tables)	Dec. 31, 2019
PROPERTY, PLANT AND EQUIPMENT
Schedule of property, plant and equipment	December 31, 2019 2018 (in thousands) Mining equipment and processing facilities $ 1,937,642 $ 1,851,479 Land and coal mineral rights 453,237 445,411 Oil & gas mineral interests (1) 618,282 — Buildings, office equipment and improvements 304,111 287,053 Construction and mine development in progress 86,876 71,190 Mine development costs 283,860 270,675 Property, plant and equipment, at cost 3,684,008 2,925,808 Less accumulated depreciation, depletion and amortization (1,675,022) (1,513,450) Total property, plant and equipment, net $ 2,008,986 $ 1,412,358 (1) Oil & gas mineral interests acquired in the AllDale and Wing Acquisitions. See Note 3 – Acquisitions for more information.

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
LONG-TERM DEBT (Tables)	Dec. 31, 2019
LONG-TERM DEBT
Schedule of long-term debt	Unamortized Discount and Principal Debt Issuance Costs December 31, December 31, 2019 2018 2019 2018 (in thousands) Revolving credit facility $ 255,000 $ 175,000 $ (3,050) $ (5,203) Senior notes 400,000 400,000 (4,879) (5,793) Securitization facility 73,800 92,000 — — May 2019 equipment financing 8,199 — — — November 2019 equipment financing 52,281 — — — 789,280 667,000 (7,929) (10,996) Less current maturities (13,157) (92,000) — — Total long-term debt $ 776,123 $ 575,000 $ (7,929) $ (10,996)
Schedule of aggregate maturities of long-term debt	Year Ended December 31, (in thousands) 2020 $ 13,157 2021 342,648 2022 12,403 2023 21,072 2024 — Thereafter 400,000 $ 789,280

LEASES (Tables)

LEASES (Tables)	12 Months Ended
LEASES (Tables)	Dec. 31, 2019
LEASES
Schedule of lease cost and other information	The components of lease expense were as follows: December 31, 2019 (in thousands) Finance lease cost: Amortization of right-of-use assets $ 14,608 Interest on lease liabilities 2,085 Operating lease cost 9,169 Short-term lease cost 464 Variable lease cost 1,360 Total lease cost $ 27,686 Supplemental cash flow information related to leases was as follows: December 31, 2019 (in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 9,124 Operating cash flows for finance leases $ 891 Financing cash flows for finance leases $ 46,725 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ 25,593 Supplemental balance sheet information related to leases was as follows: December 31, 2019 2018 (in thousands) Finance leases: Property and equipment finance lease assets, gross $ 30,610 $ 141,019 Accumulated depreciation (20,564) (74,576) Property and equipment finance lease assets, net $ 10,046 $ 66,443 December 31, 2019 Weighted average remaining lease term Operating leases 13.1 years Finance leases 1.6 years Weighted average discount rate Operating leases 6.0 % Finance leases 6.0 %
Schedule of maturities of operating lease liabilities	Operating leases Finance leases (in thousands) 2020 $ 3,832 $ 8,747 2021 2,280 912 2022 2,217 912 2023 2,040 139 2024 1,820 139 Thereafter 13,539 419 Total lease payments 25,728 11,268 Less imputed interest (8,161) (676) Total $ 17,567 $ 10,592
Schedule of maturities of finance lease liabilities	Operating leases Finance leases (in thousands) 2020 $ 3,832 $ 8,747 2021 2,280 912 2022 2,217 912 2023 2,040 139 2024 1,820 139 Thereafter 13,539 419 Total lease payments 25,728 11,268 Less imputed interest (8,161) (676) Total $ 17,567 $ 10,592

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
FAIR VALUE MEASUREMENTS (Tables)	Dec. 31, 2019
FAIR VALUE MEASUREMENTS
Summary of fair value measurements within the hierarchy	December 31, 2019 December 31, 2018 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 (in thousands) Long-term debt $ — $ 736,206 $ — $ — $ 669,864 $ — Total $ — $ 736,206 $ — $ — $ 669,864 $ —

PARTNERS' CAPITAL (Tables)

PARTNERS' CAPITAL (Tables)	12 Months Ended
PARTNERS' CAPITAL (Tables)	Dec. 31, 2019
PARTNERS' CAPITAL
Summary of quarterly per unit distribution paid	Year Ended December 31, 2019 2018 2017 First Quarter $ 0.5300 $ 0.5100 $ 0.4375 Second Quarter $ 0.5350 $ 0.5150 $ 0.4375 Third Quarter $ 0.5400 $ 0.5200 $ 0.5000 Fourth Quarter $ 0.5400 $ 0.5250 $ 0.5050

VARIABLE INTEREST ENTITIES (Tab

VARIABLE INTEREST ENTITIES (Tables)	12 Months Ended
VARIABLE INTEREST ENTITIES (Tables)	Dec. 31, 2019
VARIABLE INTEREST ENTITIES
Schedule of distributions	Alliance Bluegrass Minerals Minerals (in thousands) Contributions $ 143,112 $ 5,963 Distributions 71,916 2,996

INVESTMENTS (Tables)

INVESTMENTS (Tables)	12 Months Ended
INVESTMENTS (Tables)	Dec. 31, 2019
INVESTMENTS
Schedule of changes in equity method investment	Year Ended December 31, 2019 2018 2017 (in thousands) Beginning balance $ 28,974 $ 14,182 $ — Contributions — 15,600 14,400 Equity method investment income (loss) 2,203 547 (218) Distributions received (2,648) (1,355) — Ending balance $ 28,529 $ 28,974 $ 14,182

REVENUE FROM CONTRACTS WITH C_2

REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)	12 Months Ended
REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)	Dec. 31, 2019
REVENUE FROM CONTRACTS WITH CUSTOMERS
Schedule of disaggregation of revenues by type	Illinois Other and Basin Appalachia Minerals Corporate Elimination Consolidated (in thousands) Year Ended December 31, 2019 Coal sales $ 1,128,588 $ 628,406 $ — $ 22,138 $ (16,690) $ 1,762,442 Oil & gas royalties — — 51,735 — — 51,735 Transportation revenues 94,686 4,817 — — — 99,503 Other revenues 13,034 11,166 1,301 34,712 (12,173) 48,040 Total revenues $ 1,236,308 $ 644,389 $ 53,036 $ 56,850 $ (28,863) $ 1,961,720 Year Ended December 31, 2018 Coal sales $ 1,197,143 $ 635,530 $ — $ 43,393 $ (31,258) $ 1,844,808 Transportation revenues 106,947 5,435 — 3 — 112,385 Other revenues 16,999 3,000 — 38,096 (12,431) 45,664 Total revenues $ 1,321,089 $ 643,965 $ — $ 81,492 $ (43,689) $ 2,002,857 Year Ended December 31, 2017 Coal sales $ 1,078,255 $ 616,305 $ — $ 74,973 $ (58,419) $ 1,711,114 Transportation revenues 35,585 6,115 — — — 41,700 Other revenues 12,024 3,621 — 39,776 (12,015) 43,406 Total revenues $ 1,125,864 $ 626,041 $ — $ 114,749 $ (70,434) $ 1,796,220
Schedule of current coal supply contracts allocated to performance obligations that are unsatisfied or partially unsatisfied	2023 and 2020 2021 2022 Thereafter Total (in thousands) Illinois Basin coal revenues $ 849,040 $ 437,808 $ 34,414 $ 8,470 $ 1,329,732 Appalachia coal revenues 426,162 97,729 54,132 — 578,023 Total coal revenues (1) $ 1,275,202 $ 535,537 $ 88,546 $ 8,470 $ 1,907,755 (1) Coal revenues generally consists of consolidated revenues excluding our Minerals segment.

EARNINGS PER LIMITED PARTNER _2

EARNINGS PER LIMITED PARTNER UNIT (Tables)	12 Months Ended
EARNINGS PER LIMITED PARTNER UNIT (Tables)	Dec. 31, 2019
EARNINGS PER LIMITED PARTNER UNIT
Reconciliation of net income and EPU calculations	Year Ended December 31, 2019 2018 2017 (in thousands, except per unit data) Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Adjustments: MGP's priority distributions (1) — — (19,216) General partners' equity ownership (1) — (1,560) (3,688) General partner's special allocation of certain general and administrative expenses (2) — — 1,000 Limited partners' interest in net income attributable to ARLP 399,414 365,044 281,734 Less: Distributions to participating securities (4,254) (5,114) (4,339) Undistributed earnings attributable to participating securities (2,237) (1,641) (1,026) Net income attributable to ARLP available to limited partners $ 392,923 $ 358,289 $ 276,369 Weighted-average limited partner units outstanding – basic and diluted 128,117 130,758 98,708 Earnings per limited partner unit - basic and diluted (3) $ 3.07 $ 2.74 $ 2.80 (1) Amounts for 2019 and 2018 reflect the impact of the Simplification Transactions which ended net income allocations and quarterly cash distributions to MGP after May 31, 2018. Amounts for 2017 reflect the impact of the Exchange Transaction ending distributions that would have been paid for the IDRs and a 0.99% general partner interest in ARLP, both of which were held by MGP prior to the 2017 Exchange Transaction. For the time period between the Exchange Transaction and the Simplification Transactions, MGP maintained a 1.0001% general partner interest in the Intermediate Partnership and a 0.001% managing member interest in Alliance Coal and thus received quarterly distributions and income and loss allocations during this time period. The SGP had a nominal general partner interest prior to the Exchange Transaction. (2) MGP made a capital contribution of $1.0 million during 2017 to Alliance Coal for the purpose of funding certain general and administrative expenses. As provided under our partnership agreement, we made a special allocation to MGP of certain general and administrative expenses equal to its contribution. Net income attributable to ARLP allocated to the limited partners was not burdened by this expense. See Note 10 – Partners' Capital for more information regarding this contribution. (3) Diluted EPU gives effect to all potentially dilutive common units outstanding during the period using the treasury stock method. Diluted EPU excludes all potentially dilutive units calculated under the treasury stock method if their effect is anti-dilutive. For the years ended December 31, 2019, 2018 and 2017, the combined total of LTIP, SERP and Directors' Deferred Compensation Plan units of 1,284,013 , 1,658,908 and 1,466,404 , respectively, were considered anti-dilutive under the treasury stock method.
Pro Forma
EARNINGS PER LIMITED PARTNER UNIT
Reconciliation of net income and EPU calculations	Year Ended December 31, 2019 2018 2017 (in thousands, except per unit data) Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Pro forma adjustments (1) — (1,265) (1,943) Pro forma net income of ARLP 399,414 365,339 301,695 Less: Distributions to participating securities (4,254) (5,114) (4,339) Undistributed earnings attributable to participating securities (2,237) (1,627) (680) Net income attributable to ARLP available to limited partners (2) $ 392,923 $ 358,598 $ 296,676 Weighted-average limited partner units outstanding – basic and diluted (2) 128,117 131,310 132,024 Pro forma earnings per limited partner unit - basic and diluted (3) $ 3.07 $ 2.73 $ 2.25 (1) Pro forma adjustments to net income attributable to ARLP primarily represent the elimination of administrative service revenues from AHGP and the inclusion of general and administrative expenses incurred at AHGP. (2) Net income attributable to ARLP available to limited partners reflects net income allocations made for all periods presented based on the ownership structure subsequent to the Simplification Transactions. Accordingly, no general partner income allocations are presented above. Pro forma amounts above also reflect weighted average units outstanding as if the issuance of 56,128,141 ARLP common units in the Exchange Transaction and 1,322,388 ARLP common units in the Simplification Transactions applied to all periods presented. (3) Diluted EPU gives effect to all potentially dilutive common units outstanding during the period using the treasury stock method. Diluted EPU excludes all potentially dilutive units calculated under the treasury stock method if their effect is anti-dilutive. For the years ended December 31, 2019, 2018 and 2017, the combined total of LTIP, SERP and Directors' Deferred Compensation Plan units of 1,284,013 , 1,658,908 and 1,466,404 , respectively, were considered anti-dilutive under the treasury stock method. .

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables) - Defined benefit pension plan	12 Months Ended
	Dec. 31, 2019
Employee Benefit Plans
Summary of benefit plans for employees	December 31, 2019 2018 (dollars in thousands) Change in benefit obligations: Benefit obligations at beginning of year $ 118,958 $ 127,298 Interest cost 4,864 4,462 Actuarial loss (gain) 17,084 (8,562) Benefits paid (4,481) (4,240) Benefit obligations at end of year 136,425 118,958 Change in plan assets: Fair value of plan assets at beginning of year 75,823 81,981 Employer contribution 5,559 4,187 Actual return on plan assets 14,666 (6,105) Benefits paid (4,481) (4,240) Fair value of plan assets at end of year 91,567 75,823 Funded status at the end of year $ (44,858) $ (43,135) Amounts recognized in balance sheet: Non-current liability $ (44,858) $ (43,135) Amounts recognized in accumulated other comprehensive income consists of: Prior service cost $ (940) $ (1,126) Net actuarial loss (45,125) (41,697) $ (46,065) $ (42,823) Weighted-average assumption to determine benefit obligations as of December 31, Discount rate 3.15% 4.17% Weighted-average assumptions used to determine net periodic benefit cost for the year ended December 31, Discount rate 4.17% 3.54% Expected return on plan assets 6.50% 7.00%
Schedule of long-term rate of return assumptions	Asset allocation As of December 31, 2019 assumption Equity securities 62% Fixed income securities 33% Real estate 5% 100%
Components of net periodic benefit cost	Year Ended December 31, 2019 2018 2017 (in thousands) Components of net periodic benefit cost: Interest cost $ 4,864 $ 4,462 $ 4,587 Expected return on plan assets (4,932) (5,784) (4,978) Amortization of prior service cost 186 186 186 Amortization of net loss 3,922 3,608 3,054 Net periodic benefit cost (1) $ 4,040 $ 2,472 $ 2,849 (1) Nonservice components of net periodic benefit cost are included in the Other income (expense) line item within our consolidated statements of income (see Note 2 – Summary of Significant Accounting Policies ).
Schedule of other changes in plan assets and benefit obligation recognized in accumulated other comprehensive income	Year Ended December 31, 2019 2018 (in thousands) Other changes in plan assets and benefit obligation recognized in accumulated other comprehensive loss: Net actuarial loss $ (7,350) $ (3,326) Reversal of amortization item: Prior service cost 186 186 Net actuarial loss 3,922 3,608 Total recognized in accumulated other comprehensive loss (3,242) 468 Net periodic benefit cost (4,040) (2,472) Total recognized in net periodic benefit cost and accumulated other comprehensive loss $ (7,282) $ (2,004)
Schedule of estimated future benefit payments	Year Ended December 31, (in thousands) 2020 $ 5,288 2021 5,677 2022 6,045 2023 6,342 2024 6,507 2025-2029 34,755 $ 64,614
Schedule of asset allocation guidelines, actual asset allocations and fair value of Pension Plan assets	Percentage of Total Portfolio Minimum Target Maximum Equity securities 45% 62% 80% Fixed income securities 10% 33% 55% Real estate 0% 5% 10% December 31, 2019 2018 (in thousands) Cash and cash equivalents (a) $ 2,958 $ 5,277 Commingled investment funds measured at net asset value (b): Equities - Global 10,028 — Equities - United States large-cap 19,220 21,862 Equities - United States small-cap 7,592 5,259 Equities - International developed markets 10,528 10,593 Equities - International emerging markets 8,410 4,808 Fixed income - Investment grade 26,186 15,777 Fixed income - High yield — 4,508 Real estate 4,355 5,034 Other 2,290 2,705 Total $ 91,567 $ 75,823 (a) Cash and cash equivalents represents a Level 1 fair value measurement. See Note 2 – Summary of Significant Accounting Policies – Fair Value Measurements for more information regarding the definitions of fair value hierarchy levels. (b) Investments measured at fair value using the net asset value per share (or its equivalent) have not been classified within the fair value hierarchy. The fair values of all commingled investment funds are determined based on the net asset values per unit of each of the funds. The net asset values per unit represent the aggregate value of the fund's assets at fair value less liabilities, divided by the number of units outstanding.

COMPENSATION PLANS (Tables)

COMPENSATION PLANS (Tables)	12 Months Ended
COMPENSATION PLANS (Tables)	Dec. 31, 2019
ARLP LTIP
Compensation Plans
Summary of activity in share-based plans	Number of units Weighted average grant date fair value per unit Intrinsic value (in thousands) Non-vested grants at January 1, 2017 1,604,748 $ 23.19 $ 36,027 Granted 475,310 23.17 Vested (1) (350,516) 40.73 Forfeited (35,516) 20.01 Non-vested grants at December 31, 2017 1,694,026 19.62 33,372 Granted 511,305 20.40 Vested (1) (331,502) 34.61 Forfeited (45,749) 17.40 Non-vested grants at December 31, 2018 1,828,080 17.18 31,699 Granted 682,155 18.63 Vested (1) (885,381) 12.38 Forfeited (21,476) 20.84 Non-vested grants at December 31, 2019 1,603,378 20.39 17,349 (1) During the years ended December 31, 2019, 2018 and 2017, we issued 596,650 , 191,858 and 222,011 , respectively, unrestricted common units to the LTIP participants. The remaining vested units were settled in cash primarily to satisfy tax withholding obligations of the LTIP participants.
SERP and Directors' Compensation Plans
Compensation Plans
Summary of activity in share-based plans	Number of units Weighted average grant date fair value per unit Intrinsic value (in thousands) Phantom units outstanding as of January 1, 2017 494,018 $ 29.77 $ 11,091 Granted 67,766 20.38 Phantom units outstanding as of December 31, 2017 561,784 28.64 11,067 Granted 84,417 18.78 Issued (1) (10,364) 27.92 Phantom units outstanding as of December 31, 2018 635,837 27.34 11,025 Granted 111,012 14.50 Issued (1) (115,484) 25.20 Phantom units outstanding as of December 31, 2019 631,365 25.48 6,831 (1) During the years ended December 31, 2019 and 2018, we issued ARLP common units of 115,484 and 7,181 , respectively, to participants under the SERP and Directors' Deferred Compensation Plan . Units issued in 2018 were net of units settled in cash to satisfy tax withholding obligations.

SUPPLEMENTAL CASH FLOW INFORM_2

SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	12 Months Ended
SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	Dec. 31, 2019
SUPPLEMENTAL CASH FLOW INFORMATION
Schedule of supplemental cash flow information	Year Ended December 31, 2019 2018 2017 (in thousands) Cash Paid For: Interest $ 43,093 $ 38,450 $ 31,692 Income taxes $ — $ 34 $ 210 Non-Cash Activity: Accounts payable for purchase of property, plant and equipment $ 14,504 $ 14,585 $ 15,636 Assets acquired by finance lease $ — $ 835 $ — Right-of-use assets acquired by operating lease $ 25,593 — — Market value of common units issued under deferred compensation plans before tax withholding requirements $ 17,415 $ 6,142 $ 8,149 Acquisition of businesses: Fair value of assets assumed $ 629,475 $ — $ — Previously held equity-method investments (1) (307,322) — — Cash paid, net of cash acquired (320,232) — — Fair value of liabilities assumed $ 1,921 $ — $ — (1) Inclusive of gain of $177.0 million as discussed in Note 3 – Acquisitions.

ASSET RETIREMENT OBLIGATIONS (T

ASSET RETIREMENT OBLIGATIONS (Tables)	12 Months Ended
ASSET RETIREMENT OBLIGATIONS (Tables)	Dec. 31, 2019
ASSET RETIREMENT OBLIGATIONS
Schedule of activity affecting the asset retirement and mine closing liability	Year Ended December 31, 2019 2018 (in thousands) Beginning balance $ 137,114 $ 130,600 Accretion expense 4,087 3,926 Payments (2,948) (2,392) Allocation of liability associated with acquisitions, mine development and change in assumptions (739) 4,980 Ending balance $ 137,514 $ 137,114
Schedule of estimated payments of asset retirement obligations	Year Ended December 31, (in thousands) 2020 $ 4,496 2021 2,576 2022 2,794 2023 2,027 2024 2,986 Thereafter 225,584 Aggregate undiscounted asset retirement obligations 240,463 Effect of discounting (102,949) Total asset retirement obligations 137,514 Less: current portion (4,496) Asset retirement obligations $ 133,018

ACCRUED WORKERS' COMPENSATION_2

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS (Tables)	12 Months Ended
	Dec. 31, 2019
Accrued Workers Compensation And Pneumoconiosis Benefits
Reconciliation of changes in workers' compensation liability	December 31, 2019 2018 (in thousands) Beginning balance $ 49,539 $ 54,439 Accruals increase 7,162 7,654 Payments (11,320) (10,837) Interest accretion 1,606 1,454 Valuation loss (gain) 6,397 (3,171) Ending balance $ 53,384 $ 49,539
Reconciliation of changes in pneumoconiosis benefit obligation	December 31, 2019 2018 (in thousands) Benefit obligations at beginning of year $ 72,095 $ 74,859 Service cost 2,593 2,525 Interest cost 3,044 2,542 Actuarial (gain) loss 23,298 (4,599) Benefits and expenses paid (3,347) (3,232) Benefit obligations at end of year $ 97,683 $ 72,095
Components of pneumoconiosis and workers' compensation expense	Year Ended December 31, 2019 2018 2017 (in thousands) Black lung benefits: Service cost $ 2,593 $ 2,525 $ 2,255 Interest cost (1) 3,044 2,542 2,555 Net amortization (1) (4,582) 2 (2,092) Total pneumoconiosis expense 1,055 5,069 2,718 Workers' compensation expense 17,541 11,270 12,215 Net periodic benefit cost $ 18,596 $ 16,339 $ 14,933 ________________________________________ (1) Interest cost and net amortization is included in the Other income (expense) line item within our consolidated statements of income ( see Note 2 – Summary of Significant Accounting Policies).
Pneumoconiosis benefits
Accrued Workers Compensation And Pneumoconiosis Benefits
Reconciliation of changes in the pneumoconiosis benefit obligation recognized in AOCI	Year Ended December 31, 2019 2018 2017 (in thousands) Net actuarial gain (loss) $ (23,298) $ 4,599 $ (7,938) Reversal of amortization item: Net actuarial (gain) loss (4,582) 2 (2,092) Total recognized in accumulated other comprehensive loss $ (27,880) $ 4,601 $ (10,030)
Schedule of amount recognized in accumulated other comprehensive income	Year Ended December 31, 2019 2018 2017 (in thousands) Amount recognized in accumulated other comprehensive loss consists of: Net actuarial loss $ 31,927 $ 4,047 $ 8,648
Summary of information about amounts recognized in the consolidated balance sheets	December 31, 2019 2018 (in thousands) Workers’ compensation claims $ 53,384 $ 49,539 Pneumoconiosis benefit claims 97,683 72,095 Total obligations 151,067 121,634 Less current portion (11,175) (11,137) Non-current obligations $ 139,892 $ 110,497

RELATED-PARTY TRANSACTIONS (Tab

RELATED-PARTY TRANSACTIONS (Tables)	12 Months Ended
RELATED-PARTY TRANSACTIONS (Tables)	Dec. 31, 2019
RELATED-PARTY TRANSACTIONS
Summary of advanced royalties outstanding	WKY CoalPlay Towhead Webster Henderson WKY SGP/Craft Foundations Coal Coal Coal CoalPlay Henderson Henderson Tunnel & Union Webster Henderson & Union Ridge Counties, KY County, KY County, KY Counties, KY Total Acquired Acquired Acquired Acquired Acquired 2005 December 2014 December 2014 December 2014 February 2015 (in thousands) As of January 1, 2017 — 7,195 3,319 5,044 4,262 19,820 Payments 6,000 3,598 2,568 2,522 2,131 16,819 Recoupment (3,000) (109) (531) — (6) (3,646) As of December 31, 2017 3,000 10,684 5,356 7,566 6,387 32,993 Payments — 3,597 2,570 2,520 2,131 10,818 Recoupment (3,000) (204) (31) — (36) (3,271) Unrecoupable — — (7,895) — — (7,895) As of December 31, 2018 — 14,077 — 10,086 8,482 32,645 Payments 4,500 3,597 2,568 2,521 2,131 15,317 Recoupment (3,000) (1,071) — — (107) (4,178) Unrecoupable — — (2,568) — — (2,568) As of December 31, 2019 1,500 16,603 — 12,607 10,506 41,216

CONCENTRATION OF CREDIT RISK _2

CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS (Tables)	12 Months Ended
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS (Tables)	Dec. 31, 2019
CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS
Schedule of total revenues from major customers	Year Ended December 31, Segment 2019 2018 2017 (in thousands) Customer A Illinois Basin $ 228,500 $ 219,115 $ — Customer B Appalachia 213,319 — —

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
SEGMENT INFORMATION (Tables)	Dec. 31, 2019
SEGMENT INFORMATION
Schedule of reportable segment results	Illinois Other and Elimination Basin Appalachia Minerals Corporate (1) Consolidated (in thousands) Year Ended December 31, 2019 Revenues - Outside $ 1,219,618 $ 644,389 $ 53,036 $ 44,677 $ — $ 1,961,720 Revenues - Intercompany 16,690 — — 12,173 (28,863) — Total revenues (2) 1,236,308 644,389 53,036 56,850 (28,863) 1,961,720 Segment Adjusted EBITDA Expense (3) 756,423 423,623 7,811 36,845 (19,806) 1,204,896 Segment Adjusted EBITDA (4) 385,200 215,950 46,997 32,911 (9,057) 672,001 Total assets 1,373,516 500,027 643,213 541,261 (471,323) 2,586,694 Capital expenditures (5) 189,270 111,739 — 4,849 — 305,858 Year Ended December 31, 2018 Revenues - Outside $ 1,289,898 $ 643,898 $ — $ 69,061 $ — $ 2,002,857 Revenues - Intercompany 31,191 67 — 12,431 (43,689) — Total revenues (2) 1,321,089 643,965 — 81,492 (43,689) 2,002,857 Segment Adjusted EBITDA Expense (3) 796,370 398,243 — 52,321 (35,134) 1,211,800 Segment Adjusted EBITDA (4) 417,773 240,286 21,323 44,864 (8,555) 715,691 Total assets 1,380,912 440,518 161,312 589,010 (177,004) 2,394,748 Capital expenditures 166,468 64,037 — 2,975 — 233,480 Year Ended December 31, 2017 Revenues - Outside $ 1,069,767 $ 623,720 $ — $ 102,733 $ — $ 1,796,220 Revenues - Intercompany 56,097 2,321 — 12,016 (70,434) — Total revenues (2) 1,125,864 626,041 — 114,749 (70,434) 1,796,220 Segment Adjusted EBITDA Expense (3) 692,199 385,802 — 75,851 (61,665) 1,092,187 Segment Adjusted EBITDA (4) 398,080 234,124 13,297 45,296 (8,769) 682,028 Total assets 1,437,627 470,892 147,970 349,918 (187,036) 2,219,371 Capital expenditures 94,374 48,358 — 2,356 — 145,088 (1) The elimination column represents the elimination of intercompany transactions and is primarily comprised of sales from the Matrix Group to our mining operations, coal sales and purchases between operations within different segments, sales of receivables to AROP Funding, financing between segments and insurance premiums paid to Wildcat Insurance. (2) Revenues included in the Other and Corporate column are primarily attributable to the outside and affiliate revenues at the Matrix Group and coal brokerage activities. In additions, Other and Corporate includes affiliate revenues for administrative and Wildcat Insurance services. (3) Segment Adjusted EBITDA Expense includes operating expenses, coal purchases and other income. Transportation expenses are excluded as transportation revenues are recognized in an amount equal to transportation expenses when title passes to the customer. The following is a reconciliation of consolidated Segment Adjusted EBITDA Expense to Operating expenses (excluding depreciation, depletion and amortization) Year Ended December 31, 2019 2018 2017 (in thousands) Segment Adjusted EBITDA Expense $ 1,204,896 $ 1,211,800 $ 1,092,187 Outside coal purchases (23,357) (1,466) — Other income (expense) 561 (2,621) (332) Operating expenses (excluding depreciation, depletion and amortization) $ 1,182,100 $ 1,207,713 $ 1,091,855 (4) Segment Adjusted EBITDA is defined as net income attributable to ARLP before net interest expense, income taxes, depreciation, depletion and amortization, general and administrative expense, settlement gain, debt extinguishment loss, asset impairment and acquisition gain. Management therefore is able to focus solely on the evaluation of segment operating profitability as it relates to our revenues and operating expenses, which are primarily controlled by our segments. Consolidated Segment Adjusted EBITDA is reconciled to net income as follows: Year Ended December 31, 2019 2018 2017 (in thousands) Consolidated Segment Adjusted EBITDA $ 672,001 $ 715,691 $ 682,028 General and administrative (72,997) (68,298) (61,760) Depreciation, depletion and amortization (309,075) (280,225) (268,981) Settlement gain — 80,000 — Asset impairment (15,190) (40,483) — Interest expense, net (45,496) (40,059) (39,291) Acquisition gain 177,043 — — Debt extinguishment loss — — (8,148) Income tax (expense) benefit 211 (22) (210) Acquisition gain attributable to noncontrolling interest (7,083) — — Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Noncontrolling interest 7,512 866 563 Net income $ 406,926 $ 367,470 $ 304,201 . (5) Capital Expenditures shown exclude the AllDale Acquisition on January 3, 2019 and the Wing Acquisition on August 2, 2019 (Note 3 – Acquisitions).
Reconciliation of consolidated Segment Adjusted EBITDA Expense to operating expenses (excluding depreciation, depletion and amortization)	Year Ended December 31, 2019 2018 2017 (in thousands) Segment Adjusted EBITDA Expense $ 1,204,896 $ 1,211,800 $ 1,092,187 Outside coal purchases (23,357) (1,466) — Other income (expense) 561 (2,621) (332) Operating expenses (excluding depreciation, depletion and amortization) $ 1,182,100 $ 1,207,713 $ 1,091,855
Reconciliation of consolidated Segment Adjusted EBITDA to net income	Year Ended December 31, 2019 2018 2017 (in thousands) Consolidated Segment Adjusted EBITDA $ 672,001 $ 715,691 $ 682,028 General and administrative (72,997) (68,298) (61,760) Depreciation, depletion and amortization (309,075) (280,225) (268,981) Settlement gain — 80,000 — Asset impairment (15,190) (40,483) — Interest expense, net (45,496) (40,059) (39,291) Acquisition gain 177,043 — — Debt extinguishment loss — — (8,148) Income tax (expense) benefit 211 (22) (210) Acquisition gain attributable to noncontrolling interest (7,083) — — Net income attributable to ARLP $ 399,414 $ 366,604 $ 303,638 Noncontrolling interest 7,512 866 563 Net income $ 406,926 $ 367,470 $ 304,201

ORGANIZATION AND PRESENTATION (

ORGANIZATION AND PRESENTATION (Details)	Aug. 02, 2019a	Feb. 08, 2019a	Jan. 03, 2019a	May 31, 2018shares	Jul. 28, 2017shares	Dec. 31, 2019shares
AllDale I and II
Ownership interests
Royalty acres, net \| a			43,000
Wing
Ownership interests
Royalty acres controlled \| a		55,700
Royalty acres, net \| a	9,000
Royalty acres, gross \| a	400,000
SGP \| AHGP
Ownership interests
Ownership percentage by limited partners						34.48%
Exchange Transaction
Ownership interests
Common units issued in exchange						56,128,141
Exchange Transaction \| MGP
Ownership interests
Common units issued in exchange					56,100,000
Exchange Transaction \| SGP
Ownership interests
Common units issued in exchange					28,141
Exchange Transaction \| SGP \| ARLP
Ownership interests
Ownership percentage by general partners					0.01%
Simplification Transactions
Ownership interests
Issuance of units to Owners of SGP in Simplification Transactions (in units)						1,322,388
Simplification Transactions \| SGP
Ownership interests
Common units issued in exchange				29,188,997
Issuance of units to Owners of SGP in Simplification Transactions (in units)				1,322,388
Simplification Transactions \| AHGP
Ownership interests
Units issued in exchange (in units)				1.4782
Simplification Transactions \| Intermediate Partnership
Ownership interests
Ownership percentage by general partners				1.0001%
Simplification Transactions \| Alliance Coal
Ownership interests
Ownership percentage by general partners				0.001%
Simplification Transactions \| AHGP
Ownership interests
Approved written consent percent				68.00%
Units issued in exchange (in units)				1.4782
Simplification Transactions \| AHGP \| Intermediate Partnership
Ownership interests
Ownership percentage by general partners				1.0001%
Simplification Transactions \| AHGP \| Alliance Coal
Ownership interests
Ownership percentage by general partners				0.001%
Simplification Transactions \| SGP \| Intermediate Partnership
Ownership interests
Ownership percentage by general partners				1.0001%
Simplification Transactions \| SGP \| Alliance Coal
Ownership interests
Ownership percentage by general partners				0.001%

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash and Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Management
Book overdrafts			$ 14
Goodwill
Impairments of goodwill	$ 0	$ 0

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Tangible Assets (Details)	12 Months Ended
	Dec. 31, 2019
Preparation plants, processing facilities and mineral rights \| Minimum
Property, Plant and Equipment
Estimated useful life	1 year
Preparation plants, processing facilities and mineral rights \| Maximum
Property, Plant and Equipment
Estimated useful life	28 years
Other plant and equipment and mining equipment \| Minimum
Property, Plant and Equipment
Estimated useful life	1 year
Other plant and equipment and mining equipment \| Maximum
Property, Plant and Equipment
Estimated useful life	28 years
Buildings, office equipment and improvements \| Minimum
Property, Plant and Equipment
Estimated useful life	1 year
Buildings, office equipment and improvements \| Maximum
Property, Plant and Equipment
Estimated useful life	25 years

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets
Amortization expense attributable to intangible assets	$ 9,100	$ 6,900	$ 10,500
Original Cost	43,674	34,197
Accumulated Amortization	(34,005)	(24,919)
Intangibles, Net	9,669	9,278
Estimated amortization expense attributable to intangible assets
2020	4,495
2021	2,952
2022	647
2023	647
2024	66
Thereafter	862
Noncompete agreement
Intangible Assets
Original Cost	9,803	9,697
Accumulated Amortization	(9,440)	(8,385)
Intangibles, Net	363	1,312
Customer contracts, net
Intangible Assets
Original Cost	32,371	23,000
Accumulated Amortization	(24,258)	(16,293)
Intangibles, Net	8,113	6,707
Permits
Intangible Assets
Original Cost	1,500	1,500
Accumulated Amortization	(307)	(241)
Intangibles, Net	$ 1,193	$ 1,259

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Advance Royalties (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Advance Royalties
Advance royalties, net, affiliates	$ 41,216	$ 32,645
Advance royalties, net, third-parties	12,685	11,552
Total advance royalties, net	$ 53,901	$ 44,197

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Income Taxes
Percentage of qualifying income for tax purposes	90.00%
Assets and Liabilities, Lessee
Operating lease liabilities	$ 17,567
Offsetting right-of-use assets	$ 17,660
Minimum
Revenue Recognition
Coal shipments, payment period	14 days
Maximum
Revenue Recognition
Coal shipments, payment period	28 days
Defined benefit pension plan
Employee Benefit Plans
Threshold for amortization of unrecognized actuarial gains and losses (as a percent)	10.00%

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - New accounting standards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 17,660
Operating lease liabilities	$ 17,567
Lease, Practical Expedients, Package [true false]	true
Lease, Practical Expedient, Use of Hindsight [true false]	true
ASU 2016-02 \| Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 25,000
Operating lease liabilities		$ 25,000

ACQUISITIONS - Consideration (D

ACQUISITIONS - Consideration (Details) $ in Thousands	Aug. 02, 2019USD ($)a	Jan. 03, 2019USD ($)a	Dec. 31, 2019USD ($)	Jan. 02, 2019USD ($)	Dec. 31, 2018USD ($)
ACQUISITIONS
Previously held investment			$ 307,322
Equity method investments			28,529		$ 161,309
Acquisition gain			$ 177,043
AllDale I and II
ACQUISITIONS
Royalty acres, net \| a		43,000
Cash		$ 176,205
Previously held investment		307,322
Total		483,527
Equity method investments				$ 130,300
Acquisition gain		$ 177,000
Wing
ACQUISITIONS
Royalty acres, net \| a	9,000
Royalty acres, gross \| a	400,000
Cash	$ 144,900

ACQUISITIONS - Assets and Liabi

ACQUISITIONS - Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Aug. 02, 2019	Jan. 03, 2019
Wing
Assets acquired and liabilities assumed
Mineral interests in proved properties.			$ 58,084
Mineral interests in unproved properties			84,976
Receivables			1,867
Net assets acquired			144,927
Wing \| Preliminary
Assets acquired and liabilities assumed
Mineral interests in proved properties.			55,619
Mineral interests in unproved properties			87,441
Receivables			1,867
Net assets acquired			144,927
Wing \| Adjustments
Assets acquired and liabilities assumed
Mineral interests in proved properties.			2,465
Mineral interests in unproved properties			$ (2,465)
AllDale I and II
Assets acquired and liabilities assumed
Cash and cash equivalents	$ 900
Mineral interests in proved properties.	184,032
Mineral interests in unproved properties	291,190
Receivables	9,326
Accounts payable	(1,921)
Net assets acquired	483,527
Noncontrolling interest fair value				$ 12,300
AllDale I and II \| Preliminary
Assets acquired and liabilities assumed
Cash and cash equivalents				900
Mineral interests in proved properties.				159,617
Mineral interests in unproved properties				314,084
Receivables				10,602
Accounts payable				(1,921)
Net assets acquired				$ 483,282
AllDale I and II \| Adjustments
Assets acquired and liabilities assumed
Mineral interests in proved properties.	24,415
Mineral interests in unproved properties	(22,894)
Receivables	$ (1,276)	$ 1,300
Bluegrass Minerals \| Cavalier Minerals
Assets acquired and liabilities assumed
Noncontrolling ownership interest (as a percent)	4.00%			4.00%

ACQUISITIONS - Pro Forma (Detai

ACQUISITIONS - Pro Forma (Details) - USD ($) $ in Thousands	12 Months Ended
ACQUISITIONS - Pro Forma (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pro forma condensed consolidated income statement
Total revenues, As reported	$ 1,961,720	$ 2,002,857	$ 1,796,220
Net income	406,926	367,470	$ 304,201
Wing
Acquisitions, additional information
Revenue of acquired business	4,625
Net income of acquired business	1,291
Pro forma condensed consolidated income statement
Total revenues, As reported	1,961,720	2,002,857
Total revenues, Pro forma	1,966,291	2,008,559
Net income	406,926	367,470
Net income, Pro forma	411,217	372,810
AllDale I and II
Acquisitions, additional information
Revenue of acquired business	48,411
Net income of acquired business	$ 18,543
Pro forma condensed consolidated income statement
Total revenues, As reported		2,002,857
Total revenues, Pro forma		2,042,545
Net income		367,470
Net income, Pro forma		$ 358,741

LONG-LIVED ASSET IMPAIRMENTS (D

LONG-LIVED ASSET IMPAIRMENTS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Aug. 16, 2019	Aug. 15, 2019	Sep. 30, 2018
Asset impairment charges
Property, plant and equipment	$ 1,412,358	$ 2,008,986	$ 1,412,358
Asset impairment		15,190	40,483
Dotiki Mine
Asset impairment charges
Property, plant and equipment	51,000		$ 51,000	$ 25,800	$ 35,900	$ 85,300
Accrued payments				$ 5,100
Asset impairment	34,300	$ 15,200
Coal reserves not to exercise lease option
Asset impairment charges
Asset impairment	$ 6,200

INVENTORIES (Details)

INVENTORIES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
INVENTORIES
Coal	$ 63,645	$ 20,929
Supplies (net of reserve for obsolescence of $5,564 and $5,453, respectively)	37,660	38,277
Total inventories, net	101,305	59,206
Reserve for obsolescence	$ 5,555	$ 5,453

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost	$ 2,925,808	$ 3,684,008
Less accumulated depreciation, depletion and amortization	(1,513,450)	(1,675,022)
Total property, plant and equipment, net	1,412,358	2,008,986
Mining equipment and processing facilities
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost	1,851,479	1,937,642
Land and coal mineral rights
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost	445,411	453,237
Coal reserves not subject to depletion	49,200	40,100
Oil and gas mineral interests
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost		618,282
Unproved properties		376,200
Buildings, office equipment and improvements
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost	287,053	304,111
Construction and mine development in progress
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost	71,190	86,876
Mine development costs
PROPERTY, PLANT AND EQUIPMENT
Property, plant and equipment, at cost	270,675	283,860
Capitalized development costs of mines in development phase		$ 13,200
Decrease in mine development costs	$ 9,900

LONG-TERM DEBT - Components (De

LONG-TERM DEBT - Components (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Apr. 24, 2017
Principal
Aggregate maturities of long-term debt	$ 789,280	$ 667,000
Less current maturities	(13,157)	(92,000)
Total long-term debt	776,123	575,000
Unamortized Discount and Debt Issuance Costs
Unamortized debt issuance costs including current and non-current	(7,929)	(10,996)
Total unamortized debt issuance costs	(7,929)	(10,996)
Revolving credit facility
Principal
Aggregate maturities of long-term debt	255,000	175,000
Unamortized Discount and Debt Issuance Costs
Unamortized debt issuance costs including current and non-current	(3,050)	(5,203)
Senior notes due 2025
Principal
Aggregate maturities of long-term debt	400,000	400,000
Unamortized Discount and Debt Issuance Costs
Unamortized debt issuance costs including current and non-current	(4,879)	(5,793)	$ (7,300)
Securitization Facility
Principal
Aggregate maturities of long-term debt	73,800	$ 92,000
Equipment Financing May 2019
Principal
Aggregate maturities of long-term debt	8,199
Equipment Financing November 2019
Principal
Aggregate maturities of long-term debt	$ 52,281

LONG-TERM DEBT - Credit Facilit

LONG-TERM DEBT - Credit Facility (Details) $ in Thousands	Jan. 27, 2017USD ($)item	Dec. 31, 2019USD ($)	Dec. 31, 2017USD ($)
Long-Term Debt
Debt issuance costs incurred			$ 16,487
Credit Agreement
Long-Term Debt
Debt issuance costs incurred			$ 9,200
Number of benchmarks \| item	3
ARLP debt arrangements requirements, debt to cash flow ratio	2.5
ARLP debt arrangements requirements, cash flow to interest expense ratio	3
ARLP debt arrangements requirements, period over which the ratios are required to be maintained	12 months
Actual debt to cash flow ratio for trailing twelve months		1.34
Actual cash flow to interest expense ratio for trailing twelve months		12.6
Credit Agreement \| Eurodollar Rate
Long-Term Debt
Effective interest rate (as a percent)		4.32%
Revolving credit facility
Long-Term Debt
Maximum borrowing capacity	$ 494,750
Line of credit facility, available for borrowing		$ 230,500
Annual commitment fee percentage, undrawn portion		0.35%
Letters of credit subfacility
Long-Term Debt
Maximum borrowing capacity	125,000
Letters of credit outstanding		$ 9,300
Swingline subfacility
Long-Term Debt
Maximum borrowing capacity	$ 15,000

LONG-TERM DEBT - 2025 Senior No

LONG-TERM DEBT - 2025 Senior Notes (Details) - USD ($) $ in Thousands	Apr. 24, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Issuance of Senior Notes
Make-whole payment		$ 8,148
Discount and debt issuance costs incurred			$ 7,929	$ 10,996
Senior notes due 2025
Issuance of Senior Notes
Principal amount	$ 400,000
Term	8 years
Interest rate (as a percent)	7.50%
Percentage of debt that may be redeemed prior to May 1, 2020	35.00%
Redemption price expressed as a percentage of principal	107.50%
Make-whole payment	$ 8,100
Discount and debt issuance costs incurred	$ 7,300		$ 4,879	$ 5,793

LONG-TERM DEBT - Securitization

LONG-TERM DEBT - Securitization Facility (Details) - Securitization Facility - USD ($)	Dec. 31, 2019	Dec. 05, 2014
Long-Term Debt
Maximum borrowing capacity		$ 100,000,000
Facility outstanding amount	$ 73,800,000

LONG-TERM DEBT - Cavalier and O

LONG-TERM DEBT - Cavalier and Other (Details) - Letters of credit - Other $ in Millions	Dec. 31, 2019USD ($)
Long-Term Debt
Credit facility amount	$ 5
Letters of Credit Outstanding, Amount	$ 5

LONG-TERM DEBT - Equipment fina

LONG-TERM DEBT - Equipment financing and other (Details) $ in Millions	Nov. 06, 2019USD ($)payment	May 17, 2019USD ($)
May 2019 Equipment Financing
Long-Term Debt
Principal amount		$ 10
Term		36 months
Effective interest rate (as a percent)		6.25%
November 2019 Equipment Financing
Long-Term Debt
Principal amount	$ 53.1
Term	4 years
Effective interest rate (as a percent)	4.75%
Number of monthly payments \| payment	47
Periodic Payment	$ 1
Balloon payment on maturity	$ 11.6

LONG-TERM DEBT - Maturities (De

LONG-TERM DEBT - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Aggregate maturities of long-term debt
2020	$ 13,157
2021	342,648
2022	12,403
2023	21,072
Thereafter	400,000
Aggregate maturities of long-term debt	$ 789,280	$ 667,000

LEASES - Lease expense (Details

LEASES - Lease expense (Details) - USD ($) $ in Thousands	12 Months Ended
LEASES - Lease expense (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
LEASES
Amortization of right-of-use assets	$ 14,608
Interest on lease liabilities	2,085
Operating lease cost	9,169
Short-term lease cost	464
Variable lease cost	1,360
Total lease cost	27,686
Rental expense	$ 11,000	$ 14,900	$ 16,000

LEASES - Cash flow (Details)

LEASES - Cash flow (Details) - USD ($) $ in Thousands	12 Months Ended
LEASES - Cash flow (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
LEASES
Operating cash flows for operating leases	$ 9,124
Operating cash flows for finance leases	891
Financing cash flows for finance leases	46,725	$ 29,353	$ 27,071
Operating leases, Right-of-use assets obtained in exchange for lease obligations	$ 25,593

LEASES - Balance Sheet (Details

LEASES - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
PROPERTY, PLANT AND EQUIPMENT:
Property, plant and equipment, at cost	$ 3,684,008	$ 2,925,808
Less accumulated depreciation, depletion and amortization	(1,675,022)	(1,513,450)
Total property, plant and equipment, net	2,008,986	1,412,358
Assets under finance lease
PROPERTY, PLANT AND EQUIPMENT:
Property, plant and equipment, at cost	30,610	141,019
Less accumulated depreciation, depletion and amortization	(20,564)	(74,576)
Total property, plant and equipment, net	$ 10,046	$ 66,443

LEASES - Weighted Average (Deta

LEASES - Weighted Average (Details)	Dec. 31, 2019
LEASES
Weighted average remaining lease term of operating leases	13 years 1 month 6 days
Weighted average remaining lease term of finance leases	1 year 7 months 6 days
Weighted average discount rate of operating leases (as a percent)	6.00%
Weighted average discount rate of finance leases (as a percent)	6.00%

LEASES - Maturities (Details)

LEASES - Maturities (Details) $ in Thousands	Dec. 31, 2019USD ($)
Operating leases
2020	$ 3,832
2021	2,280
2022	2,217
2023	2,040
2024	1,820
Thereafter	13,539
Total lease payments	25,728
Less imputed interest	(8,161)
Total	17,567
Finance leases
2020	8,747
2021	912
2022	912
2023	139
2024	139
Thereafter	419
Total lease payments	11,268
Less imputed interest	(676)
Total	$ 10,592

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - Estimated fair value - Significant Observable Inputs (Level 2) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
FAIR VALUE MEASUREMENTS
Long-term debt	$ 736,206	$ 669,864
Total	$ 736,206	$ 669,864

PARTNERS' CAPITAL - Distributio

PARTNERS' CAPITAL - Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands

Feb. 14, 2020

Jan. 27, 2020

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Jun. 30, 2017

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Distribution Made to Member or Limited Partner

Period following quarter end for distribution of available cash

45 days

Quarterly distribution paid (in dollars per unit)

$ 0.5400

$ 0.5350

$ 0.5300

$ 0.5250

$ 0.5200

$ 0.5150

$ 0.5100

$ 0.5050

$ 0.5000

$ 0.4375

Total Cash Distribution

$ 278,425

$ 275,902

$ 240,812

Distribution declared (in dollars per unit)

$ 0.40

Quarterly distribution paid (in dollars per unit)

$ 0.40

Quarterly distribution declared

$ 50,800

Quarterly distribution paid

$ 50,800

Percentage of available cash distributed

100.00%

MGP

Distribution Made to Member or Limited Partner

Managing general partner incentive distributions (in dollars)

$ 37,600

MGP | Excess Of $0.1375 Per Unit

Distribution Made to Member or Limited Partner

Threshold distribution of net income per unit (in dollars per unit)

$ 0.1375

General partner incentive distribution (as a percent)

15.00%

MGP | Excess Of $0.15625 Per Unit

Distribution Made to Member or Limited Partner

Threshold distribution of net income per unit (in dollars per unit)

$ 0.15625

General partner incentive distribution (as a percent)

25.00%

MGP | Excess Of $0.1875 Per Unit

Distribution Made to Member or Limited Partner

Threshold distribution of net income per unit (in dollars per unit)

$ 0.1875

General partner incentive distribution (as a percent)

50.00%

PARTNERS' CAPITAL - Narrative (

PARTNERS' CAPITAL - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 29, 2018	May 31, 2018	Jul. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Partners' capital
Cash contribution by affiliated entity					$ 2,142
Affiliated entity controlled by Mr. Craft
Partners' capital
Contribution of units by affiliated entity (in units)	467,018
Cash contribution by affiliated entity					$ 2,100	$ 1,000
MGP \| ARLP
Partners' capital
Ownership percentage by general partners				0.99%
MGP \| Intermediate Partnership
Partners' capital
Ownership percentage by general partners				1.0001%
MGP \| Alliance Coal
Partners' capital
Ownership percentage by general partners				0.001%
Limited Partners' Capital
Partners' capital
Issuance of units to Owners of SGP in Simplification Transactions (in units)					1,322,388
Repurchase and retire authorization		$ 100,000
Number of units retired				5,460,639
Repurchase price (in dollars per unit)				$ 17.12
Aggregate treasury units retired				$ 93,500
Contribution of units by affiliated entity (in units)					(467,018)
Exchange Transaction
Partners' capital
Common units issued in exchange				56,128,141
Exchange Transaction \| MGP
Partners' capital
Common units issued in exchange			56,100,000
Exchange Transaction \| SGP
Partners' capital
Common units issued in exchange			28,141
Exchange Transaction \| MGP \| ARLP
Partners' capital
Ownership percentage by general partners			0.99%
Exchange Transaction \| SGP \| ARLP
Partners' capital
Ownership percentage by general partners			0.01%
Exchange Transaction \| General Partner's Capital (Deficit)
Partners' capital
Partners' capital, Exchange Transaction reclassification				$ 306,700
Exchange Transaction \| Limited Partners' Capital
Partners' capital
Partners' capital, Exchange Transaction reclassification				$ (306,700)
Simplification Transactions
Partners' capital
Issuance of units to Owners of SGP in Simplification Transactions (in units)				1,322,388
Simplification Transactions \| Intermediate Partnership
Partners' capital
Ownership percentage by general partners		1.0001%
Simplification Transactions \| Alliance Coal
Partners' capital
Ownership percentage by general partners		0.001%
Simplification Transactions \| SGP
Partners' capital
Common units issued in exchange		29,188,997
Issuance of units to Owners of SGP in Simplification Transactions (in units)		1,322,388
Simplification Transactions \| MGP \| Intermediate Partnership
Partners' capital
Ownership percentage by general partners		1.0001%
Simplification Transactions \| MGP \| Alliance Coal
Partners' capital
Ownership percentage by general partners		0.001%
Simplification Transactions \| SGP \| Intermediate Partnership
Partners' capital
Ownership percentage by general partners		1.0001%
Simplification Transactions \| SGP \| Alliance Coal
Partners' capital
Ownership percentage by general partners		0.001%
Simplification Transactions \| Limited Partners' Capital
Partners' capital
Number of units retired				35

VARIABLE INTEREST ENTITIES - Ca

VARIABLE INTEREST ENTITIES - Cavalier (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 03, 2019
Variable Interest Entities
Contributions		$ 2,142
Distributions paid to Partners	$ 278,425	$ 275,902	$ 240,812
Cavalier Minerals \| Bluegrass Minerals
Variable Interest Entities
Contributions	5,963
Distributions paid to Partners	$ 2,996
Cavalier Minerals \| Bluegrass Minerals
Variable Interest Entities
Incentive distribution of available cash (as a percent)	25.00%
Cavalier Minerals
Variable Interest Entities
Ownership interest in VIE (as a percent)	96.00%
Cavalier Minerals \| Bluegrass Minerals
Variable Interest Entities
Noncontrolling ownership interest (as a percent)	4.00%			4.00%
Cavalier Minerals \| Cavalier Minerals
Variable Interest Entities
Contributions	$ 143,112
Distributions paid to Partners	$ 71,916

VARIABLE INTEREST ENTITIES - Al

VARIABLE INTEREST ENTITIES - All Dale III (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 28, 2017
Equity Investments
Investments in affiliate	$ 28,529	$ 161,309
Percentage of available cash distributed	100.00%
All Dale Minerals III
Equity Investments
Investments in affiliate	$ 28,529	28,974	$ 14,182
Other Commitment				$ 30,000
Distribution after hurdles (as a percent)	25.00%
Specified internal rate of return (as a percent)	10.00%
Percentage of available cash distributed	125.00%
Distributions received	$ 2,648	$ 1,355
All Dale Minerals III \| All Dale Minerals III
Equity Investments
Ownership percentage by limited partners	13.90%

VARIABLE INTEREST ENTITIES - WK

VARIABLE INTEREST ENTITIES - WKY CoalPlay (Details)	Nov. 17, 2014company
WKY CoalPlay
Variable Interest Entities
Number of limited liability companies related to MGP, that formed the related party together with SGP Land	2

INVESTMENTS - AllDale (Details)

INVESTMENTS - AllDale (Details) - USD ($) $ in Thousands	12 Months Ended
INVESTMENTS - AllDale (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in equity method investment
Beginning balance	$ 161,309
Equity method investment income (loss)	2,203	$ 22,189	$ 13,860
Ending balance	28,529	161,309
All Dale Minerals III
Changes in equity method investment
Beginning balance	28,974	14,182
Contributions		15,600	14,400
Equity method investment income (loss)	2,203	547	(218)
Distributions received	(2,648)	(1,355)
Ending balance	$ 28,529	$ 28,974	$ 14,182

INVESTMENTS - Kodiak (Details)

INVESTMENTS - Kodiak (Details) - USD ($) $ in Thousands	Feb. 08, 2019	Dec. 31, 2019	Dec. 31, 2018	Jul. 19, 2017
Equity securities without readily determinable fair value
Equity securities			$ 122,094
Redemption of preferred interest		$ 134,288
Kodiak
Equity securities without readily determinable fair value
Equity securities	$ 0			$ 100,000
Redemption of preferred interest	135,000
Gain on redemption	$ 11,500

REVENUE FROM CONTRACTS WITH C_3

REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation of revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of revenues
Revenues	$ 1,961,720	$ 2,002,857	$ 1,796,220
Coal sales
Disaggregation of revenues
Revenues	1,762,442	1,844,808	1,711,114
Oil & gas royalties
Disaggregation of revenues
Revenues	51,735
Transportation revenues
Disaggregation of revenues
Revenues	99,503	112,385	41,700
Other revenues
Disaggregation of revenues
Revenues	48,040	45,664	43,406
Illinois Basin
Disaggregation of revenues
Revenues	1,236,308	1,321,089	1,125,864
Illinois Basin \| Coal sales
Disaggregation of revenues
Revenues	1,128,588	1,197,143	1,078,255
Illinois Basin \| Transportation revenues
Disaggregation of revenues
Revenues	94,686	106,947	35,585
Illinois Basin \| Other revenues
Disaggregation of revenues
Revenues	13,034	16,999	12,024
Appalachia
Disaggregation of revenues
Revenues	644,389	643,965	626,041
Appalachia \| Coal sales
Disaggregation of revenues
Revenues	628,406	635,530	616,305
Appalachia \| Transportation revenues
Disaggregation of revenues
Revenues	4,817	5,435	6,115
Appalachia \| Other revenues
Disaggregation of revenues
Revenues	11,166	3,000	3,621
Minerals
Disaggregation of revenues
Revenues	53,036
Minerals \| Oil & gas royalties
Disaggregation of revenues
Revenues	51,735
Minerals \| Other revenues
Disaggregation of revenues
Revenues	1,301
Other and Corporate
Disaggregation of revenues
Revenues	56,850	81,492	114,749
Other and Corporate \| Coal sales
Disaggregation of revenues
Revenues	22,138	43,393	74,973
Other and Corporate \| Transportation revenues
Disaggregation of revenues
Revenues		3
Other and Corporate \| Other revenues
Disaggregation of revenues
Revenues	34,712	38,096	39,776
Operating segments
Disaggregation of revenues
Revenues	1,961,720	2,002,857	1,796,220
Operating segments \| Illinois Basin
Disaggregation of revenues
Revenues	1,219,618	1,289,898	1,069,767
Operating segments \| Appalachia
Disaggregation of revenues
Revenues	644,389	643,898	623,720
Operating segments \| Minerals
Disaggregation of revenues
Revenues	53,036
Operating segments \| Other and Corporate
Disaggregation of revenues
Revenues	44,677	69,061	102,733
Elimination
Disaggregation of revenues
Revenues	(28,863)	(43,689)	(70,434)
Elimination \| Coal sales
Disaggregation of revenues
Revenues	(16,690)	(31,258)	(58,419)
Elimination \| Other revenues
Disaggregation of revenues
Revenues	(12,173)	(12,431)	(12,015)
Elimination \| Illinois Basin
Disaggregation of revenues
Revenues	16,690	31,191	56,097
Elimination \| Appalachia
Disaggregation of revenues
Revenues		67	2,321
Elimination \| Other and Corporate
Disaggregation of revenues
Revenues	$ 12,173	$ 12,431	$ 12,016

REVENUE FROM CONTRACTS WITH C_4

REVENUE FROM CONTRACTS WITH CUSTOMERS - Coal supply contracts (Details) $ in Thousands	Dec. 31, 2019USD ($)
Performance obligations unsatisfied or partially unsatisfied
Total	$ 1,907,755
Illinois Basin
Performance obligations unsatisfied or partially unsatisfied
Total	1,329,732
Appalachia
Performance obligations unsatisfied or partially unsatisfied
Total	578,023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Performance obligations unsatisfied or partially unsatisfied
Total	$ 1,275,202
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 \| Illinois Basin
Performance obligations unsatisfied or partially unsatisfied
Total	$ 849,040
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 \| Appalachia
Performance obligations unsatisfied or partially unsatisfied
Total	$ 426,162
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Performance obligations unsatisfied or partially unsatisfied
Total	$ 535,537
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 \| Illinois Basin
Performance obligations unsatisfied or partially unsatisfied
Total	$ 437,808
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 \| Appalachia
Performance obligations unsatisfied or partially unsatisfied
Total	$ 97,729
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Performance obligations unsatisfied or partially unsatisfied
Total	$ 88,546
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Illinois Basin
Performance obligations unsatisfied or partially unsatisfied
Total	$ 34,414
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 \| Appalachia
Performance obligations unsatisfied or partially unsatisfied
Total	$ 54,132
Expected timing of satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Performance obligations unsatisfied or partially unsatisfied
Total	$ 8,470
Expected timing of satisfaction period
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Illinois Basin
Performance obligations unsatisfied or partially unsatisfied
Total	$ 8,470
Expected timing of satisfaction period
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 \| Appalachia
Performance obligations unsatisfied or partially unsatisfied
Expected timing of satisfaction period

EARNINGS PER LIMITED PARTNER _3

EARNINGS PER LIMITED PARTNER UNIT - Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	May 31, 2018	Jul. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to ARLP			$ 399,414	$ 366,604	$ 303,638
MGP's priority distributions					(19,216)
General partner's equity ownership				(1,560)	(3,688)
General partner's special allocation of certain general and administrative expenses					1,000
LIMITED PARTNERS			399,414	365,044	281,734
Distributions to participating securities			(4,254)	(5,114)	(4,339)
Undistributed earnings attributable to participating securities			(2,237)	(1,641)	(1,026)
Net income attributable to ARLP available to limited partners			$ 392,923	$ 358,289	$ 276,369
Weighted-average limited partner units outstanding - basic and diluted			128,116,670	130,758,169	98,707,696
EARNINGS PER LIMITED PARTNER UNIT - BASIC AND DILUTED			$ 3.07	$ 2.74	$ 2.80
Anti-dilutive under the treasury stock method (in units)			1,284,013	1,658,908	1,466,404
MGP
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Contributions from affiliates for general and administrative expenses					$ 1,000
MGP \| ARLP
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners			0.99%
MGP \| Intermediate Partnership
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners			1.0001%
MGP \| Alliance Coal
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners			0.001%
Pro Forma
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to ARLP			$ 399,414	$ 366,604	303,638
Pro forma adjustments				(1,265)	(1,943)
LIMITED PARTNERS			399,414	365,339	301,695
Distributions to participating securities			(4,254)	(5,114)	(4,339)
Undistributed earnings attributable to participating securities			(2,237)	(1,627)	(680)
Net income attributable to ARLP available to limited partners			$ 392,923	$ 358,598	$ 296,676
Weighted-average limited partner units outstanding - basic and diluted			128,117,000	131,310,000	132,024,000
EARNINGS PER LIMITED PARTNER UNIT - BASIC AND DILUTED			$ 3.07	$ 2.73	$ 2.25
Anti-dilutive under the treasury stock method (in units)			1,284,013	1,658,908	1,466,404
Exchange Transaction
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common units issued in exchange			56,128,141
Exchange Transaction \| MGP \| ARLP
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners		0.99%
Simplification Transactions
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Issuance of units to Owners of SGP in Simplification Transactions (in units)			1,322,388
Simplification Transactions \| Intermediate Partnership
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners	1.0001%
Simplification Transactions \| Alliance Coal
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners	0.001%
Simplification Transactions \| AHGP \| Intermediate Partnership
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners	1.0001%
Simplification Transactions \| AHGP \| Alliance Coal
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners	0.001%
Simplification Transactions \| MGP \| Intermediate Partnership
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners	1.0001%
Simplification Transactions \| MGP \| Alliance Coal
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Ownership percentage by general partners	0.001%
SGP \| Exchange Transaction
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common units issued in exchange		28,141
SGP \| Simplification Transactions
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common units issued in exchange	29,188,997
Issuance of units to Owners of SGP in Simplification Transactions (in units)	1,322,388
MGP \| Exchange Transaction
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common units issued in exchange		56,100,000

EMPLOYEE BENEFIT PLANS - Define

EMPLOYEE BENEFIT PLANS - Defined Contribution (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
PSSP
Defined Contribution Plans
Contribution expense	$ 21.1	$ 19.9	$ 18.7

EMPLOYEE BENEFIT PLANS - Benefi

EMPLOYEE BENEFIT PLANS - Benefit Obligations, Plan Assets and Reported Amounts (Details) - Defined benefit pension plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in benefit obligations:
Benefit obligations at beginning of year	$ 118,958	$ 127,298
Interest cost	4,864	4,462	$ 4,587
Actuarial loss (gain)	17,084	(8,562)
Benefits paid	(4,481)	(4,240)
Benefit obligations at end of year	136,425	118,958	127,298
Change in plan assets:
Fair value of plan assets at beginning of year	75,823	81,981
Employer contribution	5,559	4,187
Actual return on plan assets	14,666	(6,105)
Benefits paid	(4,481)	(4,240)
Fair value of plan assets at end of year	91,567	75,823	$ 81,981
Funded status at the end of year	(44,858)	(43,135)
Amounts recognized in balance sheet:
Non-current liability	(44,858)	(43,135)
Amount recognized in accumulated other comprehensive income consists of:
Prior service cost	(940)	(1,126)
Net actuarial loss	(45,125)	(41,697)
Amounts recognized in accumulated other comprehensive income	$ (46,065)	$ (42,823)
Weighted-average assumption to determine benefit obligations
Discount rate	3.15%	4.17%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate	4.17%	3.54%
Expected return on plan assets	6.50%	7.00%

EMPLOYEE BENEFIT PLANS - Assump

EMPLOYEE BENEFIT PLANS - Assumptions (Details) - Defined benefit pension plan	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Asset allocation assumptions
Active management premium percentage	1.50%
Asset allocation assumption	100.00%
Actual return on plan assets (as a percent)	19.20%	(6.70%)
Equity securities
Asset allocation assumptions
Asset allocation assumption	62.00%
Fixed income securities
Asset allocation assumptions
Asset allocation assumption	33.00%
Real estate
Asset allocation assumptions
Asset allocation assumption	5.00%

EMPLOYEE BENEFIT PLANS - Period

EMPLOYEE BENEFIT PLANS - Periodic Benefit Cost and Other Changes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss:
Total adjustments	$ (31,122)	$ 5,069	$ (13,400)
Defined benefit pension plan
Components of net periodic benefit cost:
Interest cost	4,864	4,462	4,587
Expected return on plan assets	(4,932)	(5,784)	(4,978)
Amortization of prior service cost	186	186	186
Amortization of net loss	3,922	3,608	3,054
Net periodic benefit cost	4,040	2,472	2,849
Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss:
Net actuarial loss	(7,350)	(3,326)	(6,610)
Reversal of amortization item: Prior service cost	186	186	186
Reversal of amortization item: net actuarial loss	3,922	3,608	3,054
Total adjustments	(3,242)	468	(3,370)
Net periodic benefit cost	(4,040)	(2,472)	$ (2,849)
Total recognized in net periodic benefit cost and accumulated other comprehensive loss	$ (7,282)	$ (2,004)

EMPLOYEE BENEFIT PLANS - Estima

EMPLOYEE BENEFIT PLANS - Estimated Benefit Payments (Details) - Defined benefit pension plan $ in Thousands	Dec. 31, 2019USD ($)
Estimated future benefit payments
2020	$ 5,288
2021	5,677
2022	6,045
2023	6,342
2024	6,507
2025-2029	34,755
Estimated future benefit payments	64,614
Expected contribution for pension plan in next year	$ 5,300

EMPLOYEE BENEFIT PLANS - Asset

EMPLOYEE BENEFIT PLANS - Asset Allocations (Details) - Defined benefit pension plan	Dec. 31, 2019
Equity securities
Employee Benefit Plans
Target allocation	62.00%
Equity securities \| Minimum
Employee Benefit Plans
Target allocation	45.00%
Equity securities \| Maximum
Employee Benefit Plans
Target allocation	80.00%
Fixed income securities
Employee Benefit Plans
Target allocation	33.00%
Fixed income securities \| Minimum
Employee Benefit Plans
Target allocation	10.00%
Fixed income securities \| Maximum
Employee Benefit Plans
Target allocation	55.00%
Real estate
Employee Benefit Plans
Target allocation	5.00%
Real estate \| Minimum
Employee Benefit Plans
Target allocation	0.00%
Real estate \| Maximum
Employee Benefit Plans
Target allocation	10.00%

EMPLOYEE BENEFIT PLANS - Fair V

EMPLOYEE BENEFIT PLANS - Fair Value of Plan Assets (Details) - Defined benefit pension plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	$ 91,567	$ 75,823	$ 81,981
Cash And Cash Equivalents \| Quoted Prices In Active Markets For Identical Assets (Level 1)
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	2,958	5,277
Equities - Global \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	10,028
Equities - United States large-cap \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	19,220	21,862
Equities - United States small-cap \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	7,592	5,259
Equities - International developed markets \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	10,528	10,593
Equities - International emerging markets \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	8,410	4,808
Fixed income - Investment grade \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	26,186	15,777
Fixed income - High yield \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets		4,508
Real estate \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	4,355	5,034
Pension Plan assets - Other \| Net asset value per share
Employee Benefit Plans
Defined benefit plan, fair value of plan assets	$ 2,290	$ 2,705

COMPENSATION PLANS - LTIP Grant

COMPENSATION PLANS - LTIP Grants Activity (Details) - ARLP LTIP - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of units
Balance at the beginning of the period (in units)	1,828,080	1,694,026	1,604,748
Granted (in units)	682,155	511,305	475,310
Vested (in units)	(885,381)	(331,502)	(350,516)
Forfeited (in units)	(21,476)	(45,749)	(35,516)
Balance at the end of the period (in units)	1,603,378	1,828,080	1,694,026
Weighted average grant date fair value per unit
Balance at the beginning of the period (in dollars per unit)	$ 17.18	$ 19.62	$ 23.19
Granted (in dollars per unit)	18.63	20.40	23.17
Vested (in dollars per unit)	12.38	34.61	40.73
Forfeited (in dollars per unit)	20.84	17.40	20.01
Balance at the end of the period (in dollars per unit)	$ 20.39	$ 17.18	$ 19.62
Intrinsic value (in dollars)
Intrinsic value of outstanding grants (in dollars)	$ 17,349	$ 31,699	$ 33,372	$ 36,027
Other information
Common units issued upon vesting	596,650	191,858	222,011

COMPENSATION PLANS - LTIP Other

COMPENSATION PLANS - LTIP Other Information (Details) - ARLP LTIP - USD ($) $ in Millions	Jan. 22, 2022	Feb. 10, 2020	Jan. 23, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other information
Unit-based compensation expense				$ 10.4	$ 10.8	$ 11
Total unit-based obligation recorded				20.2	$ 20.8
Unrecognized compensation expense (in dollars)				$ 12.5
Weighted-average period for recognition of expense				1 year 2 months 12 days
Units for which vesting requirements were deemed satisfied				885,381	331,502	350,516
Forfeitures (in units)				21,476	45,749	35,516
Common units issued upon vesting				596,650	191,858	222,011
Units available for grant				1,000,000
Units granted				682,155	511,305	475,310
2017 Grants
Other information
Units for which vesting requirements were deemed satisfied			424,486
Forfeitures (in units)			50,824
Common units issued upon vesting		279,622
Additional grants authorized (in units)	965,035
Units granted	950,035

COMPENSATION PLANS - SERP and D

COMPENSATION PLANS - SERP and Directors Compensation Activity (Details) - SERP and Directors' Compensation Plans - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other information
Unit-based compensation expense	$ 1,600	$ 1,600	$ 1,400
Total unit-based obligation recorded	$ 16,100	$ 17,400
Phantom Share Units (PSUs)
Summary of units
Balance at the beginning of the period (in units)	635,837	561,784	494,018
Granted (in units)	111,012	84,417	67,766
Issued (in units)	(115,484)	(10,364)
Balance at the end of the period (in units)	631,365	635,837	561,784
Weighted average grant date fair value per unit
Balance at the beginning of the period (in dollars per unit)	$ 27.34	$ 28.64	$ 29.77
Granted (in dollars per unit)	14.50	18.78	20.38
Issued (in dollars per unit)	25.20	27.92
Balance at the end of the period (in dollars per unit)	$ 25.48	$ 27.34	$ 28.64
Intrinsic value (in dollars)
Intrinsic value of outstanding grants (in dollars)	$ 6,831	$ 11,025	$ 11,067	$ 11,091
Other information
Common units issued upon vesting	115,484	7,181

SUPPLEMENTAL CASH FLOW INFORM_3

SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	Jan. 03, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Paid For:
Interest		$ 43,093	$ 38,450	$ 31,692
Income taxes			34	210
Non-Cash Activity:
Accounts payable for purchase of property, plant and equipment		14,504	14,585	15,636
Assets acquired by finance lease			835
Market value of common units issued under deferred compensation plans before tax withholding requirements		17,415	$ 6,142	$ 8,149
Acquisition of businesses
Fair value of assets assumed		629,475
Previously held equity-method investments		(307,322)
Cash paid, net of cash acquired		(320,232)
Fair value of liabilities assumed		1,921
Acquisition gain		$ 177,043
AllDale I and II
Acquisition of businesses
Previously held equity-method investments	$ (307,322)
Acquisition gain	$ 177,000

ASSET RETIREMENT OBLIGATIONS -

ASSET RETIREMENT OBLIGATIONS - Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Asset retirement and mine closing liability
Balance at the beginning of the period	$ 137,114	$ 130,600
Accretion expense	4,087	3,926	$ 3,793
Payments	(2,948)	(2,392)
Allocation of liability associated with acquisitions, mine development and change in assumptions	(739)	4,980
Balance at the end of the period	$ 137,514	$ 137,114	$ 130,600

ASSET RETIREMENT OBLIGATIONS _2

ASSET RETIREMENT OBLIGATIONS - Estimated Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Estimated payments of asset retirement obligations:
2020	$ 4,496
2021	2,576
2022	2,794
2023	2,027
2024	2,986
Thereafter	225,584
Aggregate undiscounted asset retirement obligations	240,463
Effect of discounting	(102,949)	$ (100,300)
Total asset retirement obligations	137,514	137,114	$ 130,600
Less: current portion	(4,496)
Asset retirement obligations	133,018	127,655
Surety bonds outstanding to performance of reclamation obligations	$ 181,600	$ 169,300

ACCRUED WORKERS' COMPENSATION_3

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS - Workers' Compensation Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of changes in the workers' compensation liability
Beginning balance	$ 49,539	$ 54,439
Accruals increase	7,162	7,654
Payments	(11,320)	(10,837)
Interest accretion	1,606	1,454
Valuation gain	6,397	(3,171)
Ending balance	$ 53,384	$ 49,539
Estimated present value of future obligations and other information
Workers' compensation discount rate	2.81%	3.89%
Letters of credit outstanding to secure workers compensation obligations	$ 90,200	$ 90,500
Other long-term assets
Estimated present value of future obligations and other information
Receivables for traumatic injury claims	$ 7,700	$ 8,100

ACCRUED WORKERS' COMPENSATION_4

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS - Benefit Obligations (Details) - Pneumoconiosis benefits - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of the changes in black lung benefit obligations
Benefit obligations at beginning of year	$ 72,095	$ 74,859
Service cost	2,593	2,525	$ 2,255
Interest cost	3,044	2,542	2,555
Actuarial (gain) loss	23,298	(4,599)
Benefits and expenses paid	(3,347)	(3,232)
Benefit obligations at end of year	$ 97,683	$ 72,095	$ 74,859

ACCRUED WORKERS' COMPENSATION_5

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS - Recognized in AOCL (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss:
Total adjustments	$ (31,122)	$ 5,069	$ (13,400)
Pneumoconiosis benefits
Other changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss:
Net actuarial loss	(23,298)	4,599	(7,938)
Reversal of amortization item: net actuarial gain	(4,582)	2	(2,092)
Total adjustments	$ (27,880)	$ 4,601	$ (10,030)
Estimated present value of future obligations and other information
Pneumoconiosis discount rate	3.12%	4.13%	3.49%
Amount recognized in accumulated other comprehensive income consists of:
Net actuarial loss	$ 31,927	$ 4,047	$ 8,648

ACCRUED WORKERS' COMPENSATION_6

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS - Recognized in Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS
Workers' compensation claims	$ 53,384	$ 49,539	$ 54,439
Pneumoconiosis benefit claims	97,683	72,095
Total obligations	151,067	121,634
Less current portion	(11,175)	(11,137)
Non-current obligations	$ 139,892	$ 110,497

ACCRUED WORKERS' COMPENSATION_7

ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS - Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accrued Workers Compensation And Pneumoconiosis Benefits
Workers' compensation expense	$ 17,541	$ 11,270	$ 12,215
Total expense	18,596	16,339	14,933
Pneumoconiosis benefits
Accrued Workers Compensation And Pneumoconiosis Benefits
Service cost	2,593	2,525	2,255
Interest cost	3,044	2,542	2,555
Net amortization	(4,582)	2	(2,092)
Net periodic benefit cost	$ 1,055	$ 5,069	$ 2,718

RELATED-PARTY TRANSACTIONS - Af

RELATED-PARTY TRANSACTIONS - Affiliate Royalty Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction
As of the beginning of period	$ 44,197
As of the end of period	53,901	$ 44,197
Coal lease
Related Party Transaction
As of the beginning of period	32,645	32,993	$ 19,820
Payments	15,317	10,818	16,819
Recoupment	(4,178)	(3,271)	(3,646)
Unrecoupable	(2,568)	(7,895)
As of the end of period	41,216	32,645	32,993
SGP \| Tunnel Ridge
Related Party Transaction
As of the beginning of period		3,000
Payments	4,500		6,000
Recoupment	(3,000)	(3,000)	(3,000)
As of the end of period	1,500		3,000
WKY CoalPlay \| December 2014 coal lease - Henderson and Union Counties, Kentucky
Related Party Transaction
As of the beginning of period	14,077	10,684	7,195
Payments	3,597	3,597	3,598
Recoupment	(1,071)	(204)	(109)
As of the end of period	16,603	14,077	10,684
WKY CoalPlay \| December 2014 coal lease - Webster County, Kentucky
Related Party Transaction
As of the beginning of period		5,356	3,319
Payments	2,568	2,570	2,568
Recoupment		(31)	(531)
Unrecoupable	(2,568)	(7,895)
As of the end of period			5,356
WKY CoalPlay \| December 2014 coal lease - Henderson County, Kentucky
Related Party Transaction
As of the beginning of period	10,086	7,566	5,044
Payments	2,521	2,520	2,522
As of the end of period	12,607	10,086	7,566
WKY CoalPlay \| February 2015 coal lease - Henderson and Union Counties, Kentucky
Related Party Transaction
As of the beginning of period	8,482	6,387	4,262
Payments	2,131	2,131	2,131
Recoupment	(107)	(36)	(6)
As of the end of period	$ 10,506	$ 8,482	$ 6,387

RELATED-PARTY TRANSACTIONS - _2

RELATED-PARTY TRANSACTIONS - Affiliate Royalty Agreements - SGP (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Tunnel Ridge
Related Party Transaction
Payments for earned royalties	$ 7.2	$ 6	$ 7.2
Tunnel Ridge \| Joseph W Craft III Foundation \| Tunnel Ridge
Related Party Transaction
Property ownership (as a percent)	0.50%
SGP \| Tunnel Ridge
Related Party Transaction
Annual minimum royalties	$ 3

RELATED-PARTY TRANSACTIONS - WK

RELATED-PARTY TRANSACTIONS - WKY CoalPlay and Cavalier Minerals (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2015	Dec. 31, 2014	Dec. 31, 2019	Sep. 30, 2019	Jan. 03, 2019
WKY CoalPlay \| February 2015 coal lease - Henderson and Union Counties, Kentucky
Related Party Transaction
Initial term of lease	20 years
Percentage of earned royalty on coal sale price	4.00%
Annual minimum royalties	$ 2.1
Period for option to acquire the leased reserves	3 years
Percentage of internal rate of return on purchase price, if leased reserves acquired	7.00%
WKY CoalPlay \| December 2014 coal lease - Henderson and Union Counties, Kentucky
Related Party Transaction
Initial term of lease		20 years
Percentage of earned royalty on coal sale price		4.00%
Annual minimum royalties		$ 3.6
Period for option to acquire the leased reserves		3 years
Percentage of internal rate of return on purchase price, if leased reserves acquired		7.00%
WKY CoalPlay \| December 2014 coal lease - Webster County, Kentucky
Related Party Transaction
Initial term of lease		7 years
Percentage of earned royalty on coal sale price		4.00%
Annual minimum royalties		$ 2.6
Period for option to acquire the leased reserves		3 years
Percentage of internal rate of return on purchase price, if leased reserves acquired		7.00%
Accrued payments				$ 5.1
WKY CoalPlay \| December 2014 coal lease - Henderson County, Kentucky
Related Party Transaction
Annual minimum royalties		$ 2.5
Cavalier Minerals
Related Party Transaction
Ownership interest in VIE (as a percent)			96.00%
Cavalier Minerals \| Bluegrass Minerals
Related Party Transaction
Noncontrolling ownership interest (as a percent)			4.00%		4.00%

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Purchase Commitments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Mar. 09, 2018
Contractual Commitments
Commitments to purchase coal		$ 2
Commitments for external coal purchases
Contractual Commitments
Commitments to purchase coal	$ 0
Commitments related to planned capital projects
Contractual Commitments
Contractual amount	$ 28.6

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - General Litigation (Details) - USD ($) $ in Thousands	Mar. 09, 2018	Dec. 31, 2018
Loss Contingency, Information about Litigation Matters [Abstract]
Settlement per agreement	$ 93,000
Purchase of coal reserves, agreed amount	2,000
Legal and other costs of settlement	13,000
Net gain from settlement	$ 80,000	$ 80,000

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Insurance (Details) - Property and casualty insurance $ in Millions	Oct. 01, 2019USD ($)
Commitments And Contingencies
Aggregate maximum insurance limit	$ 100
Insurance deductible	$ 1.5
Waiting period one	60 days
Waiting period two	75 days
Waiting period three	90 days
Waiting period	120 days
Overall aggregate deductible	$ 10
Percentage of participating interest in commercial property insurance program	10.00%

CONCENTRATION OF CREDIT RISK _3

CONCENTRATION OF CREDIT RISK AND MAJOR CUSTOMERS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Major Customers
Revenues	$ 1,961,720	$ 2,002,857	$ 1,796,220
Trade receivables	$ 161,679	$ 174,914
Revenue \| Geographic Concentration Risk
Major Customers
Concentration of risk (as a percent)	17.90%	27.80%	17.40%
Revenue \| Customer Concentration Risk \| Customer A
Major Customers
Revenues	$ 228,500	$ 219,115
Revenue \| Customer Concentration Risk \| Customer B
Major Customers
Revenues	213,319
Trade accounts receivable \| Customer Concentration Risk \| Major customers
Major Customers
Trade receivables	$ 26,300
Trade accounts receivable \| Customer Concentration Risk \| Customer A
Major Customers
Trade receivables		$ 12,800

SEGMENT INFORMATION - General I

SEGMENT INFORMATION - General Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019segment	Feb. 08, 2019USD ($)	Dec. 31, 2018USD ($)	Jul. 19, 2017USD ($)
Reportable segment results
Number of reportable segments	3
Number of coal reportable segments	2
Number of mining complex	7
Equity securities \| $			$ 122,094
Kodiak
Reportable segment results
Equity securities \| $		$ 0		$ 100,000

SEGMENT INFORMATION - Segment R

SEGMENT INFORMATION - Segment Results (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reportable segment results
Revenues	$ 1,961,720	$ 2,002,857	$ 1,796,220
Segment Adjusted EBITDA Expense	1,204,896	1,211,800	1,092,187
Segment Adjusted EBITDA	672,001	715,691	682,028
Total assets	2,586,694	2,394,748	2,219,371
Capital expenditures	305,858	233,480	145,088
Illinois Basin
Reportable segment results
Revenues	1,236,308	1,321,089	1,125,864
Segment Adjusted EBITDA Expense	756,423	796,370	692,199
Segment Adjusted EBITDA	385,200	417,773	398,080
Total assets	1,373,516	1,380,912	1,437,627
Capital expenditures	189,270	166,468	94,374
Appalachia
Reportable segment results
Revenues	644,389	643,965	626,041
Segment Adjusted EBITDA Expense	423,623	398,243	385,802
Segment Adjusted EBITDA	215,950	240,286	234,124
Total assets	500,027	440,518	470,892
Capital expenditures	111,739	64,037	48,358
Minerals
Reportable segment results
Revenues	53,036
Segment Adjusted EBITDA Expense	7,811
Segment Adjusted EBITDA	46,997	21,323	13,297
Total assets	643,213	161,312	147,970
Other and Corporate
Reportable segment results
Revenues	56,850	81,492	114,749
Segment Adjusted EBITDA Expense	36,845	52,321	75,851
Segment Adjusted EBITDA	32,911	44,864	45,296
Total assets	541,261	589,010	349,918
Capital expenditures	4,849	2,975	2,356
Operating segments
Reportable segment results
Revenues	1,961,720	2,002,857	1,796,220
Operating segments \| Illinois Basin
Reportable segment results
Revenues	1,219,618	1,289,898	1,069,767
Operating segments \| Appalachia
Reportable segment results
Revenues	644,389	643,898	623,720
Operating segments \| Minerals
Reportable segment results
Revenues	53,036
Operating segments \| Other and Corporate
Reportable segment results
Revenues	44,677	69,061	102,733
Elimination
Reportable segment results
Revenues	(28,863)	(43,689)	(70,434)
Segment Adjusted EBITDA Expense	(19,806)	(35,134)	(61,665)
Segment Adjusted EBITDA	(9,057)	(8,555)	(8,769)
Total assets	(471,323)	(177,004)	(187,036)
Elimination \| Illinois Basin
Reportable segment results
Revenues	16,690	31,191	56,097
Elimination \| Appalachia
Reportable segment results
Revenues		67	2,321
Elimination \| Other and Corporate
Reportable segment results
Revenues	$ 12,173	$ 12,431	$ 12,016

SEGMENT INFORMATION - EBITDA Ex

SEGMENT INFORMATION - EBITDA Expense Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of consolidated Segment Adjusted EBITDA Expense to operating expenses (excluding depreciation, depletion and amortization)
Segment Adjusted EBITDA Expense	$ 1,204,896	$ 1,211,800	$ 1,092,187
Outside coal purchases	(23,357)	(1,466)
Other expense	561	(2,621)	(332)
Operating expenses (excluding depreciation, depletion and amortization)	$ 1,182,100	$ 1,207,713	$ 1,091,855

SEGMENT INFORMATION - EBITDA Re

SEGMENT INFORMATION - EBITDA Reconciliation (Details) - USD ($) $ in Thousands	Mar. 09, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of consolidated Segment Adjusted EBITDA to net income
Consolidated Segment Adjusted EBITDA		$ 672,001	$ 715,691	$ 682,028
General and administrative		(72,997)	(68,298)	(61,760)
Depreciation, depletion and amortization		(309,075)	(280,225)	(268,981)
Settlement gain	$ 80,000		80,000
Asset impairment		(15,190)	(40,483)
Interest expense, net		(45,496)	(40,059)	(39,291)
Acquisition gain		177,043
Debt extinguishment loss				8,148
Income tax (expense) benefit		211	(22)	(210)
Acquisition gain attributable to noncontrolling interest		(7,083)
NET INCOME ATTRIBUTABLE TO ARLP		399,414	366,604	303,638
Noncontrolling interest		7,512	866	563
NET INCOME		$ 406,926	$ 367,470	$ 304,201

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation And Qualifying Accounts
Balance At Beginning of Year	$ 0	$ 0	$ 0
Additions Charged to Income	0	0	0
Deductions	0	0	0
Balance At End of Year	$ 0	$ 0	$ 0