Natural Resource Partners (NRP) 10-K 7 Mar 19 2018 Q4 Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 01, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q4
Trading Symbol	NRP
Entity Registrant Name	NATURAL RESOURCE PARTNERS LP
Entity Central Index Key	1,171,486
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		12,261,199
Entity Public Float			$ 248.4

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 101,839	$ 26,980
Restricted cash	104,191	0
Accounts receivable, net	32,024	24,050
Accounts receivable—affiliates	34	161
Prepaid expenses and other	3,462	3,782
Current assets of discontinued operations	993	36,423
Total current assets	242,543	91,396
Land	24,008	24,008
Plant and equipment, net	984	1,348
Mineral rights, net	743,112	778,419
Intangible assets, net	42,513	46,820
Equity in unconsolidated investment	247,051	245,433
Long-term contracts receivable	38,945	40,776
Long-term assets of discontinued operations	0	155,942
Other assets	2,491	4,866
Other assets—affiliate	0	156
Total assets	1,341,647	1,389,164
Current liabilities:
Accounts payable	548	1,010
Accounts payable—affiliates	1,866	490
Accrued liabilities	12,347	11,542
Accrued liabilities—affiliates	0	515
Accrued interest	14,345	15,484
Current portion of deferred revenue	3,509	0
Current portion of long-term debt, net	115,184	79,740
Current liabilities of discontinued operations	947	11,768
Total current liabilities	148,746	120,549
Deferred revenue	49,044	100,605
Long-term debt, net	557,574	729,608
Long-term liabilities of discontinued operations	0	2,220
Other non-current liabilities	1,150	588
Other non-current liabilities—affiliate	0	346
Total liabilities	756,514	953,916
Commitments and contingencies	0	0
Class A Convertible Preferred Units (250,000 and 258,844 units issued and outstanding at December 31, 2018 and 2017, respectively, at $1,000 par value per unit; liquidation preference of $1,500 per unit)	164,587	173,431
Partners’ capital:
Common unitholders’ interest (12,249,469 and 12,232,006 units issued and outstanding at December 31, 2018 and 2017, respectively)	355,113	199,851
General partner’s interest	5,014	1,857
Warrant holders’ interest	66,816	66,816
Accumulated other comprehensive loss	(3,462)	(3,313)
Total partners’ capital	423,481	265,211
Non-controlling interest	(2,935)	(3,394)
Total capital	420,546	261,817
Total liabilities and capital	$ 1,341,647	$ 1,389,164

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common Units Outstanding	12,249,469	12,232,006
Common Units Issued	12,249,469	12,232,006
Preferred Units Issued	250,000	258,844
Preferred Units Outstanding	250,000	258,844
Preferred unit purchase price	$ 1,000	$ 1,000
Temporary Equity, Liquidation Preference Per Share	$ 1,500	$ 1,500

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 251,071	$ 242,780	$ 250,176
Gain on litigation settlement	25,000	0	0
Gain on asset sales, net	2,441	3,545	29,068
Total revenues and other income	278,512	246,325	279,244
Operating expenses
Operating and maintenance expenses	17,894	16,771	20,737
Operating and maintenance expenses—affiliates	11,615	8,112	9,153
Depreciation, depletion and amortization	21,689	22,406	28,581
Amortization expense—affiliate	0	1,008	3,185
General and administrative	12,838	13,513	16,979
General and administrative—affiliates	3,658	4,989	3,591
Asset impairments	18,280	2,967	15,861
Total operating expenses	85,974	69,766	98,087
Income from operations	192,538	176,559	181,157
Other expense, net
Interest expense, net	(70,178)	(82,028)	(90,008)
Interest expense—affiliate	0	0	(523)
Debt modification expense	0	(7,939)	0
Loss on extinguishment of debt	0	(4,107)	0
Total other expense, net	(70,178)	(94,074)	(90,531)
Net income from continuing operations	122,360	82,485	90,626
Income from discontinued operations	17,687	6,182	6,266
Net income	140,047	88,667	96,892
Net income attributable to non-controlling interest	(510)	0	0
Net income attributable to NRP	139,537	88,667	96,892
Less: income attributable to preferred unitholders	(30,000)	(25,453)	0
Net income attributable to common unitholders and general partner	109,537	63,214	96,892
Net income attributable to common unitholders	107,346	61,950	95,229
Net income attributable to the general partner	$ 2,191	$ 1,264	$ 1,663
Income from continuing operations per common unit
Income from continuing operations per common unit (basic)	$ 7.35	$ 4.57	$ 7.28
Income from continuing operations per common unit (diluted)	5.90	3.68	7.28
Basic and diluted net income per common unit (in dollars per share):
Net income per common unit (basic)	8.77	5.06	7.78
Net income per common unit (diluted)	$ 6.76	$ 3.96	$ 7.78
Comprehensive income (loss) from unconsolidated investment and other	$ (149)	$ (1,647)	$ 486
Comprehensive income	139,898	87,020	97,378
Comprehensive income attributable to non-controlling interest	(510)	0	0
Comprehensive income attributable to NRP	139,388	87,020	97,378
Coal Royalty and Other
Revenues	178,394	158,399	144,520
Coal royalty and other—affiliates	484	23,402	46,259
Soda Ash
Revenues	48,306	$ 40,457	$ 40,061
Transportation and processing services | Coal Royalty and Other
Revenues	23,887
Transportation and processing services—affiliate | Coal Royalty and Other
Coal royalty and other—affiliates	$ 0

Consolidated Statements of Part

Consolidated Statements of Partners' Capital - USD ($) shares in Thousands, $ in Thousands	Total	General Partner	Common Unitholders	Warrant Holders	Accumulated Other Comprehensive Income (Loss)	Partners Capital Excluding Noncontrolling Interest	Non-Controlling Interest	Common unitholders	Common unitholdersCommon Unitholders	General Partner	General PartnerGeneral Partner	Common unitholders and general partner	Common unitholders and general partnerPartners Capital Excluding Noncontrolling Interest	Preferred Partner	Preferred PartnerGeneral Partner	Preferred PartnerCommon Unitholders	Preferred PartnerPartners Capital Excluding Noncontrolling Interest
Balance, beginning of period (in shares) at Dec. 31, 2015			12,232
Balance, beginning of period at Dec. 31, 2015	$ 72,942	$ (606)	$ 79,094	$ 0	$ (2,152)	$ 76,336	$ (3,394)
Net income (loss)	96,892	1,663	$ 95,229			96,892
Net income	96,892
Distributions to unitholders									$ (22,014)		$ (451)	$ (22,465)	$ (22,465)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Excluding General Partner Distributions	486
Comprehensive income from unconsolidated investment and other	486				486	486
Non-cash contributions	281	281				281
Balance, end of period (in shares) at Dec. 31, 2016			12,232
Balance, end of period at Dec. 31, 2016	148,136	887	$ 152,309	0	(1,666)	151,530	(3,394)
Income attributable to preferred unitholders	0
Net income (loss)	88,667	1,773	$ 86,894			88,667
Net income	88,667
Distributions to unitholders									(22,018)		(449)	(22,467)	(22,467)	$ (17,688)	$ 354	$ 17,334	$ (17,688)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Excluding General Partner Distributions	(1,647)
Issuance of Warrants	66,816			66,816		66,816
Comprehensive income from unconsolidated investment and other	(1,647)				(1,647)	(1,647)
Balance, end of period (in shares) at Dec. 31, 2017			12,232
Balance, end of period at Dec. 31, 2017	261,817	1,857	$ 199,851	66,816	(3,313)	265,211	(3,394)
Income attributable to preferred unitholders	25,453							$ (24,900)		$ (500)
Net income (loss)	139,537					139,537
Net income	140,047	2,791	$ 136,746				510
Distributions to unitholders									$ (22,036)		$ (450)	$ (22,486)	$ (22,486)	$ (30,265)	$ (605)	$ (29,660)	$ (30,265)
Partners' Capital Account, Units, Unit-based Compensation			17
Partners' Capital Account, Unit-based Compensation	546		$ 546			546
Partners' Capital Account, Unit-based Compensation, Amortization	560		560			560
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent, Excluding General Partner Distributions	(149)	12	$ 49		(149)		(51)
Comprehensive income from unconsolidated investment and other	(139)					(88)
Balance, end of period (in shares) at Dec. 31, 2018			12,249
Balance, end of period at Dec. 31, 2018	420,546	$ 5,014	$ 355,113	$ 66,816	$ (3,462)	$ 423,481	$ (2,935)
Income attributable to preferred unitholders	$ 30,000							$ (29,400)		$ (600)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations	$ 206,030	$ 29,827	$ 40,371
Net income	140,047	88,667	96,892
Adjustments to reconcile net income to net cash provided by operating activities of continuing operations:
Depreciation, depletion and amortization	21,689	22,406	28,581
Amortization expense—affiliate	0	1,008	3,185
Distributions from unconsolidated investment	44,453	43,354	46,550
Equity earnings from unconsolidated investment	(48,306)	(40,457)	(40,061)
Gain on asset sales, net	(2,441)	(3,545)	(29,068)
Debt modification expense	0	7,939	0
Loss on extinguishment of debt	0	4,107	0
Income from discontinued operations	(17,687)	(6,182)	(6,266)
Asset impairments	18,280	2,967	15,861
Unit-based compensation expense	1,434	18	1,217
Amortization of debt issuance costs and other	7,334	9,077	8,638
Other—affiliates	(201)	1,207	993
Change in operating assets and liabilities:
Accounts receivable	(6,251)	5,905	1,545
Accounts receivable—affiliates	127	367	(313)
Accounts payable	(238)	(185)	517
Accounts payable—affiliates	1,376	1	0
Accrued liabilities	134	(8,478)	3,628
Accrued liabilities—affiliates	(115)	515	0
Accrued interest	(1,138)	(105)	(779)
Accrued interest—affiliates	0	0	(456)
Deferred revenue	19,465	(5,791)	(35,881)
Deferred revenue—affiliates	0	(10,166)	(12,063)
Other items, net	320	(478)	(2,477)
Net cash provided by operating activities of continuing operations	178,282	112,151	80,243
Net cash provided by operating activities of discontinued operations	10,641	14,988	27,718
Net cash provided by operating activities	188,923	127,139	107,961
Cash flows from investing activities
Distributions from unconsolidated investment in excess of cumulative earnings	2,097	5,646	0
Proceeds from sale of assets	2,449	1,151	62,117
Return of long-term contract receivable	3,061	2,206	0
Return of long-term contract receivable—affiliate	0	804	2,968
Acquisition of plant and equipment and other	0	0	(28)
Net cash provided by investing activities of continuing operations	7,607	9,807	65,057
Net cash provided by (used in) investing activities of discontinued operations	183,021	(6,264)	101,758
Net cash provided by investing activities	190,628	3,543	166,815
Cash flows from financing activities
Proceeds from issuance of preferred units and warrants, net	0	242,100	0
Proceeds from issuance of 2022 Senior Notes, net	0	103,688	0
Borrowings on credit facility	35,000	77,000	20,000
Repayments of loans	(175,706)	(492,319)	(183,141)
Contributions from discontinued operations	195,690	5,784	52,642
Debt issuance costs and other	(228)	(39,091)	(13,409)
Net cash used in financing activities of continuing operations	(6,839)	(134,149)	(146,373)
Net cash used in financing activities of discontinued operations	(196,509)	(7,077)	(139,805)
Net cash used in financing activities	(203,348)	(141,226)	(286,178)
Net increase (decrease) in cash, cash equivalents and restricted cash	176,203		(11,402)
Cash, cash equivalents and restricted cash of discontinued operations at beginning of period	0	2,847	1,200
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	206,030	26,980	39,171
Cash paid during the period for interest from continuing operations	64,991	72,850	84,380
Issuance of 2022 Senior Notes in exchange for 2018 Senior Notes	0	240,638	0
Preferred Partner
Cash flows from financing activities
Distributions to common unitholders and general partner	(30,265)	(8,844)	0
General Partner
Cash flows from financing activities
Distributions to common unitholders and general partner	(22,486)	(22,467)	(22,465)
Class A Convertible Preferred Units
Cash flows from financing activities
Dividends, Preferred Stock, Paid-in-Kind, Cash Redemption Payment	$ (8,844)	$ 0	$ 0

Organization and Nature of Oper

Organization and Nature of Operations	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Nature of Operations	Organization and Nature of Operations Natural Resource Partners L.P. (the "Partnership"), a Delaware limited partnership, was formed in April 2002. The general partner of the Partnership is NRP (GP) LP ("NRP GP"), a Delaware limited partnership, whose general partner is GP Natural Resource Partners LLC, a Delaware limited liability company. The Partnership engages principally in the business of owning, managing and leasing a diversified portfolio of mineral properties in the United States, including interests in coal, trona, soda ash and other natural resources and is organized into two operating segments further described in Note 8. Segment Information. As used in these Notes to Consolidated Financial Statements, the terms "NRP," "we," "us" and "our" refer to Natural Resource Partners L.P. and its subsidiaries, unless otherwise stated or indicated by context. The Partnership’s operations are conducted through, and its operating assets are owned by, its subsidiaries. The Partnership owns its subsidiaries through one wholly owned operating company, NRP (Operating) LLC ("Opco"). NRP GP has sole responsibility for conducting the Partnership's business and for managing its operations. Because NRP GP is a limited partnership, its general partner, GP Natural Resource Partners LLC, conducts its business and operations, and the board of directors and officers of GP Natural Resource Partners LLC makes decisions on its behalf. Robertson Coal Management LLC ("RCM"), a limited liability company wholly owned by Corbin J. Robertson, Jr., owns all of the membership interest in GP Natural Resource Partners LLC. Subject to the Board Representation and Observation Rights Agreement with certain entities controlled by funds affiliated with The Blackstone Group, L.P. (collectively referred to as "Blackstone") and affiliates of GoldenTree Asset Management LP (collectively referred to as "GoldenTree"), RCM is entitled to appoint the directors of the Board of Directors of GP Natural Resource Partners LLC. RCM has delegated the right to appoint one director to Blackstone.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying Consolidated Financial Statements of the Partnership have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP"). The consolidated financial statements include the accounts of Natural Resource Partners L.P. and its wholly owned subsidiaries, as well as BRP LLC ("BRP"), a joint venture with International Paper Company controlled by the Partnership. The Partnership has an equity investment in Ciner Wyoming through which it is able to exercise significant influence over but does not control the investee and is not the primary beneficiary of the investee’s activities and is accounted for using the equity method. Intercompany transactions and balances have been eliminated. Certain reclassifications have been made to prior year amounts on the Consolidated Statements of Comprehensive Income and Consolidated Statements of Cash Flows to conform with current year presentation. These reclassifications have no impact on previously reported net income or total cash flows from operating, investing or financing activities. Recasting of Certain Prior Period Information As described in Note 4. Discontinued Operations , the Partnership has classified the assets and liabilities, operating results and cash flows of its construction aggregates business as discontinued operations in its consolidated financial statements for all periods presented. Use of Estimates Preparation of the accompanying financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities in the accompanying Consolidated Balance Sheets, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses in the accompanying Consolidated Statements of Comprehensive Income during the reporting period. Actual results could differ from those estimates. The most significant estimates pertain to coal and aggregates reserves and related cash flow estimates which are used to compute depreciation, depletion and amortization and impairments of coal and aggregates properties and commitments and contingencies. Fair Value The Partnership discloses certain assets and liabilities using fair value as defined by authoritative guidance. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. See Note 14. Fair Value Measurements for further details. There are three levels of inputs that may be used to measure fair value: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial assets and liabilities whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. Cash, Cash Equivalents and Restricted Cash The Partnership considers all highly liquid short-term investments with an original maturity of three months or less to be cash equivalents. Restricted cash at December 31, 2018 included cash proceeds received from the sale of the Partnership's construction aggregates business required to be used to repay debt, make acquisitions or make capital expenditures per the terms of its and Opco's debt agreements, as defined in Note 13. Debt, Net . NRP intends to use these proceeds to repay debt. Allowance for Doubtful Accounts The Partnership records an allowance for doubtful accounts for its accounts receivables and notes receivables which it determines to be uncollectible based on the specific identification method. Receivables are written off when collection efforts are exhausted and future recovery is doubtful. The allowance for doubtful accounts receivable is included in Accounts receivable, net and the allowance for doubtful accounts for notes receivable is included in Other current assets on the Partnership's Consolidated Balance Sheets, respectively. The allowance for doubtful accounts related to accounts receivable was $4.8 million at December 31, 2017 . The allowance for doubtful accounts related to notes receivable included in Other current assets was $1.2 million at both December 31, 2018 and 2017, respectively. The Partnership recorded bad debt expense of $0.1 million , $2.4 million and $0.3 million , respectively, included in Operating and maintenance expense (including affiliates) on its Consolidated Statements of Comprehensive Income for the years ended December 31, 2018, 2017 and 2016, respectively. Plant and Equipment Plant and equipment is recorded at its original cost of construction or, upon acquisition, at fair value of the asset acquired and consists of coal preparation plants, related coal handling facilities, and other coal and aggregates transportation and processing infrastructure. Expenditures for new facilities or that substantially increase the useful life of property are capitalized and reported in the Consolidated Statements of Cash Flows as an investing activity. These assets are depreciated on a straight-line basis over their useful lives generally as follows: Years Buildings and improvements 20 to 40 Machinery and equipment 5 to 12 Leasehold improvements Life of Lease Mineral Rights Mineral rights owned and leased are recorded at its original cost of construction or, upon acquisition, at fair value of the assets acquired. Coal and aggregates mineral rights are depleted on a unit-of-production basis by lease, based upon minerals mined in relation to the net cost of the mineral properties and estimated proven and probable tonnage therein. Intangible Assets The Partnership’s intangible assets consist primarily of contracts that at acquisition were more favorable for the Partnership than prevailing market rates, known as above-market contracts. Management expects for the above-market rates to be received until the reserves are exhausted on its above-market contracts, which includes additional renewal terms of the respective leases. The estimated fair values of the above-market rate contracts are determined based on the present value of future cash flow projections related to the underlying assets acquired. Intangible assets are amortized on a unit-of-production basis. Asset Impairment The Partnership has developed procedures to evaluate its long-lived assets for possible impairment periodically or whenever events or changes in circumstances indicate an asset's carrying amount may not be recoverable. Potential events or circumstances include, but are not limited to, specific events such as a reduction in economically recoverable reserves or production ceasing on a property for an extended period. This analysis is based on historic, current and future performance and considers both quantitative and qualitative information. A long-lived asset is deemed impaired when the future expected undiscounted cash flows from its use and disposition is less than the assets’ carrying value. Impairment is measured based on the estimated fair value, which is usually determined based upon the present value of the projected future cash flow compared to the assets’ carrying value. The Partnership believes its estimates of cash flows and discount rates are consistent with those of principal market participants. The Partnership evaluates its equity investment for impairment when events or changes in circumstances indicate, in management’s judgment, that the carrying value of such investment may have experienced an other-than-temporary decline in value. When evidence of loss in value has occurred, management compares the estimated fair value of the investment to the carrying value of the investment to determine whether potential impairment has occurred. If the estimated fair value is less than the carrying value and management considers the decline in value to be other than temporary, the excess of the carrying value over the estimated fair value is recognized in the financial statements as an impairment loss. The fair value of the impaired investment is based on quoted market prices (Level 1), or upon the present value of expected cash flows using discount rates believed to be consistent with those used by principal market participants (Level 3), plus market analysis of comparable assets owned by the investee, if appropriate. Revenue Recognition Coal Royalty and Other Segment Revenues Royalty-based leases. Approximately two-thirds of the Partnership's royalty-based leases have initial terms of five to 40 years, with substantially all lessees having the option to extend the lease for additional terms. For these types of leases, the lessees generally make payments to NRP based on the greater of a percentage of the gross sales price or a fixed price per ton of mineral they mine or sell. Most of NRP’s coal and aggregates royalty leases require the lessee to pay quarterly or annual minimum amounts, either made in advance or arrears, which are generally recoupable through actual royalty production over certain time periods that generally range from three to five years. In accordance with previous accounting standards in effect prior to January 1, 2018, NRP recognized all coal and aggregates royalty revenue over the lease term based on production. The recognition of revenue from minimum payments was deferred until either recoupment through royalty production occurred or when the recoupment period expired for unrecouped minimums. Under the new revenue recognition standard, management has defined NRP's coal and aggregates royalty lease performance obligation as providing the lessee the right to mine and sell NRP's coal or aggregates over the lease term. The Partnership then evaluated the likelihood that consideration NRP expected to receive from its lessees resulting from production would exceed consideration expected to be received from minimum payments over the lease term. As a result of this evaluation, revenue recognition from the Partnership's royalty-based leases is based on either production or minimum payments as follows: • Production Leases : Leases for which the Partnership expects that consideration from production will be greater than consideration from minimums over the lease term. Revenue recognition for these leases is recognized over time based on production as Coal royalty revenue or Aggregates royalty revenue, as applicable. Deferred revenue from minimums is recognized as royalty revenue when recoupment occurs or as Production lease minimum revenue when the recoupment period expires. In addition, NRP recognizes breakage revenue from minimums when NRP determines that recoupment is remote. This breakage revenue is included in Production lease minimum revenue. • Minimum Leases : Leases for which the Partnership expects that consideration from minimums will be greater than consideration from production over the lease term. Revenue recognition for these leases is recognized straight-line over the lease term based on the minimum consideration amount as Minimum lease straight-line revenue. This evaluation is performed at the inception of the lease and only reassessed upon modification or renewal of the lease. Oil and gas related revenues consist of revenues from royalties and overriding royalties and are recognized on the basis of volume of hydrocarbons sold by lessees and the corresponding revenue from those sales. Also, included within oil and gas royalties are lease bonus payments, which are generally paid upon the execution of a lease. The Partnership also has overriding royalty revenue interests in coal reserves. Revenue from these interests is recognized over time based on when the coal is sold. Wheelage. Revenue related to fees collected per ton to transport foreign coal across property owned by the Partnership that is recognized over time as transportation across the property occurs. Other revenue. Other revenue consists primarily of rental payments and surface damage fees related to certain land owned by the Partnership and is recognized straight-line over time as it is earned. Other revenues also include property tax revenues. The majority of property taxes paid on the Partnership's properties are reimbursable by the lessee and are recognized on a gross basis over time which reflects the reimbursement of property taxes by the lessee. Property taxes paid by NRP are included in Operating and maintenance expenses on the Partnership's Consolidated Statements of Comprehensive Income. Transportation and processing services revenue. The Partnership owns transportation and processing infrastructure that is leased to third parties for throughput fees. Revenue is recognized over time based on the coal tons transported over the beltlines or processed through the facilities. Contract modifications Contract modifications that impact goods or services or the transaction price are evaluated in accordance with ASC 606. A majority of the Partnership's contract modifications pertain to its coal and aggregates royalty contracts and include, but are not limited to, extending the lease term, changes to royalty rates, floor prices or minimum consideration, assignment of the contract, forfeiture of recoupment rights or termination due to the exhaustion of merchantable and mineable reserves. Consideration received in conjunction with a modification of an ongoing lease will be deferred and recognized straight-line over the remaining term of the contract. Consideration received to assign a lease to another party and related forfeited minimums will be recognized immediately upon the termination of the contract. Fees from contract modifications are recognized in Lease modification fees within Coal royalty and other revenues on our Consolidated Statements of Comprehensive Income while modifications in royalty rates and minimums will be recognized prospectively in accordance with the above lease classification. In accordance with the transition guidance in paragraph 606-10-65-1, revenues from contracts that were modified before January 1, 2018 were not retrospectively restated for those modifications and instead reflected the aggregate effect of those modifications when identifying the satisfied and unsatisfied performance obligations, determining the transaction price and allocating the transaction price to the satisfied and unsatisfied performance obligation. Contract Assets and Liabilities from Contracts with Customers Contract assets include receivables from contracts with customers and are recorded when the right to consideration becomes unconditional. Receivables are recognized when the minimums are contractually owed, production occurs or minimums accrued for based on the passage of time. Contract liabilities represent minimum consideration received, contractually owed or earned based on the passage of time. The current portion of deferred revenue relates to deferred revenue on minimum leases and lease modification fees that are to be recognized as revenue on a straight-line basis over the next twelve months. The long-term portion of deferred revenue relates to deferred revenue on production leases and lease modification fees that are to be recognized as revenue on a straight-line basis beyond the next twelve months. Due to uncertainty in the amount of deferred revenue that will be recouped and recognized as Coal royalty revenue from its production leases over the next twelve months, the Partnership is unable to estimate the current portion of deferred revenue. See "—Recently Adopted Accounting Standards—Revenue Recognition" below for information regarding the impact of adopting the new revenue recognition standard in January 2018. Equity in Earnings from Ciner Wyoming The Partnership accounts for non-marketable equity investments using the equity method of accounting if the investment gives it the ability to exercise significant influence over, but not control of, an investee. The Partnership's 49% investment in Ciner Wyoming is accounted for using this method. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and the proportionate share of earnings or losses and distributions. The basis difference between the investment and the proportional share of investee's net assets is attributed to net tangible assets and is amortized over its estimated useful life. The carrying value in Ciner Wyoming is recognized in Equity in unconsolidated investment in the Partnership's Consolidated Balance Sheets. The Partnership's adjusted share of the earnings or losses of Ciner Wyoming and amortization of the basis difference is recognized in Equity in earnings of Ciner Wyoming in the Consolidated Statements of Comprehensive Income. The Partnership increases its investment for its proportional share of distributions received from Ciner Wyoming. These cash flows are reported utilizing the cumulative earnings approach. Under this approach, distributions received are considered returns on investment and classified as operating cash inflows unless the cumulative distributions received exceed the Partnership's cumulative equity in earnings. The excess of cumulative distributions received over the Partnership's cumulative equity in earnings are considered returns of investment and classified as investing cash inflows. Property Taxes The Partnership is responsible for paying property taxes on the properties it owns. Typically, the lessees are contractually responsible for reimbursing the Partnership for property taxes on the leased properties. The payment of and reimbursement of property taxes is included in Operating and maintenance expenses and in Coal royalty and other revenues, respectively, in the Consolidated Statements of Comprehensive Income. Transportation Revenue and Expense The Partnership records transportation revenue and pays transportation costs to a Foresight Energy LP ("Foresight Energy") affiliate to operate equipment on behalf of the Partnership. The revenue and expenses related to these transactions are recorded as Transportation and processing services (or Transportation and processing services—affiliates) and Operating and maintenance expenses or (Operating and maintenance expenses—affiliates), respectively, in the Consolidated Statements of Comprehensive Income. Subsequent to May 9, 2017, Foresight Energy is no longer deemed a related party. Refer to Note 15. Related Party Transactions for further details. Unit-Based Compensation The Partnership has awarded unit-based compensation in the form of equity-based awards and phantom units. Compensation cost is measured at the grant date for equity-classified awards and remeasured each reporting period for liability-classified awards based on the fair value of an award and is recognized over the service period, which is generally the vesting period. Forfeitures are recognized as they occur. Unit-based compensation expense for all awards is recognized in General and administrative expense and Operating and maintenance expense in the Consolidated Statements of Comprehensive Income. Deferred Financing Costs Deferred financing costs consist of legal and other costs related to the issuance of the Partnership’s debt. These costs are amortized over the term of the respective line-of-credit or debt arrangements. Deferred financing costs related to the Partnership's revolving credit facility are included in Other assets (long-term) on the Partnership's Consolidated Balance Sheets. Deferred financing costs related to the Partnership's note agreements are included as a direct deduction from the carrying amount of the debt liability in Current portion of long-term debt, net or Long-term debt, net on the Partnership's Consolidated Balance Sheets. Income Taxes The Partnership is not subject to federal or material state income taxes, as the unitholders are taxed individually on their allocable share of taxable income. Net income for financial statement purposes may differ significantly from taxable income reportable to unitholders as a result of differences between the tax basis and financial reporting basis of assets and liabilities. In the event of an examination of the Partnership’s tax return, the tax liability of the unitholders could be changed if an adjustment in the Partnership’s income is ultimately sustained by the taxing authorities. Recently Adopted Accounting Standards Revenue Recognition On January 1, 2018, NRP adopted Accounting Standards Codification (ASC) 606, Revenue from Contracts with Customers, and all the related amendments (the “new revenue standard” and "ASC 606") to all open contracts using the modified retrospective method. The adoption of the new revenue standard impacted royalty revenue from NRP's coal and aggregates royalty leases as further described below. NRP recognized a $70.5 million cumulative effect of adoption adjustment in the opening balance of partners' capital on January 1, 2018. Prior year information has not been restated and continues to be reported under the accounting standards in effect for those periods. The new revenue standard had no impact on revenues from NRP's Soda Ash operating segment or on the discontinued operations. A majority of NRP’s coal and aggregates royalty revenue continues to be recognized over the lease term based on production. For coal and aggregates royalty leases for which NRP expects consideration from minimum payments to be greater than consideration from production over the lease term, royalty revenue is now recognized straight-line over the lease term based on the minimum payment consideration. The cumulative effects of the changes made to the Partnership's Consolidated Balance Sheet at January 1, 2018 for the adoption of the new revenue standard were as follows: (In thousands) Balance at December 31, 2017 Adjustments due to ASC 606 Balance at January 1, 2018 Assets Accounts receivable, net (including affiliates) $ 24,211 $ 4,875 $ 29,086 Liabilities Current portion of deferred revenue $ — $ 1,022 $ 1,022 Deferred revenue 100,605 (66,613 ) 33,992 Partners’ capital Common unitholders’ interest $ 199,851 $ 69,057 $ 268,908 General partner’s interest 1,857 1,409 3,266 Total partners’ capital 265,211 70,466 335,677 The impact of adoption of the new revenue standard on NRP’s Consolidated Balance Sheet and Consolidated Statement of Comprehensive Income was as follows: As of December 31, 2018 (In thousands) As Reported Balances without Adoption of ASC 606 Effect of Change Assets Accounts receivable, net (including affiliates) $ 32,058 $ 27,520 $ 4,538 Total assets 1,341,647 1,337,109 4,538 Liabilities and capital Current portion of deferred revenue $ 3,509 $ — $ 3,509 Deferred revenue 49,044 62,783 (13,739 ) Total liabilities 756,514 766,744 (10,230 ) Partners’ capital Common unitholders’ interest $ 355,113 $ 340,640 $ 14,473 General partner’s interest 5,014 4,719 295 Total partners’ capital 423,481 408,713 14,768 Total liabilities and capital 1,341,647 1,337,109 4,538 For the Year Ended December 31, 2018 (In thousands, except per unit data) As Reported Amounts without Adoption of ASC 606 Effect of Change Coal royalty and other revenues (including affiliates) (1) $ 178,878 $ 234,428 $ (55,550 ) Net income from continuing operations 122,360 178,058 (55,698 ) Net income 140,047 195,745 (55,698 ) Net income per common unit (basic) 8.77 13.23 (4.46 ) Net income per common unit (diluted) 6.76 9.46 (2.70 ) (1) The total effect of adopting ASC 606 was $55.6 million during the year ended December 31, 2018, which included $33.4 million related to the forfeiture of recoupable balances in connection with the fourth quarter 2018 settlement of the Macoupin and Hillsboro lawsuits, the majority of which was previously recognized in partners' capital upon adoption and $7.2 million of modification fees and forfeited recoupable balances related to fourth quarter 2018 lease modifications which were deferred under ASC 606 and will be recognized straight-line over the respective modified lease terms. Recently Issued Accounting Standards Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The new standard requires a lessee to recognize assets and liabilities on the balance sheet for the present value of the rights and obligations created by all leases with terms of more than 12 months. This standard does not apply to leases that explore for or use minerals, oil, natural gas and similar non-regenerative resources, including the intangible right to explore for those natural resources and rights to use the land in which those natural resources are contained. The guidance also requires disclosures designed to give financial statement users information on the amount, timing and uncertainty of cash flows arising from leases. The guidance is effective for annual and interim periods beginning after December 15, 2018 and is to be adopted using a modified retrospective approach. The Partnership will adopt this standard effective January 1, 2019 and does not expect that the provisions of this guidance will have a material impact on its consolidated financial statements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	3. Revenue from Contracts with Customers Coal Royalty and Other Segment The following table represents the Partnership's Coal Royalty and Other segment revenues (including affiliates) by major source: Year Ended (In thousands) December 31, 2018 Coal royalty revenue $ 129,341 Production lease minimum revenue 8,207 Minimum lease straight-line revenue 2,362 Property tax revenue 5,422 Wheelage revenue 6,484 Coal overriding royalty revenue 13,878 Aggregates royalty revenue 4,739 Oil and gas royalty revenue 6,608 Other revenue 1,837 Coal royalty and other revenues (1) $ 178,878 Transportation and processing services revenue (2) 23,887 Total Coal royalty and other segment revenues $ 202,765 (1) Represents revenue from contracts with customers as defined under ASC 606. (2) Revenue from contracts with customers as defined under ASC 606 was $13.2 million for the year ended December 31, 2018 . The remaining transportation and processing services revenue of $10.7 million for the year ended December 31, 2018 was related to other NRP-owned infrastructure leased to and operated by third party operators accounted for under ASC 840, Leases. See Note 15. Related Party Transactions for more information on the transportation and processing services. Contract Assets and Liabilities The following table details the Partnership's Coal Royalty and Other segment receivables and liabilities resulting from contracts with customers: December 31, January 1, (In thousands) 2018 2018 Receivables Total accounts receivable, net (including affiliates) (1) $ 29,001 $ 25,443 Prepaid expenses and other (2) 2,483 2,830 Contract liabilities Current portion of deferred revenue $ 3,509 $ 1,022 Deferred revenue 49,044 33,992 (1) Included in this amount is $4.4 million and $ 1.9 million of accounts receivable related to accrued minimum consideration as of December 31, 2018 and January 1, 2018, respectively. (2) Notes receivable from contracts with customers are included within Prepaid expenses and other in the Consolidated Balance Sheets. The following table shows the activity related to the Partnership's Coal Royalty and Other segment deferred revenue: Year Ended (In thousands) December 31, 2018 Balance at December 31, 2017 $ 100,605 Cumulative adjustment for change in accounting principle (1) (65,591 ) Balance at January 1, 2018 (current and non-current) $ 35,014 Recognition of previously deferred revenue (20,242 ) Accrued minimum payments and lease modification fees due 5,592 Cash received for minimum payments and lease modification fees 32,189 Balance at December 31, 2018 (current and non-current) (2) $ 52,553 (1) Included in this amount is $(67.5) million recognized in Partners' capital and $1.9 million of accrued minimum consideration recognized in Accounts receivable, net. (2) Included in this amount is $7.2 million of deferred modification fees and forfeited recoupable balances which will be recognized straight-line over the respective modified lease terms in Coal Royalty and other revenues on the Consolidated Statements of Comprehensive Income over the remaining terms of the modified leases, which extend over the next 6 years . The following table shows the Partnership's Coal Royalty and Other segment revenue recognized during the year ended December 31, 2018 that was included in the deferred revenue balance at the beginning of the period: Year Ended (In thousands) December 31, 2018 Production leases - revenue impact Recoupments recognized in Coal and aggregates royalty revenue $ 10,178 Breakage revenue recognized in Production lease minimum revenue 7,169 Expiration of unrecouped minimums recognized in Production lease minimum revenue 935 Minimum leases - revenue impact Minimum lease amortization recognized in Minimum lease straight-line revenue 1,960 Total previously deferred revenue recognized $ 20,242 Remaining Performance Obligations The Partnership's non-cancelable annual minimum payments due under the lease terms of its coal and aggregates royalty leases are as follows: Lease Term (1) Weighted Average Remaining Years as of December 31, 2018 Annual Minimum Payments (In thousands) 1 - 5 years 0.6 $ 13,072 5 - 10 years 1.3 13,060 10+ years 9.0 41,202 (1) The Partnership applied the practical expedient for disclosing remaining performance obligations for contracts with an expected duration of one year or less, and have excluded those contracts from this disclosure. The Partnership's non-cancelable annual minimum payments on its coal and aggregates royalty leases are recognized as revenue as discussed above. In addition, the Partnership's non-cancelable annual minimum payments due under terms of its coal and aggregates overriding royalty agreements include a $1.8 million annual minimum that expires in 2023 and a $1.0 million minimum that expires upon exhaustion of the mineable and recoverable coal reserves, respectively.

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations	Discontinued Operations In December 2018, the Partnership sold VantaCore Partners LLC, its construction aggregates materials business for $205 million , before customary purchase price adjustments and transaction expenses, and recorded a gain of $13.1 million . The Partnership's debt agreements require that 75% of the asset sale proceeds be used to pay down the Opco Revolving Credit Facility (as defined in Note 13. Debt, Net ) and 25% be offered to the holders of its Opco Senior Notes (as defined in Note 13. Debt, Net ) on a pro-rata basis. The outstanding balance was repaid on the Opco Revolving Credit Facility in December 2018, $49 million was offered to the holders of the Opco Senior Notes in December 2018 and paid in January 2019 and the remaining $55 million of net cash proceeds was restricted as of December 31, 2018. NRP intends to use these remaining proceeds to repay its Opco Senior Notes as they amortize in 2019. In July 2016, NRP Oil and Gas LLC ("NRP Oil and Gas") sold its non-operated oil and gas working interest assets for $116.1 million in gross sales proceeds. The sale had an effective date of April 1, 2016. The Partnership's exit from both its construction aggregates materials business and non-operated oil and gas working interest business represented strategic shifts to reduce debt and focus on its Coal Royalty and Other and Soda Ash business segments. As a result, the Partnership classified the assets and liabilities, operating results and cash flows of these businesses as discontinued operations in its Consolidated Balance Sheets, Consolidated Statements of Comprehensive Income and Consolidated Statements of Cash Flows for all periods presented. The following tables present the carrying amounts of the Partnership's assets and liabilities of discontinued operations in the Consolidated Balance Sheets: December 31, 2018 (In thousands) Construction Aggregates NRP Total ASSETS Current assets: Accounts receivable, net $ 5 $ 988 $ 993 Total assets of discontinued operations $ 5 $ 988 $ 993 LIABILITIES Current liabilities: Accounts payable (including affiliates) $ 181 $ — $ 181 Accrued liabilities 766 — 766 Total liabilities of discontinued operations $ 947 $ — $ 947 December 31, 2017 (In thousands) Construction Aggregates NRP Total ASSETS Current assets: Cash and cash equivalents $ 2,847 $ — $ 2,847 Accounts receivable, net 22,976 991 23,967 Inventory 7,553 — 7,553 Prepaid expenses and other 2,056 — 2,056 Total current assets of discontinued operations 35,432 991 36,423 Land 1,239 — 1,239 Plant and equipment, net 44,822 — 44,822 Mineral rights, net 105,466 — 105,466 Intangible assets, net 2,734 — 2,734 Other assets 1,681 — 1,681 Total assets of discontinued operations $ 191,374 $ 991 $ 192,365 LIABILITIES Current liabilities: Accounts payable (including affiliates) (1) $ 6,019 $ — $ 6,019 Accrued liabilities 5,348 — 5,348 Other — 401 401 Total current liabilities of discontinued operations 11,367 401 11,768 Other non-current liabilities 2,220 — 2,220 Total liabilities of discontinued operations $ 13,587 $ 401 $ 13,988 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party liabilities. The following tables present summarized financial results of the Partnership's discontinued operations in the Consolidated Statements of Comprehensive Income: For the Year Ended December 31, 2018 (In thousands) Construction Aggregates NRP Oil and Gas Total Revenues and other income: Construction aggregates $ 116,066 $ — $ 116,066 Road construction and asphalt paving services 18,400 — 18,400 Oil and gas — (3 ) (3 ) Gain on asset sales, net 13,414 — 13,414 Total revenues and other income $ 147,880 $ (3 ) $ 147,877 Operating expenses: Operating and maintenance expenses (including affiliates) (1) $ 117,568 $ 134 $ 117,702 Depreciation, depletion and amortization 12,218 — 12,218 Asset impairments 232 — 232 Total operating expenses $ 130,018 $ 134 $ 130,152 Interest expense, net (38 ) — (38 ) Income (loss) from discontinued operations $ 17,824 $ (137 ) $ 17,687 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party expenses. For the Year Ended December 31, 2017 (In thousands) Construction Aggregates NRP Oil and Gas Total Revenues and other income: Construction aggregates $ 112,970 $ — $ 112,970 Road construction and asphalt paving services 18,411 — 18,411 Oil and gas — 38 38 Gain (loss) on asset sales 311 (289 ) 22 Total revenues and other income $ 131,692 $ (251 ) $ 131,441 Operating expenses: Operating and maintenance expenses (including affiliates) (1) $ 111,633 $ 290 $ 111,923 Depreciation, depletion and amortization 12,579 — 12,579 Asset impairments 64 — 64 Total operating expenses $ 124,276 $ 290 $ 124,566 Interest expense, net (693 ) — (693 ) Income (loss) from discontinued operations $ 6,723 $ (541 ) $ 6,182 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party expenses. For the Year Ended December 31, 2016 (In thousands) Construction Aggregates NRP Oil and Gas Total Revenues and other income: Construction aggregates $ 103,755 $ — $ 103,755 Road construction and asphalt paving services 17,047 — 17,047 Oil and gas — 16,486 16,486 Gain on asset sales, net 13 8,274 8,287 Total revenues and other income $ 120,815 $ 24,760 $ 145,575 Operating expenses: Operating and maintenance expenses (including affiliates) (1) $ 100,656 $ 11,503 $ 112,159 Depreciation, depletion and amortization 14,506 7,527 22,033 Asset impairments 1,065 564 1,629 Total operating expenses $ 116,227 $ 19,594 $ 135,821 Interest expense, net — (3,488 ) (3,488 ) Income from discontinued operations $ 4,588 $ 1,678 $ 6,266 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party expenses. The following table presents supplemental cash flow information of the Partnership's discontinued operations: Year Ended December 31, (In thousands) 2018 2017 2016 Cash paid for interest $ — $ — $ 1,906 Plant, equipment and mineral rights funded with accounts payable or accrued liabilities 881 294 — Capital expenditures related to the Partnership's discontinued operations were $10.9 million , $7.6 million and $6.7 million during the years ended December 31, 2018, 2017 and 2016, respectively.

Class A Convertible Preferred U

Class A Convertible Preferred Units and Warrants	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Class A Convertible Preferred Units and Warrants	Class A Convertible Preferred Units and Warrants On March 2, 2017, NRP issued $250 million of Class A Convertible Preferred Units representing limited partner interests in NRP (the "Preferred Units") to certain entities controlled by funds affiliated with The Blackstone Group, L.P. (collectively referred to as "Blackstone") and certain affiliates of GoldenTree Asset Management LP (collectively referred to as "GoldenTree") (together the "Preferred Purchasers") pursuant to a Preferred Unit and Warrant Purchase Agreement. NRP issued 250,000 Preferred Units to the Preferred Purchasers at a price of $1,000 per Preferred Unit (the "Per Unit Purchase Price"), less a 2.5% structuring and origination fee. The Preferred Units entitle the Preferred Purchasers to receive cumulative distributions at a rate of 12% per year, up to one half of which NRP may pay in additional Preferred Units (such additional Preferred Units, the "PIK Units"). The Preferred Units have a perpetual term, unless converted or redeemed as described below. NRP also issued two tranches of warrants (the "Warrants") to purchase common units to the Preferred Purchasers (Warrants to purchase 1.75 million common units with a strike price of $22.81 and Warrants to purchase 2.25 million common units with a strike price of $34.00 ). The Warrants may be exercised by the holders thereof at any time before the eighth anniversary of the closing date. Upon exercise of the Warrants, NRP may, at its option, elect to settle the Warrants in common units or cash, each on a net basis. After March 2, 2022 and prior to March 2, 2025, the holders of the Preferred Units may elect to convert up to 33% of the outstanding Preferred Units in any 12-month period into common units if the volume weighted average trading price of our common units (the "VWAP") for the 30 trading days immediately prior to date notice is provided is greater than $51.00 . In such case, the number of common units to be issued upon conversion would be equal to the Per Unit Purchase Price plus the value of any accrued and unpaid distributions divided by an amount equal to a 7.5% discount to the VWAP for the 30 trading days immediately prior to the notice of conversion. Rather than have the Preferred Units convert to common units in accordance with the provisions of this paragraph, NRP would have the option to elect to redeem the Preferred Units proposed to be converted for cash at a price equal to Per Unit Purchase Price plus the value of any accrued and unpaid distributions. On or after March 2, 2025, the holders of the Preferred Units may elect to convert the Preferred Units to common units at a conversion rate equal to the Liquidation Value divided by an amount equal to a 10% discount to the VWAP for the 30 trading days immediately prior to the notice of conversion. The “Liquidation Value” will be an amount equal to the greater of: (1) (a) the Per Unit Purchase Price multiplied by (i) prior to March 2, 2020, 1.50 , (ii) on or after March 2, 2020 and prior to March 2, 2021, 1.70 and (iii) on or after March 2, 2021, 1.85 , less (b)(i) all Preferred Unit distributions previously made by NRP and (ii) all cash payments previously made in respect of redemption of any PIK Units; and (2) the Per Unit Purchase Price plus the value of all accrued and unpaid distributions. To the extent the holders of the Preferred Units have not elected to convert their Preferred Units before March 2, 2029, NRP has the right to force conversion of the Preferred Units at a price equal to the Liquidation Value divided by an amount equal to a 10% discount to the VWAP for the 30 trading days immediately prior to the notice of conversion. In addition, NRP has the ability to redeem at any time (subject to compliance with its debt agreements) all or any portion of the Preferred Units and any outstanding PIK Units for cash. The redemption price for each outstanding PIK Unit is $1,000 plus the value of any accrued and unpaid distributions per PIK Unit. The redemption price for each Preferred Unit is the Liquidation Value divided by the number of outstanding Preferred Units. The Preferred Units are redeemable at the option of the Preferred Purchasers only upon a change in control. The terms of the Preferred Units contain certain restrictions on NRP's ability to pay distributions on its common units. To the extent that either (i) NRP's consolidated Leverage Ratio, as defined in the Partnership's Fifth Amended and Restated Partnership Agreement dated March 2, 2017 (the "Restated Partnership Agreement"), is greater than 3.25 x, or (ii) the ratio of NRP's Distributable Cash Flow (as defined in the Restated Partnership Agreement) to cash distributions made or proposed to be made is less than 1.2 x (in each case, with respect to the most recently completed four-quarter period), NRP may not increase the quarterly distribution above $0.45 per quarter without the approval of the holders of a majority of the outstanding Preferred Units. In addition, if at any time after January 1, 2022, any PIK Units are outstanding, NRP may not make distributions on its common units until it has redeemed all PIK Units for cash. The holders of the Preferred Units have the right to vote with holders of NRP’s common units on an as-converted basis and have other customary approval rights with respect to changes of the terms of the Preferred Units. In addition, Blackstone has certain approval rights over certain matters as identified in the Restated Partnership Agreement. GoldenTree also has more limited approval rights that will expand once Blackstone's ownership goes below the Minimum Preferred Unit Threshold (as defined below). These approval rights are not transferrable without NRP's consent. In addition, the approval rights held by Blackstone and GoldenTree will terminate at such time that Blackstone (together with their affiliates) or GoldenTree (together with their affiliates), as applicable, no longer own at least 20% of the total number of Preferred Units issued on the closing date, together with all PIK Units that have been issued but not redeemed (the "Minimum Preferred Unit Threshold"). At the closing, pursuant to the Board Representation and Observation Rights Agreement, the Preferred Purchasers received certain board appointment and observation rights, and Blackstone appointed one director and one observer to the Board of Directors of GP Natural Resource Partners LLC. NRP also entered into a registration rights agreement (the "Preferred Unit and Warrant Registration Rights Agreement") with the Preferred Purchasers, pursuant to which NRP is required to file (i) a shelf registration statement to register the common units issuable upon exercise of the Warrants and to cause such registration statement to become effective not later than 90 days following the closing date and (ii) a shelf registration statement to register the common units issuable upon conversion of the Preferred Units and to cause such registration statement to become effective not later than the earlier of the fifth anniversary of the closing date or 90 days following the first issuance of any common units upon conversion of Preferred Units (the "Registration Deadlines"). In addition, the Preferred Unit and Warrant Registration Rights Agreement gives the Preferred Purchasers piggyback registration and demand underwritten offering rights under certain circumstances. The shelf registration statement to register the common units issuable upon exercise of the Warrants became effective on April 20, 2017. If the shelf registration statement to register the common units issuable upon conversion of the Preferred Units is not effective by the applicable Registration Deadline, NRP will be required to pay the Preferred Purchasers liquidated damages in the amounts and upon the term set forth in the Preferred Unit and Warrant Registration Rights Agreement. Accounting for the Preferred Units and Warrants Classification The Preferred Units are accounted for on NRP's consolidated balance sheets as temporary equity due to certain contingent redemption rights that may be exercised at the election of Preferred Purchasers. The Warrants are accounted for on NRP's consolidated balance sheets as equity. Initial Measurement The net transaction price as shown below was allocated to the Preferred Units and Warrants based on their relative fair values at inception date. NRP allocated the transaction issuance costs to the Preferred Units and Warrants primarily on a pro-rata basis based on their relative inception date allocated values. The Preferred Units and Warrants were initially recognized as follows: (In thousands) March 2, 2017 Transaction price, gross $ 250,000 Structuring, origination and other fees to Preferred Purchasers (7,900 ) Transaction costs to other third parties (10,697 ) Transaction price, net $ 231,403 Allocation of net transaction price Preferred Units, net $ 164,587 Warrant holders interest, net 66,816 Transaction price, net $ 231,403 Subsequent Measurement Subsequent adjustment of the Preferred Units will not occur until NRP has determined that the conversion or redemption of all or a portion of the Preferred Units is probable of occurring. Once conversion or redemption becomes probable of occurring, the carrying amount of the Preferred Units will be accreted to their redemption value over the period from the date the feature is probable of occurring to the date the Preferred Units can first be converted or redeemed. During the three months ended March 31, 2018, the Partnership redeemed all of the outstanding PIK Units, which resulted in an $8.8 million cash payment during the period. Activity related to the Preferred Units is as follows: (In thousands, except unit data) Units Outstanding Financial Position Balance at December 31, 2016 — $ — Issuance of Preferred Units, net 250,000 164,587 Distribution paid-in-kind 8,844 8,844 Balance at December 31, 2017 258,844 $ 173,431 Redemption of PIK Units (8,844 ) (8,844 ) Balance at December 31, 2018 250,000 $ 164,587 Subsequent adjustment of the Warrants will not occur until the Warrants are exercised, at which time, NRP may, at its option, elect to settle the Warrants in common units or cash, each on a net basis. The net basis will be equal to the difference between the Partnership's common unit price and the strike price of the Warrant. Once Warrant exercise occurs, the difference between the carrying amount of the Warrants and the net settlement amount will be allocated on a pro-rata basis to the common unitholders and general partner. Certain embedded features within the Preferred Unit and Warrant purchase agreement are accounted for at fair value and are remeasured each quarter. See Note 14. Fair Value Measurements for further information regarding valuation of these embedded derivatives.

Common and Preferred Unit Distr

Common and Preferred Unit Distributions	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Common and Preferred Unit Distributions	Common and Preferred Unit Distributions The Partnership makes cash distributions to common unit holders on a quarterly basis, subject to approval by the Board of Directors. As discussed in Note 5. Class A Convertible Preferred Units and Warrants above, the Partnership also makes distributions to the preferred unitholders. NRP recognizes both Common and Preferred Unit distributions on the date the distribution is declared. Common Unit Distributions Distributions made on the common units and the general partner's general partner ("GP") interest are made on a pro-rata basis in accordance with their relative percentage interests in the Partnership. The general partner is entitled to receive 2% of such distributions. The following table shows the distributions declared and paid to common unitholders during the years ended December 31, 2018 , 2017 and 2016 , respectively: Total Distributions (in thousands) Date Paid Period Covered by Distribution Distribution per Common Unit Common Units GP Interest Total 2018 February 14, 2018 October 1 - December 31, 2017 $ 0.45 $ 5,505 $ 112 $ 5,617 May 14, 2018 January 1 - March 31, 2018 0.45 5,510 113 5,623 August 14, 2018 April 1 - June 30, 2018 0.45 5,511 112 5,623 November 14, 2018 July 1 - September 30, 2018 0.45 5,510 113 5,623 2017 February 14, 2017 October 1 - December 31, 2016 $ 0.45 $ 5,503 $ 112 $ 5,615 May 12, 2017 January 1 - March 31, 2017 0.45 5,506 113 5,619 August 14, 2017 April 1 - June 30, 2017 0.45 5,504 112 5,616 November 14, 2017 July 1 - September 30, 2017 0.45 5,505 112 5,617 2016 February 12, 2016 October 1 - December 31, 2015 $ 0.45 $ 5,503 $ 113 $ 5,616 May 13, 2016 January 1 - March 31, 2016 0.45 5,503 113 5,616 August 12, 2016 April 1 - June 30, 2016 0.45 5,505 112 5,617 November 14, 2016 July 1 - September 30, 2016 0.45 5,503 113 5,616 Preferred Unit Distributions The following table shows the distributions declared and paid to Preferred Unitholders during the years ended December 31, 2018 and 2017 : Date Paid Period Covered by Distribution Distribution per Preferred Unit Total Distribution Declared (in thousands) 2018 February 7, 2018 October 1 - December 31, 2017 $ 30.00 $ 7,765 May 14, 2018 January 1 - March 31, 2018 30.00 7,500 August 14, 2018 April 1 - June 30, 2018 30.00 7,500 November 14, 2018 July 1 - September 30, 2018 30.00 7,500 2017 May 30, 2017 March 2 - March 31, 2017 $ 5.00 $ 2,500 August 29, 2017 April 1 - June 30, 2017 15.00 7,538 November 29, 2017 July 1 - September 30, 2017 15.00 7,650 Income available to common unitholders and the general partner is reduced by Preferred Unit distributions that accumulated during the period. During the year ended December 31, 2018 and 2017 , NRP reduced net income attributable to common unitholders and the general partner by $30.0 million and $25.5 million , respectively as a result of accumulated Preferred Unit distributions earned during the period. The $7.5 million preferred unit distribution earned during the three months ended December 31, 2018 was paid on February 14, 2019.

Net Income Per Common Unit

Net Income Per Common Unit	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Net Income Per Common Unit	Net Income Per Common Unit Basic net income per common unit is computed by dividing net income, after considering income attributable to non-controlling interest, preferred unitholders and the general partner’s general partner interest, by the weighted average number of common units outstanding. Diluted net income per common unit includes the effect of NRP's Preferred Units and Warrants, if the inclusion of these items is dilutive. The dilutive effect of the Preferred Units is calculated using the if-converted method. Under the if-converted method, the Preferred Units are assumed to be converted at the beginning of the period, and the resulting common units are included in the denominator of the diluted net income per unit calculation for the period being presented. Distributions declared in the period and undeclared distributions on the Preferred Units that accumulated during the period are added back to the numerator for purposes of the if-converted calculation. The dilutive effect of the Warrants is calculated using the treasury stock method, which assumes that the proceeds from the exercise of these instruments are used to purchase common units at the average market price for the period. The calculation of the dilutive effect of the Warrants for the years ended December 31, 2018 and 2017 includes the net settlement of Warrants to purchase 1.75 million common units with a strike price of $22.81 but did not include the net settlement of Warrants to purchase 2.25 million common units with a strike price of $34.00 because the impact would have been anti-dilutive. The following table reconciles the numerators and denominators of the basic and diluted net income per common unit computations and calculates basic and diluted net income per common unit: Year Ended December 31, (In thousands, except per unit data) 2018 2017 2016 Allocation of net income: Net income from continuing operations $ 122,360 $ 82,485 $ 90,626 Less: net income attributable to non-controlling interest (510 ) — — Less: income attributable to preferred unitholders (30,000 ) (25,453 ) — Net income from continuing operations attributable to common unitholders and general partner $ 91,850 $ 57,032 $ 90,626 Less: net income from continuing operations attributable to the general partner (1,837 ) (1,141 ) (1,537 ) Net income from continuing operations attributable to common unitholders $ 90,013 $ 55,891 $ 89,089 Net income from discontinued operations $ 17,687 $ 6,182 $ 6,266 Less: net income from discontinued operations attributable to the general partner (354 ) (123 ) (126 ) Net income from discontinued operations attributable to common unitholders $ 17,333 $ 6,059 $ 6,140 Net income $ 140,047 $ 88,667 $ 96,892 Less: net income attributable to non-controlling interest (510 ) — — Less: income attributable to preferred unitholders (30,000 ) (25,453 ) — Net income attributable to common unitholders and general partner $ 109,537 $ 63,214 $ 96,892 Less: net income attributable to the general partner (2,191 ) (1,264 ) (1,663 ) Net income attributable to common unitholders $ 107,346 $ 61,950 $ 95,229 Basic income per common unit: Weighted average common units—basic 12,244 12,232 12,232 Basic net income from continuing operations per common unit $ 7.35 $ 4.57 $ 7.28 Basic net income from discontinued operations per common unit $ 1.42 $ 0.50 $ 0.50 Basic net income per common unit $ 8.77 $ 5.06 $ 7.78 Year Ended December 31, (In thousands, except per unit data) 2018 2017 2016 Diluted income per common unit: Weighted average common units—basic 12,244 12,232 12,232 Plus: dilutive effect of Warrants 511 300 — Plus: dilutive effect of Preferred Units 7,479 9,418 — Weighted average common units—diluted 20,234 21,950 12,232 Net income from continuing operations $ 122,360 $ 82,485 $ 90,626 Less: net income attributable to non-controlling interest (510 ) — — Diluted net income from continuing operations attributable to common unitholders and general partner $ 121,850 $ 82,485 $ 90,626 Less: net income from continuing operations attributable to the general partner (2,437 ) (1,650 ) (1,537 ) Diluted net income from continuing operations attributable to common unitholders $ 119,413 $ 80,835 $ 89,089 Diluted net income from discontinued operations attributable to common unitholders $ 17,333 $ 6,059 $ 6,140 Net income $ 140,047 $ 88,667 $ 96,892 Less: net income attributable to non-controlling interest (510 ) — — Diluted net income attributable to common unitholders and general partner $ 139,537 $ 88,667 $ 96,892 Less: diluted net income attributable to the general partner (2,791 ) (1,773 ) (1,663 ) Diluted net income attributable to common unitholders $ 136,746 $ 86,894 $ 95,229 Diluted net income from continuing operations per common unit $ 5.90 $ 3.68 $ 7.28 Diluted net income from discontinued operations per common unit $ 0.86 $ 0.28 $ 0.50 Diluted net income per common unit $ 6.76 $ 3.96 $ 7.78

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The Partnership's segments are strategic business units that offer distinct products and services to different customers in different geographies within the U.S. and that are managed accordingly. NRP has the following two operating segments: Coal Royalty and Other —consists primarily of coal royalty and coal-related transportation and processing assets. Other assets include industrial minerals royalty properties, aggregates royalty properties, oil and gas royalty properties and timber. The Partnership's coal reserves are primarily located in Appalachia, the Illinois Basin and the Northern Powder River Basin in the United States. The Partnership's aggregates and industrial minerals properties are located in a number of states across the United States. The Partnership's oil and gas royalty assets are primarily located in Louisiana. Soda Ash —consists of the Partnership's 49% non-controlling equity interest in Ciner Wyoming, a trona ore mining operation and soda ash refinery in the Green River Basin of Wyoming. Ciner Resources LP, the Partnership's operating partner, mines the trona, processes it into soda ash, and distributes the soda ash both domestically and internationally to the glass and chemicals industries. In December 2018, the Partnership sold its construction aggregates business for $205 million , before customary purchase price adjustments and transaction expenses, and recorded a gain of $13.1 million . The Partnership's exit from the construction aggregates business enabled it to further reduce debt, focus on its Coal Royalty and Other and Soda Ash business segments and represented a strategic shift as it exited the operations of its construction aggregates business. The gain on sale and operating results of the construction aggregates business is included in Income from discontinued operations on the Consolidated Statements of Comprehensive Income and the net cash proceeds received is included in Cash provided by investing activities of discontinued operations in the Partnership's Consolidated Statements of Cash Flows for the year ended December 31, 2018. See Note 4. Discontinued Operations for more information. Direct segment costs and certain other costs incurred at the corporate level that are identifiable and that benefit the Partnership's segments are allocated to the operating segments accordingly. These allocated costs generally include insurance, taxes, legal, information technology and shared facilities services and are included in Operating and maintenance expenses and Operating and maintenance expenses—affiliates on the Consolidated Statements of Comprehensive Income. Corporate and Financing includes functional corporate departments that do not earn revenues. Costs incurred by these departments include interest and financing, corporate headquarters and overhead, centralized treasury and accounting and other corporate-level activity not specifically allocated to a segment and are included in General and administrative expenses and General and administrative expenses—affiliates on the Consolidated Statements of Comprehensive Income. The following table summarizes certain financial information for each of the Partnership's business segments: Operating Segments (In thousands) Coal Royalty and Other Soda Ash Corporate and Financing Total For the Year Ended December 31, 2018 Revenues (including affiliates) $ 202,765 $ 48,306 $ — $ 251,071 Gain on litigation settlement 25,000 — — 25,000 Gain on asset sales, net 2,441 — — 2,441 Operating and maintenance expenses (including affiliates) 29,509 — — 29,509 Depreciation, depletion and amortization 21,689 — — 21,689 General and administrative (including affiliates) — — 16,496 16,496 Asset impairments 18,280 — — 18,280 Other expense, net — — 70,178 70,178 Net income (loss) from continuing operations 160,728 48,306 (86,674 ) 122,360 Net income from discontinued operations — — — 17,687 As of December 31, 2018 Total assets of continuing operations $ 986,680 $ 247,051 $ 106,923 $ 1,340,654 Total assets of discontinued operations — — — 993 For the Year Ended December 31, 2017 Revenues (including affiliates) $ 202,323 $ 40,457 $ — $ 242,780 Gain on asset sales, net 3,545 — — 3,545 Operating and maintenance expenses 24,883 — — 24,883 Depreciation, depletion and amortization 23,414 — — 23,414 General and administrative (including affiliates) — — 18,502 18,502 Asset impairments 2,967 — — 2,967 Other expense, net — — 94,074 94,074 Net income (loss) from continuing operations 154,604 40,457 (112,576 ) 82,485 Net income from discontinued operations — — — 6,182 As of December 31, 2017 Total assets of continuing operations $ 945,237 $ 245,433 $ 6,129 $ 1,196,799 Total assets of discontinued operations — — — 192,365 For the Year Ended December 31, 2016 Revenues (including affiliates) $ 210,115 $ 40,061 $ — $ 250,176 Gain on asset sales, net 29,068 — — 29,068 Operating and maintenance expenses (including affiliates) 29,890 — — 29,890 Depreciation, depletion and amortization (including affiliates) 31,766 — — 31,766 General and administrative (including affiliates) — — 20,570 20,570 Asset impairments 15,861 — — 15,861 Other expense, net — — 90,531 90,531 Net income (loss) from continuing operations 161,666 40,061 (111,101 ) 90,626 Net income from discontinued operations — — — 6,266 Capital expenditures 5 — — 5

Equity Investment

Equity Investment	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Investment	Equity Investment The Partnership accounts for its 49% investment in Ciner Wyoming using the equity method of accounting. Activity related to this investment is as follows: For the Year Ended December 31, (In thousands) 2018 2017 2016 Balance at beginning of period $ 245,433 $ 255,901 $ 261,942 Income allocation to NRP’s equity interests (1) 53,095 44,846 44,882 Amortization of basis difference (4,789 ) (4,389 ) (4,821 ) Comprehensive income (loss) from unconsolidated investment (138 ) (1,925 ) 448 Distribution (46,550 ) (49,000 ) (46,550 ) Balance at end of period $ 247,051 $ 245,433 $ 255,901 (1) Includes reclassifications of accumulated other comprehensive loss to income allocation to NRP equity interest of $0.5 million , $0.7 million and $0.9 million for the year ended December 31, 2018, 2017 and 2016 , respectively. The difference between the amount at which the investment in Ciner Wyoming is carried and the amount of underlying equity in Ciner Wyoming's net assets was $140.8 million and $145.6 million as of December 31, 2018 and 2017 , respectively. This excess basis relates to property, plant and equipment and right to mine assets. The excess basis difference that relates to property, plant and equipment is being amortized into income using the straight-line method over 28 years. The excess basis difference that relates to right to mine assets is being amortized into income using the units of production method. The following table represents summarized financial information for Ciner Wyoming as derived from the respective financial statements for the years ended December 31, 2018 , 2017 , and 2016 : For the Year Ended December 31, (In thousands) 2018 2017 2016 Sales $ 486,759 $ 497,340 $ 475,187 Gross profit 104,053 114,202 114,232 Net income 108,357 91,523 91,596 The financial position of Ciner Wyoming is summarized as follows: December 31, (In thousands) 2018 2017 Current assets $ 138,080 $ 180,433 Noncurrent assets 252,743 228,002 Current liabilities 64,012 56,219 Noncurrent liabilities 109,921 148,401

Plant and Equipment, Net

Plant and Equipment, Net	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Plant and Equipment	Plant and Equipment, Net The Partnership’s plant and equipment consist of the following: December 31, (In thousands) 2018 2017 Plant and equipment at cost $ 6,865 $ 6,865 Less: accumulated depreciation (5,881 ) (5,517 ) Total plant and equipment, net $ 984 $ 1,348 Depreciation expense included in Depreciation, depletion and amortization on the Partnership's Consolidated Statements of Comprehensive Income totaled $0.4 million , $0.4 million and $0.8 million for the year ended December 31, 2018 , 2017 and 2016 , respectively. Impairment expense related to the Partnership's plant and equipment included in Asset impairments on the Consolidated Statements of Comprehensive Income totaled $2.0 million for the year ended December 31, 2016 .

Mineral Rights, Net

Mineral Rights, Net	12 Months Ended
	Dec. 31, 2018
Extractive Industries [Abstract]
Mineral Rights	Mineral Rights, Net The Partnership’s mineral rights consist of the following: December 31, 2018 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,164,845 $ (451,210 ) $ 713,635 Aggregates properties 24,920 (11,814 ) 13,106 Oil and gas royalty properties 12,395 (7,632 ) 4,763 Other 13,158 (1,550 ) 11,608 Total mineral rights, net $ 1,215,318 $ (472,206 ) $ 743,112 December 31, 2017 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,170,104 $ (436,964 ) $ 733,140 Aggregates properties 37,942 (9,602 ) 28,340 Oil and gas royalty properties 12,395 (7,158 ) 5,237 Other 13,168 (1,466 ) 11,702 Total mineral rights, net $ 1,233,609 $ (455,190 ) $ 778,419 Depletion expense related to the Partnership’s mineral rights is included in Depreciation, depletion and amortization on the Partnership's Consolidated Statements of Comprehensive Income and totaled $17.0 million , $20.1 million and $27.8 million for the year ended December 31, 2018 , 2017 and 2016 , respectively. Sales of Mineral Rights During the year ended December 31, 2018, the Partnership sold mineral reserves in its Coal Royalty and Other segment in multiple transactions for cumulative gross proceeds of $2.4 million and recorded a cumulative gain of $2.4 million included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income. During the year ended December 31, 2017, the Partnership sold mineral reserves in its Coal Royalty and Other segment in multiple transactions for cumulative gross proceeds of $1.0 million and recorded a cumulative gain of $3.5 million included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income. During the year ended December 31, 2016, the Partnership sold the following assets: 1) Oil and gas royalty and overriding royalty interests in the Coal Royalty and Other segment in several producing properties located in the Appalachian Basin for $36.4 million gross sales proceeds. The effective date of the sale was January 1, 2016, and the Partnership recorded an $18.6 million gain from this sale included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income. 2) Aggregates reserves and related royalty rights in the Coal Royalty and Other segment at three aggregates operations located in Texas, Georgia and Tennessee for $10.0 million gross sales proceeds. The effective date of the sale was February 1, 2016, and the Partnership recorded a $1.5 million gain from this sale included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income. In addition to the two asset sales described above, during the year ended December 31, 2016, the Partnership sold mineral reserves within its Coal Royalty and Other segment in multiple sale transactions for $17.3 million of cumulative gross sales proceeds and recorded a cumulative gain of $8.6 million from these sale transactions that are included in Gain on asset sales, net on its Consolidated Statement of Comprehensive Income. These amounts primarily relate to eminent domain transactions with governmental agencies and the sale of additional oil and gas royalty interests. Impairment of Mineral Rights During the years ended December 31, 2018 , 2017 and 2016 , the Partnership identified facts and circumstances that indicated that the carrying value of certain of its mineral rights exceed future cash flows from those assets and recorded non-cash impairment expense included in Asset impairments on the Consolidated Statements of Comprehensive Income as follows: For the Years Ended December 31, (In thousands) 2018 2017 2016 Coal properties (1) $ 5,259 $ 595 $ 12,088 Oil and gas properties — — 36 Aggregates and timber royalty properties (2) 13,021 2,372 1,677 Total $ 18,280 $ 2,967 $ 13,801 (1) The Partnership recorded $5.3 million of coal property impairments during the year ended December 31, 2018 primarily as a result of lease terminations, of which it recorded $5.0 million of impairment expense to fully impair certain coal properties during the three months ended December 31, 2018. The Partnership recorded $0.6 million of coal property impairments during the year ended December 31, 2017. The Partnership recorded $12.1 million of coal property impairments during the year ended December 31, 2016 primarily as a result of lease surrender and termination. The Partnership recorded $3.8 million of coal property impairment during the three months ended September 30, 2016 and the fair value of the impaired asset was reduced to $4.0 million at September 30, 2016. The Partnership recorded $8.2 million of impairment expense to fully impair certain coal property impairment during the three months ended December 31, 2016. (2) During the three months ended December 31, 2018, the Partnership recorded $13.0 million of impairment expense related to an aggregates property that the Partnership owns and leases to its former construction aggregates business, which mines, produces and sells the aggregates. The fair value of the impaired asset was reduced to $2.3 million at December 31, 2018. The Partnership recorded $2.4 million and $1.7 million of aggregates and timber royalty properties impairments during the year ended December 31, 2017 and 2016, respectively.

Intangible Assets, Net

Intangible Assets, Net	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets (Including Affiliate)	The Partnership's intangible assets consist of above-market coal and related transportation contracts with subsidiaries of Foresight Energy in which the Partnership receives throughput fees for the handling and transportation of coal. The Partnership's intangible assets included on its Consolidated Balance Sheets are as follows: December 31, (In thousands) 2018 2017 Intangible assets $ 81,109 $ 81,109 Less: accumulated amortization (38,596 ) (34,289 ) Total intangible assets, net $ 42,513 $ 46,820 Amortization expense included in Depreciation, depletion and amortization on the Partnership's Consolidated Statements of Comprehensive Income was $4.3 million and $2.0 million for the years ended December 31, 2018 and 2017 , respectively. Amortization expense included in Amortization expense—affiliates on the Partnership's Consolidated statements of Comprehensive income was $1.0 million and $3.2 million for the years ended December 31, 2017 and 2016 , respectively. As of May 9, 2017, Foresight Energy was no longer deemed to be an affiliate of the Partnership. Refer to Note 15. Related Party Transactions for additional details. The estimates of amortization expense for the years ended December 31, as indicated below, are based on current mining plans and are subject to revision as those plans change in future periods. (In thousands) Estimated Amortization Expense 2019 $ 3,251 2020 3,741 2021 3,660 2022 3,636 2023 3,602 The weighted average remaining amortization period for contract intangibles was 16 years .

Debt, Net

Debt, Net	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt, Net The Partnership's debt consists of the following: December 31, (In thousands) 2018 2017 NRP LP debt: 10.500% senior notes, with semi-annual interest payments in March and September, due March 2022, $241 million issued at par and $105 million issued at 98.75% $ 345,638 $ 345,638 Opco debt: Revolving credit facility — 60,000 Senior notes 4.91% with semi-annual interest payments in June and December, with annual principal payments in June, due June 2018 — 4,586 8.38% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2019 21,319 42,670 5.05% with semi-annual interest payments in January and July, with annual principal payments in July, due July 2020 15,290 22,946 5.55% with semi-annual interest payments in June and December, with annual principal payments in June, due June 2023 13,414 16,115 4.73% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2023 37,195 44,693 5.82% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 89,529 104,520 8.92% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 27,185 31,733 5.03% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 107,013 120,547 5.18% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 30,555 34,396 Total debt at face value $ 687,138 $ 827,844 Net unamortized debt discount (1,266 ) (1,661 ) Net unamortized debt issuance costs (13,114 ) (16,835 ) Total debt, net $ 672,758 $ 809,348 Less: current portion of long-term debt 115,184 79,740 Total long-term debt, net $ 557,574 $ 729,608 NRP LP Debt 2022 Senior Notes In March 2017, NRP and NRP Finance issued $346 million aggregate principal amount of 2022 Senior Notes to several holders of their 2018 Senior Notes. Of the $346 million of 2022 Senior Notes issued, $241 million in aggregate principal amount were issued in exchange for $241 million in aggregate principal amount of 2018 Senior Notes, and $105 million of the 2022 Senior Notes were issued to the holders for cash. The 2022 Senior Notes are issued under an Indenture dated as of March 2, 2017 (the "Indenture"), bear interest at 10.500% per year, are payable semi-annually on March 15 and September 15, beginning September 15, 2017, and mature on March 15, 2022. The $105.0 million in 2022 Senior Notes purchased for cash were issued at a price of 98.75% (original issue discount of 1.25% ), and each holder exchanging 2018 Senior Notes received a fee of 5.813% of the aggregate principal amount of all 2018 Senior Notes tendered for exchange by such holder, as well as all accrued and unpaid interest thereon. The 5.813% fee included a 4.563% call premium on the early repayment of the 2018 Senior Notes and a 1.25% fee on the exchange of the 2018 Notes for 2022 Senior Notes. This fee is accounted for as a debt issuance cost, capitalized and shown net of the debt liability on the Partnership's Consolidated Balance Sheets. NRP and NRP Finance have the option to redeem the 2022 Senior Notes, in whole or in part, at any time on or after March 15, 2019, at the redemption prices (expressed as percentages of principal amount) of 105.25% for the 12-month period beginning March 15, 2019, 102.625% for the 12-month period beginning March 15, 2020, and thereafter at 100.000% , together, in each case, with any accrued and unpaid interest to the date of redemption. Furthermore, before March 15, 2019, NRP may on any one or more occasions redeem up to 35% of the aggregate principal amount of the 2022 Senior Notes with the net proceeds of certain public or private equity offerings at a redemption price of 110.500% of the principal amount of 2022 Senior Notes, plus any accrued and unpaid interest, if any, to the date of redemption, if at least 65% of the aggregate principal amount of the 2022 Senior Notes issued under the 2022 Indenture remains outstanding immediately after such redemption and the redemption occurs within 180 days of the closing date of such equity offering. In the event of a change of control, as defined in the 2022 Indenture, the holders of the 2022 Senior Notes may require the Partnership to purchase their 2022 Senior Notes at a purchase price equal to 101% of the principal amount of the 2022 Senior Notes, plus accrued and unpaid interest, if any. The 2022 Indenture contains restrictive covenants that are substantially similar to those contained in the Indenture governing the 2018 Senior Notes, except that the debt incurrence and restricted payments covenants contain additional restrictions. Under the debt incurrence covenant, NRP's non-guarantor restricted subsidiaries will not be permitted to incur additional indebtedness unless their consolidated leverage ratio is less than 3.00 x (measured on a pro forma basis and assuming that the greater of (i) $150.0 million of debt (or, if less, at NRP's election, the amount of total lending commitments under any revolving credit facility) and (ii) the actual amount of debt outstanding is outstanding under any revolving credit facility); provided, however, that such non-guarantor restricted subsidiaries will be permitted to make up to $150 million in borrowings under a revolving credit facility (which amount will be reduced on a dollar-for-dollar basis to the extent NRP has made the election described in clause (i) above). Under the restricted payments covenant, NRP will not be able to increase the quarterly distribution on its common units or elect to pay more than 50% of the distributions required to be made on the Preferred Units in cash, unless, in each case, its consolidated leverage ratio is less than 4.00 x. The 2022 Indenture also contains restrictions on NRP's ability to redeem the Preferred Units. The 2022 Senior Notes are the senior unsecured obligations of NRP and NRP Finance. The 2022 Senior Notes rank equal in right of payment to all existing and future senior unsecured debt of NRP and NRP Finance and senior in right of payment to any of NRP's subordinated debt. The 2022 Senior Notes are effectively subordinated in right of payment to all future secured debt of NRP and NRP Finance to the extent of the value of the collateral securing such indebtedness and are structurally subordinated in right of payment to all existing and future debt and other liabilities of our subsidiaries, including the Opco Credit Facility and each series of Opco’s existing Senior Notes, as defined below. None of NRP's subsidiaries guarantee the 2022 Senior Notes. As of December 31, 2018 and December 31, 2017 , NRP and NRP Finance were in compliance with the terms of their debt agreements. Opco Debt All of Opco’s debt is guaranteed by its wholly owned subsidiaries and is secured by certain of the assets of Opco and its wholly owned subsidiaries other than NRP Trona LLC. As of December 31, 2018 and 2017 , Opco was in compliance with the terms of the financial covenants contained in its debt agreements. Opco Credit Facility Opco’s Third Amended and Restated Credit Agreement, as amended (the "Opco Credit Facility"), matures on April 30, 2020. As of December 31, 2018 , Opco had $100 million in available borrowing capacity under the Opco Credit Facility. As discussed in Note 4. Discontinued Operations , in December 2018 the Partnership repaid the outstanding balance of the Opco Credit Facility as a result of the sale of its construction aggregates business. Indebtedness under the Opco Credit Facility bears interest, at Opco's option, at: • the higher of (i) the prime rate as announced by the agent bank; (ii) the federal funds rate plus 0.50% ; or (iii) LIBOR plus 1% , in each case plus an applicable margin ranging from 2.50% to 3.50% ; or • a rate equal to LIBOR plus an applicable margin ranging from 3.50% to 4.50% . The weighted average interest rates for the borrowings outstanding under the Opco Credit Facility for the years ended December 31, 2018 and 2017 were 6.23% and 5.32% , respectively. Debt issuance costs related to the OpCo credit facility were $1.7 million and $4.6 million at December 31, 2018 and 2017 , respectively and have been capitalized and included in Other assets on the Partnership's Consolidated Balance Sheets. Opco will incur a commitment fee on the unused portion of the revolving credit facility at a rate of 0.50% per annum. Opco may prepay all amounts outstanding under the Opco Credit Facility at any time without penalty. The Opco Credit Facility contains financial covenants requiring Opco to maintain: • a leverage ratio of consolidated indebtedness to EBITDDA (as defined in the Opco Credit Facility) not to exceed 4.0 x; provided, however, that if NRP increases its quarterly distribution to its common unitholders above $0.45 per common unit, the maximum leverage ratio under the Opco Credit Facility will permanently decrease from 4.0 x to 3.0 x; and • a fixed charge coverage ratio of consolidated EBITDDA to consolidated fixed charges (consisting of consolidated interest expense and consolidated lease expense) of not less than 3.5 to 1.0. The Opco Credit Facility contains certain additional customary negative covenants that, among other items, restrict Opco’s ability to incur additional debt, grant liens on its assets, make investments, sell assets and engage in business combinations. Included in the investment covenant are restrictions upon Opco’s ability to acquire assets where Opco does not maintain certain levels of liquidity. In addition, Opco is required to use 75% of the net cash proceeds of certain non-ordinary course asset sales to repay the Opco Credit Facility (without any corresponding commitment reduction) and use the remaining 25% of the net cash proceeds to offer to repay its Senior Notes on a pro-rata basis, as described below under “—Opco Senior Notes.” The Opco Credit Facility also contains customary events of default, including cross-defaults under Opco’s Senior Notes. The Opco Credit Facility is collateralized and secured by liens on certain of Opco’s assets with carrying values of $548.9 million and $553.9 million classified as Plant and equipment and Mineral rights as of December 31, 2018 and 2017 , respectively, and $95.7 million included in Long-term assets of discontinued operations on the Partnership’s Consolidated Balance Sheets as of December 31, 2017. The collateral includes (1) the equity interests in all of Opco’s wholly owned subsidiaries, other than NRP Trona LLC (which owns a 49% non-controlling equity interest in Ciner Wyoming), (2) the personal property and fixtures owned by Opco’s wholly owned subsidiaries, other than NRP Trona LLC, (3) Opco’s material coal royalty revenue producing properties, and (4) certain of Opco’s coal-related infrastructure assets. Opco Senior Notes Opco has issued several series of private placement senior notes (the "Opco Senior Notes") with various interest rates and principal due dates. As of December 31, 2018 and 2017 , the Opco Senior Notes had cumulative principal balances of $341.5 million and $422.2 million , respectively. Opco made mandatory principal payments on the Opco Senior Notes of $80.7 million , $80.8 million and $82.9 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. As discussed in Note 4. Discontinued Operations , as a result of the sale of the Partnership's construction aggregates business, $49 million was offered to the holders of the Opco Senior Notes and paid during the first quarter of 2019. The remaining $55 million of net cash proceeds from the sale of the construction aggregates business is restricted and the Partnership intends to use these remaining proceeds to repay its Opco Senior Notes as they amortize in 2019. The Note Purchase Agreements relating to the Opco Senior Notes contain covenants requiring Opco to: • maintain a ratio of consolidated indebtedness to consolidated EBITDDA (as defined in the note purchase agreement) of no more than 4.0 to 1.0 for the four most recent quarters; • not permit debt secured by certain liens and debt of subsidiaries to exceed 10% of consolidated net tangible assets (as defined in the note purchase agreement); and • maintain the ratio of consolidated EBITDDA (as defined in the note purchase agreement) to consolidated fixed charges (consisting of consolidated interest expense and consolidated operating lease expense) at not less than 3.5 to 1.0. In addition, the Note Purchase Agreements include a covenant that provides that, in the event NRP Operating or any of its subsidiaries is subject to any additional or more restrictive covenants under the agreements governing its material indebtedness (including the Opco Credit Facility and all renewals, amendments or restatements thereof), such covenants shall be deemed to be incorporated by reference in the Note Purchase Agreements and the holders of the Notes shall receive the benefit of such additional or more restrictive covenants to the same extent as the lenders under such material indebtedness agreement. The 8.38% and 8.92% Opco Senior Notes also provide that in the event that Opco’s leverage ratio of consolidated indebtedness to consolidated EBITDDA (as defined in the Note Purchase Agreements) exceeds 3.75 to 1.00 at the end of any fiscal quarter, then in addition to all other interest accruing on these notes, additional interest in the amount of 2.00% per annum shall accrue on the notes for the two succeeding quarters and for as long thereafter as the leverage ratio remains above 3.75 to 1.00. Opco has not exceeded the 3.75 to 1.00 ratio at the end of any fiscal quarter through December 31, 2018 . In September 2016, Opco amended the Opco Senior Notes. Under this amendment, Opco agreed to use certain asset sale proceeds to make mandatory prepayment offers on the Opco Senior Notes as follows: • until the earlier of the time that (1) Opco has sold $300 million of assets and (2) June 30, 2020, Opco will be required to make prepayment offers to the holders of the Opco Senior Notes using 25% of the net cash proceeds from certain asset sales; and • after the earlier to occur of the dates above, Opco will be required to make prepayment offers to the holders of the Opco Senior Notes using an amount of net cash proceeds from certain asset sales that will be calculated pro-rata based on the amount of Opco Senior Notes then outstanding compared to the other total Opco senior debt outstanding that is being prepaid. The mandatory prepayment offers described above will be made pro-rata across each series of outstanding Opco Senior Notes and will not require any make-whole payment by Opco. In addition, the remaining principal and interest payments on the Opco Senior Notes will be adjusted accordingly based on the amount of Opco Senior Notes actually prepaid. The prepayments do not affect the maturity dates of any series of the Opco Senior Notes. Consolidated Principal Payments The consolidated principal payments due are set forth below: NRP LP Opco (In thousands) Senior Notes (1) Senior Notes Credit Facility Total 2019 $ — $ 116,125 $ — $ 116,125 2020 — 46,436 — 46,436 2021 — 39,634 — 39,634 2022 345,638 39,634 — 385,272 2023 — 39,634 — 39,634 Thereafter — 60,037 — 60,037 $ 345,638 $ 341,500 $ — $ 687,138 (1) The 10.500% senior notes due 2022 were issued at a discount and were carried at $344.4 million and $344.0 million as of December 31, 2018 and 2017 , respectively.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value of Financial Assets and Liabilities The Partnership’s financial assets and liabilities consist of cash and cash equivalents, restricted cash, contracts receivable, debt, Preferred Units and Warrants. The carrying amounts reported on the Consolidated Balance Sheets for cash and cash equivalents and restricted cash approximate fair value due to their short-term nature. There were no transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy during the years ended December 31, 2018 or 2017 . The Partnership uses available market data and valuation methodologies to estimate the fair value of debt. The fair value of debt is the estimated amount the Partnership would have to pay a third party to assume the debt, including a credit spread for the difference between the issue rate and the period end market rate. The credit spread is the Partnership's default or repayment risk. The following table shows the carrying amount and estimated fair value of the Partnership's debt and contracts receivable: December 31, 2018 December 31, 2017 (In thousands) Carrying Value Estimated Carrying Estimated Debt: NRP 2022 Senior Notes (1) $ 334,024 $ 356,871 $ 330,404 $ 366,376 Opco Senior Notes (2) 338,734 352,599 418,944 447,538 Opco Revolving Credit Facility (3) — — 60,000 60,000 Assets: Contracts receivable, current and long-term (4) $ 40,776 $ 34,704 $ 43,826 $ 30,517 (1) The Level 1 fair value is based upon quotations obtained for identical instruments on the closing trading prices near period end. (2) Due to no observable quoted prices on these instruments, the Level 3 fair value is estimated by management using quotations obtained for the NRP Senior Notes on the closing trading prices near period end. (3) The Level 3 fair value approximates the outstanding borrowing amount because the interest rates are variable and reflective of market rates and the terms of the credit facility allow the Partnership to repay this debt at any time without penalty. (4) The Level 3 fair value is determined based on the present value of future cash flow projections related to the underlying assets. NRP has embedded derivatives in the Preferred Units related to certain conversion options, redemption features and the change of control provision that are accounted for separately from the Preferred Units as assets and liabilities at fair value on the Partnership's Consolidated Balance Sheets. Level 3 valuation of the embedded derivatives are based on numerous factors including the likelihood of the event occurring. The embedded derivatives are revalued quarterly, and changes in their fair value would be recorded in Other expense, net in the Partnership's Consolidated Statements of Comprehensive Income. The embedded derivatives had zero value as of December 31, 2018 and 2017 . Fair Value of Non-Financial Assets The Partnership discloses or recognizes its non-financial assets, such as impairments of coal and aggregates properties and other assets, at fair value on a nonrecurring basis. Refer to Note 10. Plant and Equipment, Net and Note 11. Mineral Rights, Net for additional disclosures related to the fair value associated with the impaired assets.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Cline Affiliates and Foresight Energy Mr. Chris Cline, both individually and through another affiliate, Adena Minerals, LLC ("Adena"), owned a 31% interest in NRP (GP) LP, NRP's general partner ("NRP GP"), through May 9, 2017. On May 9, 2017, Adena sold its 31% limited partner interest in NRP GP to Great Northern Properties Limited Partnership (“GNPLP”) and Western Pocahontas Properties Limited Partnership ("WPPLP") (the “Adena Sale”). GNPLP and WPPLP are companies controlled by Corbin J. Robertson, the Chairman and Chief Executive Officer of GP Natural Resource Partners LLC (the general partner of NRP GP) (“GP LLC”). Upon closing of this transaction, NRP no longer considers the various companies affiliated with Chris Cline, including Foresight Energy to be affiliates of NRP. As a result, all transactions (including revenues, expenses and cash flows) after May 9, 2017 with the various companies affiliated with Chris Cline, including Foresight Energy, are considered to be third party transactions. Revenues and expenses related to transactions with Foresight Energy are included in the Partnership's Consolidated Statements of Comprehensive Income as follows: For the Years Ended December 31, (In thousands) 2018 2017 2016 Revenues: Coal royalty and other $ 30,777 $ 28,763 $ — Coal royalty and other — affiliates — 21,204 44,019 Transportation and processing services 23,818 14,510 — Transportation and processing services—affiliate — 6,012 19,336 Total $ 54,595 $ 70,489 $ 63,355 Expenses: Operating and maintenance expense $ 1,761 $ 1,066 $ — Operating and maintenance expense—affiliates — 452 1,347 Total $ 1,761 $ 1,518 $ 1,347 Coal Royalty and Other Revenues Various subsidiaries of Foresight Energy lease coal reserves from the Partnership. In addition, NRP owns a contractual overriding royalty interest at Foresight Energy's Sugar Camp mine in the Illinois Basin which provides for payments based upon production from specific tons at Foresight Energy's Sugar Camp operations on certain reserves owned by another affiliate of Chris Cline. This overriding royalty is accounted for as a financing arrangement. Revenues related to these transactions are included in Coal royalty and other revenues in the Partnership's Consolidated Statements of Comprehensive Income. Transportation and Processing Services Revenues and Expenses The Partnership owns transportation and processing infrastructure related to certain of its coal properties, including loadout and other transportation assets at Foresight Energy's Williamson and Macoupin mines in the Illinois Basin, for which it collects throughput fees. These fees are included in Transportation and processing services revenues in the Partnership's Consolidated Statements of Comprehensive Income. NRP is responsible for operating and maintaining the rail loadout transportation assets at the Williamson mine and subcontracts the operating responsibilities to a subsidiary of Foresight Energy. Expenses related to these operations are included in Operating and maintenance expenses in the Partnership's Consolidated Statements of Comprehensive Income. In addition, NRP owns rail loadout and associated infrastructure at the Sugar Camp mine, an Illinois Basin mine also operated by a subsidiary of Foresight Energy LP. While the Partnership owns coal reserves at the Williamson and Macoupin mines, it does not own coal reserves at the Sugar Camp mine. The infrastructure at the Sugar Camp mine is leased to a subsidiary of Foresight Energy and NRP collects throughput fees, which are included in Transportation and processing services revenues in the Partnership's Consolidated Statements of Comprehensive Income. NRP's Sugar Camp rail loadout lease with a subsidiary of Foresight Energy is accounted for as a financing lease. Minimum lease payments are $5.0 million per year for the next five years and represent a $1.25 million per quarter deficiency payment. The following table shows certain amounts related to NRP's Sugar Camp rail loadout facility financing lease: December 31, (In thousands) 2018 2017 Projected remaining payments $ 66,495 $ 71,452 Unearned income 25,058 28,366 Reimbursements to Affiliates of our General Partner The Partnership’s general partner does not receive any management fee or other compensation for its management of NRP. However, in accordance with the partnership agreement, the general partner and its affiliates are reimbursed for services provided to the Partnership and for expenses incurred on the Partnership’s behalf. Employees of Quintana Minerals Corporation ("QMC") and WPPLP, affiliates of the Partnership, provide their services to manage the Partnership's business. QMC and WPPLP charge the Partnership the portion of their employee salary and benefits costs related to their employee services provided to NRP. These QMC and WPPLP employee management service costs are presented as Operating and maintenance expenses—affiliates and General and administrative—affiliates on the Partnership's Consolidated Statements of Comprehensive Income. NRP also reimburses overhead costs incurred by its affiliates to manage the Partnership's business. These overhead costs include certain rent, legal, accounting, treasury, information technology, insurance, administration of employee benefits and other corporate services incurred by or on behalf of the Partnership’s general partner and its affiliates and are presented as Operating and maintenance expenses—affiliates and General and administrative—affiliates on the Partnership's Consolidated Statements of Comprehensive Income. Direct general and administrative expenses charged to the Partnership by QMC and WPPLP are included in the Partnership's Consolidated Statement of Comprehensive Income as follows: For the Years Ended December 31, (In thousands) 2018 2017 2016 Operating and maintenance expenses—affiliates $ 6,170 $ 6,184 $ 8,119 General and administrative—affiliates 3,658 4,989 3,591 During the years ended December 31, 2018 , 2017 and 2016 , the Partnership recognized $5.4 million , $1.5 million and $0.7 million in Operating and maintenance expenses—affiliates, respectively, on its Consolidated Statements of Comprehensive Income related to a non-participating production royalty payable to WPPLP pursuant to a conveyance agreement entered into in 2007 in which coal royalty revenues received from a third party by NRP are passed back to WPPLP. Included in Income from discontinued operations on the Partnership's Consolidated Statements of Income are $1.0 million , $1.4 million and $3.1 million of Operating and maintenance expenses charged by QMC for the years ended December 31, 2018 , 2017 and 2016 , respectively. At December 31, 2017 , the Partnership had Other assets—affiliate from WPPLP on its Consolidated Balance Sheets related to a non-production royalty receivable from WPPLP for overriding royalty interest of $0.2 million . The Partnership had Accounts payable—affiliates on its Consolidated Balance Sheets to QMC of $0.5 million and WPPLP of $1.4 million as of December 31, 2018 and to QMC of $0.4 million and WPPLP of $0.1 million as of December 31, 2017 . Included in Liabilities from discontinued operations on the Partnerships Consolidated Balance Sheets is $0.1 million in Accounts payable, affiliates, due to QMC as of December 31, 2018 and 2017 , respectively. Quintana Capital Group GP, Ltd. Corbin J. Robertson, Jr. is a principal in Quintana Capital Group GP, Ltd. ("Quintana Capital"), which controls several private equity funds focused on investments in the energy business. In connection with the formation of Quintana Capital, the Partnership adopted a formal conflicts policy that establishes the opportunities that will be pursued by the Partnership and those that will be pursued by Quintana Capital. The governance documents of Quintana Capital’s affiliated investment funds reflect the guidelines set forth in the Partnership's conflicts policy. At December 31, 2018 , a fund controlled by Quintana Capital owned a substantial interest in Corsa Coal Corp. ("Corsa"), a coal mining company traded on the TSX Venture Exchange that is one of the Partnership’s lessees in Tennessee. During the second quarter of 2018, Corsa assigned its lease with NRP to a third party and is no longer deemed a related party. Coal related revenues from Corsa totaled $0.5 million , $1.3 million and $2.2 million for the years ended December 31, 2018 , 2017 and 2016 . At December 31, 2017 , the Partnership had Accounts receivable—affiliates totaling $0.2 million from Corsa on its Consolidated Balance Sheet. Quinwood Coal Company Royalty In May 2017, a subsidiary of Alpha Natural Resources assigned two coal leases with us to Quinwood Coal Company ("Quinwood"), an entity wholly owned by Corbin J. Robertson III. In connection with this lease assignment, Quinwood forfeited the historical recoupable balance related to this property. As a result, NRP recognized $0.9 million of deferred minimum payments received in prior periods from a subsidiary of Alpha as Coal royalty and other—affiliates revenue on its Consolidated Statements of Comprehensive Income during the year ended December 31, 2017 .

Major Customers

Major Customers	12 Months Ended
	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Major Customers	Major Customers Revenues from customers that exceeded 10 percent of total revenues for any of the periods presented below are as follows: For the Years Ended December 31, 2018 2017 2016 (In thousands) Revenues Percent Revenues Percent Revenues Percent Foresight Energy $ 54,595 21.7 % $ 70,489 29.0 % $ 63,355 25.3 % Revenues from Foresight Energy are included within the Partnership's Coal Royalty and Other segment.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal NRP is involved, from time to time, in various legal proceedings arising in the ordinary course of business. While the ultimate results of these proceedings cannot be predicted with certainty, Partnership management believes these claims will not have a material effect on the Partnership’s financial position, liquidity or operations. During the year ended 2018, NRP was also involved in the matters described below. Anadarko Contingent Consideration Payment Dispute In January 2013, NRP acquired a non-controlling 48.51% general partner interest in OCI Wyoming, L.P. ("OCI LP") and all of the preferred stock and a portion of the common stock of OCI Wyoming Co. ("OCI Co") (which in turn owned a 1% limited partner interest in OCI LP) from Anadarko Holding Company and its subsidiary, Big Island Trona Company (together, "Anadarko"). The remaining general partner interest in OCI LP and common stock of OCI Co were owned by subsidiaries of OCI Chemical Corporation. The acquisition agreement provided for additional contingent consideration of up to $50 million to be paid by NRP if certain performance criteria were met at OCI LP as defined in the purchase and sale agreement in any of the years 2013, 2014 or 2015. For those years, NRP paid an aggregate of $11.5 million to Anadarko in full satisfaction of these contingent consideration payment obligations. In July 2013, pursuant to a series of transactions in connection with an initial public offering by a subsidiary of OCI Chemical Corporation, the ownership structure in OCI LP was simplified. In connection with such reorganization, NRP exchanged the stock of OCI Co for a limited partner interest in OCI LP. Following the reorganization, NRP's interest in OCI LP increased to 49% , consisting of both limited and general partner interests. The restructuring did not have any impact on the operations, revenues, management or control of OCI LP. In July 2017, Anadarko filed a lawsuit against Opco and NRP Trona LLC in the District Court of Harris County, Texas, 157th Judicial District. The complaint alleged that the transactions conducted in 2013 triggered an acceleration of NRP's obligation under the purchase agreement with Anadarko to pay additional contingent consideration in full and demanded immediate payment of such amount, together with interest, court costs and attorneys’ fees. NRP does not believe the reorganization transactions triggered an obligation to pay any additional contingent consideration and is vigorously defending this lawsuit. However, the ultimate outcome cannot be predicted with certainty and the Partnership estimates a possible range of loss between $0 , if it prevails, and approximately $40 million , plus interest, court costs and attorneys’ fees if Anadarko prevails and is awarded the full damages it seeks. Foresight Energy Settlement In October 2018, NRP's lawsuits against Foresight Energy and its subsidiaries Hillsboro Energy and Macoupin Energy were settled. The Hillsboro suit was pending in the Circuit Court of the Fourth Judicial Circuit in Montgomery County, Illinois, and the Macoupin suit was pending in Macoupin County, Illinois. NRP received a payment of $25 million from Foresight Energy in full settlement of the Hillsboro litigation, which was recognized immediately as Gain on litigation settlement in the Consolidated Statement of Comprehensive Income. In addition, NRP and Hillsboro Energy amended the coal mining lease with respect to the Deer Run mine to change the $30 million recoupable annual minimum royalty payments to $11 million non-recoupable annual minimum payments effective January 1, 2019 and extended the current lease term through the end of 2033. Furthermore, Foresight Energy forfeited its recoupable balances under the Macoupin and Hillsboro leases totaling approximately $37.4 million , the majority of which NRP previously recognized in Cumulative effect of adoption of accounting standard in Partners' capital on its Consolidated Balance Sheet on January 1, 2018. All claims were dismissed in both the Hillsboro and Macoupin lawsuits. Environmental Compliance The operations the Partnership’s lessees conduct on its properties, as well as the aggregates/industrial minerals and oil and gas operations in which the Partnership has interests, are subject to federal and state environmental laws and regulations. See " Items 1. and 2. Business and Properties—Regulation and Environmental Matters ." As an owner of surface interests in some properties, the Partnership may be liable for certain environmental conditions occurring on the surface properties. The terms of substantially all of the Partnership’s coal leases require the lessee to comply with all applicable laws and regulations, including environmental laws and regulations. Lessees post reclamation bonds assuring that reclamation will be completed as required by the relevant permit, and substantially all of the leases require the lessee to indemnify the Partnership against, among other things, environmental liabilities. Some of these indemnifications survive the termination of the lease. The Partnership makes regular visits to the mines to ensure compliance with lease terms, but the duty to comply with all regulations rests with the lessees. The Partnership believes that its lessees will be able to comply with existing regulations and does not expect that any lessee’s failure to comply with environmental laws and regulations to have a material impact on the Partnership’s financial condition or results of operations. The Partnership has neither incurred, nor is aware of, any material environmental charges imposed on the Partnership related to its properties for the period ended December 31, 2018. The Partnership is not associated with any material environmental contamination that may require remediation costs. However, the Partnership’s lessees do conduct reclamation work on the properties under lease to them. Because the Partnership is not the permittee of the mines being reclaimed, the Partnership is not responsible for the costs associated with these reclamation operations. As a former owner of the working interests in oil and natural gas operations, the Partnership is responsible for its proportionate share of any losses and liabilities, including environmental liabilities, arising from uninsured and underinsured events during the period it was an owner.

Unit-Based Compensation

Unit-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Unit-Based Compensation	Unit-Based Compensation 2017 Long-Term Incentive Plan In December 2017, the 2017 Long-Term Incentive Plan (the “2017 LTIP”) was approved and it became effective in January 2018. The 2017 LTIP authorizes 800,000 common units that are available for delivery by the Partnership pursuant to awards under the plan. The term is 10 years from the date of Board approval or, if earlier, the date the 2017 LTIP is terminated by the Board or the committee appointed by the Board to administer the 2017 LTIP, or the date all available common units available have been delivered. Common units delivered pursuant to the 2017 LTIP will consist, in whole or part, of (i) common units acquired in the open market, (ii) common units acquired from the Partnership (including newly issued units), any of our affiliates or any other person or (iii) any combination of the foregoing. Employees, consultants and non-employee directors of the Partnership, the General Partner, GP LLC and their affiliates are generally eligible to receive awards under the 2017 LTIP. The 2017 LTIP provides for the issuance of a variety of equity-based grants, including grants of (i) options, (ii) unit appreciation rights, (iii) restricted units, (iv) phantom units, (v) cash awards, (vi) performance awards, (vii) distribution equivalent rights, and (viii) other unit-based awards. The plan is administered by the Compensation, Nominating and Governance Committee of the Board, which determines the terms and conditions of awards granted under the 2017 LTIP. The Partnership recognizes forfeitures for any awards issued under this plan as they occur. Unit-Based Awards Unit-based awards under the 2017 LTIP are generally issued to certain employees and non-employee directors of the Partnership. Awards granted to employees vest at the end of a 3 year period and awards granted to non-employee directors are immediately vested. Directors are given the option to take immediate issuance of the vested awards or defer such issuance until a later date. Upon deferral of issuance, such units will continue to accumulate DERs until issuance. In connection with the phantom unit awards, the Compensation, Nominating and Governance Committee also granted tandem DERs, which entitle the holders to receive distributions equal to the distributions paid on the Partnership’s common units between the date the units are granted and the vesting date. The DERs are payable in cash upon vesting but may be subject to forfeiture if the grantee ceases employment prior to vesting. A summary of activity in the outstanding grants during 2018 is as follows: (In thousands) Common Units Weighted Average Exercise Price Outstanding grants at January 1, 2018 — — Granted 75 29.16 Fully vested and issued (17 ) 31.24 Forfeitures (2 ) 38.28 Outstanding at December 31, 2018 56 29.10 The awards granted in the first quarter of 2018 were valued using the closing price of NRP's units as of the grant date. The grant date fair value of the 2017 LTIP awards granted during the period was $2.2 million , including awards granted to board members with a grant date fair value of $0.6 million which immediately vested and of which $0.4 million were issued. Total unit-based compensation expense recorded in the year ended December 31, 2018 associated with these awards was $1.0 million and $0.1 million included in General and administrative expense and Operating and maintenance expense, respectively, in the Partnership's Consolidated Statements of Comprehensive Income. The unamortized cost associated with unvested outstanding awards as of December 31, 2018 is $1.2 million , which is to be recognized over a weighted average period of 2.1 years .

Supplemental Quarterly Informat

Supplemental Quarterly Information (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Supplemental Quarterly Information (Unaudited)	Quarterly Financial Data The following table summarizes quarterly financial data for 2018: (In thousands, except per unit data) First (1) (2) Second (1) (2) Third (1) Fourth (3) (4) (5) Total Revenues (including affiliates) $ 59,478 $ 69,451 $ 58,207 $ 63,935 $ 251,071 Gain on litigation settlement — — — 25,000 25,000 Gain on asset sales, net 651 168 — 1,622 2,441 Asset impairments 242 — — 18,038 18,280 Income from operations 44,236 52,863 43,346 52,093 192,538 Net income from continuing operations 26,286 35,129 25,853 35,092 122,360 Income (loss) from discontinued operations (1,948 ) 2,981 2,688 13,966 17,687 Net income 24,338 38,110 28,541 49,058 140,047 Net income attributable to NRP 24,338 37,241 28,900 49,058 139,537 Net income attributable to common unitholders and general partner 16,838 29,741 21,400 41,558 109,537 Income from continuing operations per common unit Basic $ 1.50 $ 2.14 $ 1.50 $ 2.21 $ 7.35 Diluted 1.16 1.57 1.18 1.69 5.90 Net income per common unit Basic $ 1.35 $ 2.38 $ 1.71 $ 3.33 $ 8.77 Diluted 1.08 1.71 1.30 2.36 6.76 Weighted average number of common units outstanding (basic) 12,238 12,246 12,246 12,247 12,244 Weighted average number of common units outstanding (diluted) 22,125 21,383 21,840 20,394 20,234 (1) As a result of the sale of its construction aggregates business, the Partnership classified the operating results related to this business as discontinued operations in the Consolidated Statements of Comprehensive Income subsequent to the filing of the Third Quarter 2018 Form 10-Q. See below for a reconciliation to the amounts reported in the Third Quarter 2018 Form 10-Q. (2) During the third quarter of 2018 the Partnership identified an error related to its modified retrospective adoption of ASC 606 on January 1, 2018 for certain coal and aggregates royalty leases and revised its financial statements for the first and second quarter of 2018 in its Third Quarter 2018 Form 10-Q. (3) During the fourth quarter of 2018 the Partnership recorded $25 million in other income related to the Hillsboro litigation settlement. See Note 17. Commitments and Contingencies for more information. (4) During the fourth quarter of 2018 the Partnership sold its construction aggregates business for $205 million , before customary purchase price adjustments and transaction expenses, and recorded a gain of $13.1 million included in Income from discontinued operations on the Partnership's Consolidated Statement of Comprehensive Income. See Note 4. Discontinued Operations for more information. (5) During the fourth quarter of 2018 the Partnership recorded $18.0 million in aggregates and coal property impairment. See Note 11. Mineral Rights, Net for more information. The following tables reconcile the previously reported quarterly information to the quarterly financial data disclosed above: (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised First Quarter 2018 Revenues (including affiliates) $ 86,630 $ (27,152 ) $ 59,478 Gain on asset sales, net 660 (9 ) 651 Asset impairments 242 — 242 Income from operations 42,322 1,914 44,236 Net income from continuing operations 24,352 1,934 26,286 Net loss from discontinued operations (14 ) (1,934 ) (1,948 ) Net income 24,338 — 24,338 Net income attributable to NRP 24,338 — 24,338 Net income attributable to common unitholders and general partner 16,838 — 16,838 Income from continuing operations per common unit Basic $ 1.35 $ 0.15 $ 1.50 Diluted 1.08 0.09 1.16 Net income per common unit Basic $ 1.35 $ — $ 1.35 Diluted 1.08 — 1.08 Weighted average number of common units outstanding (basic) 12,238 — 12,238 Weighted average number of common units outstanding (diluted) 22,125 — 22,125 Second Quarter 2018 Revenues (including affiliates) $ 109,860 $ (40,409 ) $ 69,451 Gain on asset sales, net 210 (42 ) 168 Income from operations 55,878 (3,015 ) 52,863 Net income from continuing operations 38,144 (3,015 ) 35,129 Net income (loss) from discontinued operations (34 ) 3,015 2,981 Net income 38,110 — 38,110 Net income attributable to NRP 37,241 — 37,241 Net income attributable to common unitholders and general partner 29,741 — 29,741 Income from continuing operations per common unit Basic $ 2.38 $ (0.24 ) $ 2.14 Diluted 1.71 (0.14 ) 1.57 Net income per common unit Basic $ 2.38 $ — $ 2.38 Diluted 1.71 — 1.71 Weighted average number of common units outstanding (basic) 12,246 — 12,246 Weighted average number of common units outstanding (diluted) 21,383 — 21,383 (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised Third Quarter 2018 Revenues (including affiliates) $ 94,855 $ (36,648 ) $ 58,207 Gain on asset sales, net 163 (163 ) — Income from operations 46,066 (2,720 ) 43,346 Net income from continuing operations 28,565 (2,712 ) 25,853 Net income (loss) from discontinued operations (24 ) 2,712 2,688 Net income 28,541 — 28,541 Net income attributable to NRP 28,900 — 28,900 Net income attributable to common unitholders and general partner 21,400 — 21,400 Income from continuing operations per common unit Basic $ 1.71 $ (0.22 ) $ 1.50 Diluted 1.30 (0.12 ) 1.18 Net income per common unit Basic $ 1.71 $ — $ 1.71 Diluted 1.30 — 1.30 Weighted average number of common units outstanding (basic) 12,246 — 12,246 Weighted average number of common units outstanding (diluted) 21,840 — 21,840 The following table summarizes quarterly financial data for 2017: (In thousands, except per unit data) First (1) (2) Second (1) (3) Third (1) Fourth (1) Total (1) Revenues (including affiliates) $ 61,432 $ 58,015 $ 58,406 $ 64,927 $ 242,780 Gain on asset sales, net 29 3,184 154 178 3,545 Asset impairments 1,778 — — 1,189 2,967 Income from operations 38,124 47,522 43,052 47,861 176,559 Debt modification expense 7,807 132 — — 7,939 Loss on extinguishment of debt — 4,107 — — 4,107 Net income from continuing operations 7,588 23,153 23,079 28,665 82,485 Net income (loss) from discontinued operations (1,684 ) 2,837 2,987 2,042 6,182 Net income 5,904 25,990 26,066 30,707 88,667 Net income attributable to common unitholders and general partner 3,404 18,452 18,416 22,942 63,214 Income from continuing operations per common unit Basic $ 0.41 $ 1.25 $ 1.24 $ 1.67 $ 4.57 Diluted 0.50 1.01 0.94 1.18 3.68 Net income per common unit Basic $ 0.28 $ 1.47 $ 1.48 $ 1.84 $ 5.06 Diluted 0.28 1.13 1.07 1.26 3.96 Weighted average number of common units outstanding (basic) 12,232 12,232 12,232 12,232 12,232 Weighted average number of common units outstanding (diluted) 14,945 22,459 23,980 23,874 21,950 (1) As a result of the sale of its construction aggregates business, the Partnership classified the operating results related to this business as discontinued operations in the Consolidated Statements of Comprehensive Income subsequent to the filing of the 2017 Form 10-K. See below for a reconciliation to the amounts reported in the 2017 Form 10-K. (2) During the first quarter of 2017 the Partnership incurred $7.8 million of debt modification costs as a result of the exchange of $241 million of our 2018 Senior Notes for 2022 Senior Notes. (3) During the second quarter of 2017 the Partnership incurred a $4.1 million loss on extinguishment of debt related to the 4.563% premium paid to redeem the 2018 Senior Notes in April 2017. The following tables reconcile the previously reported quarterly information to the quarterly financial data disclosed above: (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised First Quarter 2017 Revenues (including affiliates) $ 88,653 $ (27,221 ) $ 61,432 Gain on asset sales, net 44 (15 ) 29 Asset impairments 1,778 — 1,778 Income from operations 37,042 1,082 38,124 Debt modification expense 7,807 — 7,807 Net income from continuing operations 6,111 1,477 7,588 Net income (loss) from discontinued operations (207 ) (1,477 ) (1,684 ) Net income 5,904 — 5,904 Net income attributable to common unitholders and general partner 3,404 — 3,404 Income from continuing operations per common unit Basic $ 0.30 $ 0.12 $ 0.41 Diluted 0.30 0.10 0.50 Net income per common unit Basic $ 0.28 $ — $ 0.28 Diluted 0.28 — 0.28 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 14,945 — 14,945 Second Quarter 2017 Revenues (including affiliates) $ 91,570 $ (33,555 ) $ 58,015 Gain on asset sales, net 3,361 (177 ) 3,184 Income from operations 50,404 (2,882 ) 47,522 Debt modification expense 132 — 132 Loss on extinguishment of debt 4,107 — 4,107 Net income from continuing operations 25,857 (2,704 ) 23,153 Net income (loss) from discontinued operations 133 2,704 2,837 Net income 25,990 — 25,990 Net income attributable to common unitholders and general partner 18,452 — 18,452 Income from continuing operations per common unit Basic $ 1.46 $ (0.22 ) $ 1.25 Diluted 1.13 (0.12 ) 1.01 Net income per common unit Basic $ 1.47 $ — $ 1.47 Diluted 1.13 — 1.13 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 22,459 — 22,459 (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised Third Quarter 2017 Revenues (including affiliates) $ 93,116 $ (34,710 ) $ 58,406 Gain on asset sales, net 171 (17 ) 154 Income from operations 46,531 (3,479 ) 43,052 Net income from continuing operations 26,499 (3,420 ) 23,079 Net income (loss) from discontinued operations (433 ) 3,420 2,987 Net income 26,066 — 26,066 Net income attributable to common unitholders and general partner 18,416 — 18,416 Income from continuing operations per common unit Basic $ 1.51 $ (0.27 ) $ 1.24 Diluted 1.08 (0.14 ) 0.94 Net income per common unit Basic $ 1.48 $ — $ 1.48 Diluted 1.07 — 1.07 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 23,980 — 23,980 Fourth Quarter 2017 Revenues (including affiliates) $ 100,822 $ (35,895 ) $ 64,927 Gain on asset sales, net 280 (102 ) 178 Asset impairments 1,253 (64 ) 1,189 Income from operations 49,998 (2,137 ) 47,861 Net income from continuing operations 30,741 (2,076 ) 28,665 Net income (loss) from discontinued operations (34 ) 2,076 2,042 Net income 30,707 — 30,707 Net income attributable to common unitholders and general partner 22,942 — 22,942 Income from continuing operations per common unit Basic $ 1.84 $ (0.17 ) $ 1.67 Diluted 1.26 (0.09 ) 1.18 Net income per common unit Basic $ 1.84 $ — $ 1.84 Diluted 1.26 — 1.26 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 23,874 — 23,874 (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised Total 2017 Revenues (including affiliates) $ 374,161 $ (131,381 ) $ 242,780 Gain on asset sales, net 3,856 (311 ) 3,545 Asset impairments 3,031 (64 ) 2,967 Income from operations 183,975 (7,416 ) 176,559 Debt modification expense 7,939 — 7,939 Loss on extinguishment of debt 4,107 — 4,107 Net income from continuing operations 89,208 (6,723 ) 82,485 Net income (loss) from discontinued operations (541 ) 6,723 6,182 Net income 88,667 — 88,667 Net income attributable to common unitholders and general partner 63,214 — 63,214 Income from continuing operations per common unit — Basic $ 5.11 $ (0.54 ) $ 4.57 Diluted 3.98 (0.30 ) 3.68 Net income per common unit Basic $ 5.06 $ — $ 5.06 Diluted 3.96 — 3.96 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 21,950 — 21,950

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Consolidated Financial Statements of the Partnership have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP"). The consolidated financial statements include the accounts of Natural Resource Partners L.P. and its wholly owned subsidiaries, as well as BRP LLC ("BRP"), a joint venture with International Paper Company controlled by the Partnership. The Partnership has an equity investment in Ciner Wyoming through which it is able to exercise significant influence over but does not control the investee and is not the primary beneficiary of the investee’s activities and is accounted for using the equity method. Intercompany transactions and balances have been eliminated. Certain reclassifications have been made to prior year amounts on the Consolidated Statements of Comprehensive Income and Consolidated Statements of Cash Flows to conform with current year presentation. These reclassifications have no impact on previously reported net income or total cash flows from operating, investing or financing activities.
Use of Estimates	Use of Estimates Preparation of the accompanying financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities in the accompanying Consolidated Balance Sheets, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses in the accompanying Consolidated Statements of Comprehensive Income during the reporting period. Actual results could differ from those estimates. The most significant estimates pertain to coal and aggregates reserves and related cash flow estimates which are used to compute depreciation, depletion and amortization and impairments of coal and aggregates properties and commitments and contingencies.
Fair Value	Fair Value The Partnership discloses certain assets and liabilities using fair value as defined by authoritative guidance. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. See Note 14. Fair Value Measurements for further details. There are three levels of inputs that may be used to measure fair value: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial assets and liabilities whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation.
Cash and Cash Equivalents	Cash, Cash Equivalents and Restricted Cash The Partnership considers all highly liquid short-term investments with an original maturity of three months or less to be cash equivalents. Restricted cash at December 31, 2018 included cash proceeds received from the sale of the Partnership's construction aggregates business required to be used to repay debt, make acquisitions or make capital expenditures per the terms of its and Opco's debt agreements, as defined in Note 13. Debt, Net . NRP intends to use these proceeds to repay debt.
Accounts Receivable	Allowance for Doubtful Accounts The Partnership records an allowance for doubtful accounts for its accounts receivables and notes receivables which it determines to be uncollectible based on the specific identification method. Receivables are written off when collection efforts are exhausted and future recovery is doubtful.
Plant and Equipment	Plant and Equipment Plant and equipment is recorded at its original cost of construction or, upon acquisition, at fair value of the asset acquired and consists of coal preparation plants, related coal handling facilities, and other coal and aggregates transportation and processing infrastructure. Expenditures for new facilities or that substantially increase the useful life of property are capitalized and reported in the Consolidated Statements of Cash Flows as an investing activity. These assets are depreciated on a straight-line basis over their useful lives generally as follows: Years Buildings and improvements 20 to 40 Machinery and equipment 5 to 12 Leasehold improvements Life of Lease
Mineral Rights	Mineral Rights Mineral rights owned and leased are recorded at its original cost of construction or, upon acquisition, at fair value of the assets acquired. Coal and aggregates mineral rights are depleted on a unit-of-production basis by lease, based upon minerals mined in relation to the net cost of the mineral properties and estimated proven and probable tonnage therein.
Intangible Assets	Intangible Assets The Partnership’s intangible assets consist primarily of contracts that at acquisition were more favorable for the Partnership than prevailing market rates, known as above-market contracts. Management expects for the above-market rates to be received until the reserves are exhausted on its above-market contracts, which includes additional renewal terms of the respective leases. The estimated fair values of the above-market rate contracts are determined based on the present value of future cash flow projections related to the underlying assets acquired. Intangible assets are amortized on a unit-of-production basis.
Asset Impairment	Asset Impairment The Partnership has developed procedures to evaluate its long-lived assets for possible impairment periodically or whenever events or changes in circumstances indicate an asset's carrying amount may not be recoverable. Potential events or circumstances include, but are not limited to, specific events such as a reduction in economically recoverable reserves or production ceasing on a property for an extended period. This analysis is based on historic, current and future performance and considers both quantitative and qualitative information. A long-lived asset is deemed impaired when the future expected undiscounted cash flows from its use and disposition is less than the assets’ carrying value. Impairment is measured based on the estimated fair value, which is usually determined based upon the present value of the projected future cash flow compared to the assets’ carrying value. The Partnership believes its estimates of cash flows and discount rates are consistent with those of principal market participants. The Partnership evaluates its equity investment for impairment when events or changes in circumstances indicate, in management’s judgment, that the carrying value of such investment may have experienced an other-than-temporary decline in value. When evidence of loss in value has occurred, management compares the estimated fair value of the investment to the carrying value of the investment to determine whether potential impairment has occurred. If the estimated fair value is less than the carrying value and management considers the decline in value to be other than temporary, the excess of the carrying value over the estimated fair value is recognized in the financial statements as an impairment loss. The fair value of the impaired investment is based on quoted market prices (Level 1), or upon the present value of expected cash flows using discount rates believed to be consistent with those used by principal market participants (Level 3), plus market analysis of comparable assets owned by the investee, if appropriate.
Revenue Recognition	Revenue Recognition Coal Royalty and Other Segment Revenues Royalty-based leases. Approximately two-thirds of the Partnership's royalty-based leases have initial terms of five to 40 years, with substantially all lessees having the option to extend the lease for additional terms. For these types of leases, the lessees generally make payments to NRP based on the greater of a percentage of the gross sales price or a fixed price per ton of mineral they mine or sell. Most of NRP’s coal and aggregates royalty leases require the lessee to pay quarterly or annual minimum amounts, either made in advance or arrears, which are generally recoupable through actual royalty production over certain time periods that generally range from three to five years. In accordance with previous accounting standards in effect prior to January 1, 2018, NRP recognized all coal and aggregates royalty revenue over the lease term based on production. The recognition of revenue from minimum payments was deferred until either recoupment through royalty production occurred or when the recoupment period expired for unrecouped minimums. Under the new revenue recognition standard, management has defined NRP's coal and aggregates royalty lease performance obligation as providing the lessee the right to mine and sell NRP's coal or aggregates over the lease term. The Partnership then evaluated the likelihood that consideration NRP expected to receive from its lessees resulting from production would exceed consideration expected to be received from minimum payments over the lease term. As a result of this evaluation, revenue recognition from the Partnership's royalty-based leases is based on either production or minimum payments as follows: • Production Leases : Leases for which the Partnership expects that consideration from production will be greater than consideration from minimums over the lease term. Revenue recognition for these leases is recognized over time based on production as Coal royalty revenue or Aggregates royalty revenue, as applicable. Deferred revenue from minimums is recognized as royalty revenue when recoupment occurs or as Production lease minimum revenue when the recoupment period expires. In addition, NRP recognizes breakage revenue from minimums when NRP determines that recoupment is remote. This breakage revenue is included in Production lease minimum revenue. • Minimum Leases : Leases for which the Partnership expects that consideration from minimums will be greater than consideration from production over the lease term. Revenue recognition for these leases is recognized straight-line over the lease term based on the minimum consideration amount as Minimum lease straight-line revenue. This evaluation is performed at the inception of the lease and only reassessed upon modification or renewal of the lease. Oil and gas related revenues consist of revenues from royalties and overriding royalties and are recognized on the basis of volume of hydrocarbons sold by lessees and the corresponding revenue from those sales. Also, included within oil and gas royalties are lease bonus payments, which are generally paid upon the execution of a lease. The Partnership also has overriding royalty revenue interests in coal reserves. Revenue from these interests is recognized over time based on when the coal is sold. Wheelage. Revenue related to fees collected per ton to transport foreign coal across property owned by the Partnership that is recognized over time as transportation across the property occurs. Other revenue. Other revenue consists primarily of rental payments and surface damage fees related to certain land owned by the Partnership and is recognized straight-line over time as it is earned. Other revenues also include property tax revenues. The majority of property taxes paid on the Partnership's properties are reimbursable by the lessee and are recognized on a gross basis over time which reflects the reimbursement of property taxes by the lessee. Property taxes paid by NRP are included in Operating and maintenance expenses on the Partnership's Consolidated Statements of Comprehensive Income. Transportation and processing services revenue. The Partnership owns transportation and processing infrastructure that is leased to third parties for throughput fees. Revenue is recognized over time based on the coal tons transported over the beltlines or processed through the facilities. Contract modifications Contract modifications that impact goods or services or the transaction price are evaluated in accordance with ASC 606. A majority of the Partnership's contract modifications pertain to its coal and aggregates royalty contracts and include, but are not limited to, extending the lease term, changes to royalty rates, floor prices or minimum consideration, assignment of the contract, forfeiture of recoupment rights or termination due to the exhaustion of merchantable and mineable reserves. Consideration received in conjunction with a modification of an ongoing lease will be deferred and recognized straight-line over the remaining term of the contract. Consideration received to assign a lease to another party and related forfeited minimums will be recognized immediately upon the termination of the contract. Fees from contract modifications are recognized in Lease modification fees within Coal royalty and other revenues on our Consolidated Statements of Comprehensive Income while modifications in royalty rates and minimums will be recognized prospectively in accordance with the above lease classification. In accordance with the transition guidance in paragraph 606-10-65-1, revenues from contracts that were modified before January 1, 2018 were not retrospectively restated for those modifications and instead reflected the aggregate effect of those modifications when identifying the satisfied and unsatisfied performance obligations, determining the transaction price and allocating the transaction price to the satisfied and unsatisfied performance obligation. Contract Assets and Liabilities from Contracts with Customers Contract assets include receivables from contracts with customers and are recorded when the right to consideration becomes unconditional. Receivables are recognized when the minimums are contractually owed, production occurs or minimums accrued for based on the passage of time. Contract liabilities represent minimum consideration received, contractually owed or earned based on the passage of time. The current portion of deferred revenue relates to deferred revenue on minimum leases and lease modification fees that are to be recognized as revenue on a straight-line basis over the next twelve months. The long-term portion of deferred revenue relates to deferred revenue on production leases and lease modification fees that are to be recognized as revenue on a straight-line basis beyond the next twelve months. Due to uncertainty in the amount of deferred revenue that will be recouped and recognized as Coal royalty revenue from its production leases over the next twelve months, the Partnership is unable to estimate the current portion of deferred revenue. See "—Recently Adopted Accounting Standards—Revenue Recognition" below for information regarding the impact of adopting the new revenue recognition standard in January 2018. Equity in Earnings from Ciner Wyoming The Partnership accounts for non-marketable equity investments using the equity method of accounting if the investment gives it the ability to exercise significant influence over, but not control of, an investee. The Partnership's 49% investment in Ciner Wyoming is accounted for using this method. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and the proportionate share of earnings or losses and distributions. The basis difference between the investment and the proportional share of investee's net assets is attributed to net tangible assets and is amortized over its estimated useful life. The carrying value in Ciner Wyoming is recognized in Equity in unconsolidated investment in the Partnership's Consolidated Balance Sheets. The Partnership's adjusted share of the earnings or losses of Ciner Wyoming and amortization of the basis difference is recognized in Equity in earnings of Ciner Wyoming in the Consolidated Statements of Comprehensive Income. The Partnership increases its investment for its proportional share of distributions received from Ciner Wyoming. These cash flows are reported utilizing the cumulative earnings approach. Under this approach, distributions received are considered returns on investment and classified as operating cash inflows unless the cumulative distributions received exceed the Partnership's cumulative equity in earnings. The excess of cumulative distributions received over the Partnership's cumulative equity in earnings are considered returns of investment and classified as investing cash inflows.
Property Taxes	Property Taxes The Partnership is responsible for paying property taxes on the properties it owns. Typically, the lessees are contractually responsible for reimbursing the Partnership for property taxes on the leased properties. The payment of and reimbursement of property taxes is included in Operating and maintenance expenses and in Coal royalty and other revenues, respectively, in the Consolidated Statements of Comprehensive Income.
Transportation Revenue and Expense	Transportation Revenue and Expense The Partnership records transportation revenue and pays transportation costs to a Foresight Energy LP ("Foresight Energy") affiliate to operate equipment on behalf of the Partnership. The revenue and expenses related to these transactions are recorded as Transportation and processing services (or Transportation and processing services—affiliates) and Operating and maintenance expenses or (Operating and maintenance expenses—affiliates), respectively, in the Consolidated Statements of Comprehensive Income. Subsequent to May 9, 2017, Foresight Energy is no longer deemed a related party. Refer to Note 15. Related Party Transactions for further details.
Unit-Based Compensation	Unit-Based Compensation The Partnership has awarded unit-based compensation in the form of equity-based awards and phantom units. Compensation cost is measured at the grant date for equity-classified awards and remeasured each reporting period for liability-classified awards based on the fair value of an award and is recognized over the service period, which is generally the vesting period. Forfeitures are recognized as they occur. Unit-based compensation expense for all awards is recognized in General and administrative expense and Operating and maintenance expense in the Consolidated Statements of Comprehensive Income.
Deferred Financing Costs	Deferred Financing Costs Deferred financing costs consist of legal and other costs related to the issuance of the Partnership’s debt. These costs are amortized over the term of the respective line-of-credit or debt arrangements. Deferred financing costs related to the Partnership's revolving credit facility are included in Other assets (long-term) on the Partnership's Consolidated Balance Sheets. Deferred financing costs related to the Partnership's note agreements are included as a direct deduction from the carrying amount of the debt liability in Current portion of long-term debt, net or Long-term debt, net on the Partnership's Consolidated Balance Sheets.
Income Taxes	Income Taxes The Partnership is not subject to federal or material state income taxes, as the unitholders are taxed individually on their allocable share of taxable income. Net income for financial statement purposes may differ significantly from taxable income reportable to unitholders as a result of differences between the tax basis and financial reporting basis of assets and liabilities. In the event of an examination of the Partnership’s tax return, the tax liability of the unitholders could be changed if an adjustment in the Partnership’s income is ultimately sustained by the taxing authorities.
Recently Issued Accounting Standards	Recently Adopted Accounting Standards Revenue Recognition On January 1, 2018, NRP adopted Accounting Standards Codification (ASC) 606, Revenue from Contracts with Customers, and all the related amendments (the “new revenue standard” and "ASC 606") to all open contracts using the modified retrospective method. The adoption of the new revenue standard impacted royalty revenue from NRP's coal and aggregates royalty leases as further described below. NRP recognized a $70.5 million cumulative effect of adoption adjustment in the opening balance of partners' capital on January 1, 2018. Prior year information has not been restated and continues to be reported under the accounting standards in effect for those periods. The new revenue standard had no impact on revenues from NRP's Soda Ash operating segment or on the discontinued operations. A majority of NRP’s coal and aggregates royalty revenue continues to be recognized over the lease term based on production. For coal and aggregates royalty leases for which NRP expects consideration from minimum payments to be greater than consideration from production over the lease term, royalty revenue is now recognized straight-line over the lease term based on the minimum payment consideration. The cumulative effects of the changes made to the Partnership's Consolidated Balance Sheet at January 1, 2018 for the adoption of the new revenue standard were as follows: (In thousands) Balance at December 31, 2017 Adjustments due to ASC 606 Balance at January 1, 2018 Assets Accounts receivable, net (including affiliates) $ 24,211 $ 4,875 $ 29,086 Liabilities Current portion of deferred revenue $ — $ 1,022 $ 1,022 Deferred revenue 100,605 (66,613 ) 33,992 Partners’ capital Common unitholders’ interest $ 199,851 $ 69,057 $ 268,908 General partner’s interest 1,857 1,409 3,266 Total partners’ capital 265,211 70,466 335,677 The impact of adoption of the new revenue standard on NRP’s Consolidated Balance Sheet and Consolidated Statement of Comprehensive Income was as follows: As of December 31, 2018 (In thousands) As Reported Balances without Adoption of ASC 606 Effect of Change Assets Accounts receivable, net (including affiliates) $ 32,058 $ 27,520 $ 4,538 Total assets 1,341,647 1,337,109 4,538 Liabilities and capital Current portion of deferred revenue $ 3,509 $ — $ 3,509 Deferred revenue 49,044 62,783 (13,739 ) Total liabilities 756,514 766,744 (10,230 ) Partners’ capital Common unitholders’ interest $ 355,113 $ 340,640 $ 14,473 General partner’s interest 5,014 4,719 295 Total partners’ capital 423,481 408,713 14,768 Total liabilities and capital 1,341,647 1,337,109 4,538 For the Year Ended December 31, 2018 (In thousands, except per unit data) As Reported Amounts without Adoption of ASC 606 Effect of Change Coal royalty and other revenues (including affiliates) (1) $ 178,878 $ 234,428 $ (55,550 ) Net income from continuing operations 122,360 178,058 (55,698 ) Net income 140,047 195,745 (55,698 ) Net income per common unit (basic) 8.77 13.23 (4.46 ) Net income per common unit (diluted) 6.76 9.46 (2.70 ) (1) The total effect of adopting ASC 606 was $55.6 million during the year ended December 31, 2018, which included $33.4 million related to the forfeiture of recoupable balances in connection with the fourth quarter 2018 settlement of the Macoupin and Hillsboro lawsuits, the majority of which was previously recognized in partners' capital upon adoption and $7.2 million of modification fees and forfeited recoupable balances related to fourth quarter 2018 lease modifications which were deferred under ASC 606 and will be recognized straight-line over the respective modified lease terms. Recently Issued Accounting Standards Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The new standard requires a lessee to recognize assets and liabilities on the balance sheet for the present value of the rights and obligations created by all leases with terms of more than 12 months. This standard does not apply to leases that explore for or use minerals, oil, natural gas and similar non-regenerative resources, including the intangible right to explore for those natural resources and rights to use the land in which those natural resources are contained. The guidance also requires disclosures designed to give financial statement users information on the amount, timing and uncertainty of cash flows arising from leases. The guidance is effective for annual and interim periods beginning after December 15, 2018 and is to be adopted using a modified retrospective approach. The Partnership will adopt this standard effective January 1, 2019 and does not expect that the provisions of this guidance will have a material impact on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Plant and Equipment Useful Lives	These assets are depreciated on a straight-line basis over their useful lives generally as follows: Years Buildings and improvements 20 to 40 Machinery and equipment 5 to 12 Leasehold improvements Life of Lease
Schedule of New Accounting Pronouncements	The cumulative effects of the changes made to the Partnership's Consolidated Balance Sheet at January 1, 2018 for the adoption of the new revenue standard were as follows: (In thousands) Balance at December 31, 2017 Adjustments due to ASC 606 Balance at January 1, 2018 Assets Accounts receivable, net (including affiliates) $ 24,211 $ 4,875 $ 29,086 Liabilities Current portion of deferred revenue $ — $ 1,022 $ 1,022 Deferred revenue 100,605 (66,613 ) 33,992 Partners’ capital Common unitholders’ interest $ 199,851 $ 69,057 $ 268,908 General partner’s interest 1,857 1,409 3,266 Total partners’ capital 265,211 70,466 335,677 The impact of adoption of the new revenue standard on NRP’s Consolidated Balance Sheet and Consolidated Statement of Comprehensive Income was as follows: As of December 31, 2018 (In thousands) As Reported Balances without Adoption of ASC 606 Effect of Change Assets Accounts receivable, net (including affiliates) $ 32,058 $ 27,520 $ 4,538 Total assets 1,341,647 1,337,109 4,538 Liabilities and capital Current portion of deferred revenue $ 3,509 $ — $ 3,509 Deferred revenue 49,044 62,783 (13,739 ) Total liabilities 756,514 766,744 (10,230 ) Partners’ capital Common unitholders’ interest $ 355,113 $ 340,640 $ 14,473 General partner’s interest 5,014 4,719 295 Total partners’ capital 423,481 408,713 14,768 Total liabilities and capital 1,341,647 1,337,109 4,538 For the Year Ended December 31, 2018 (In thousands, except per unit data) As Reported Amounts without Adoption of ASC 606 Effect of Change Coal royalty and other revenues (including affiliates) (1) $ 178,878 $ 234,428 $ (55,550 ) Net income from continuing operations 122,360 178,058 (55,698 ) Net income 140,047 195,745 (55,698 ) Net income per common unit (basic) 8.77 13.23 (4.46 ) Net income per common unit (diluted) 6.76 9.46 (2.70 ) (1) The total effect of adopting ASC 606 was $55.6 million during the year ended December 31, 2018, which included $33.4 million related to the forfeiture of recoupable balances in connection with the fourth quarter 2018 settlement of the Macoupin and Hillsboro lawsuits, the majority of which was previously recognized in partners' capital upon adoption and $7.2 million of modification fees and forfeited recoupable balances related to fourth quarter 2018 lease modifications which were deferred under ASC 606 and will be recognized straight-line over the respective modified lease terms.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table represents the Partnership's Coal Royalty and Other segment revenues (including affiliates) by major source: Year Ended (In thousands) December 31, 2018 Coal royalty revenue $ 129,341 Production lease minimum revenue 8,207 Minimum lease straight-line revenue 2,362 Property tax revenue 5,422 Wheelage revenue 6,484 Coal overriding royalty revenue 13,878 Aggregates royalty revenue 4,739 Oil and gas royalty revenue 6,608 Other revenue 1,837 Coal royalty and other revenues (1) $ 178,878 Transportation and processing services revenue (2) 23,887 Total Coal royalty and other segment revenues $ 202,765 (1) Represents revenue from contracts with customers as defined under ASC 606. (2) Revenue from contracts with customers as defined under ASC 606 was $13.2 million for the year ended December 31, 2018 . The remaining transportation and processing services revenue of $10.7 million for the year ended December 31, 2018 was related to other NRP-owned infrastructure leased to and operated by third party operators accounted for under ASC 840, Leases.
Contract with Customer, Asset and Liability	The following table details the Partnership's Coal Royalty and Other segment receivables and liabilities resulting from contracts with customers: December 31, January 1, (In thousands) 2018 2018 Receivables Total accounts receivable, net (including affiliates) (1) $ 29,001 $ 25,443 Prepaid expenses and other (2) 2,483 2,830 Contract liabilities Current portion of deferred revenue $ 3,509 $ 1,022 Deferred revenue 49,044 33,992 (1) Included in this amount is $4.4 million and $ 1.9 million of accounts receivable related to accrued minimum consideration as of December 31, 2018 and January 1, 2018, respectively. (2) Notes receivable from contracts with customers are included within Prepaid expenses and other in the Consolidated Balance Sheets.
Revenue Recognition Deferred Revenue Rollforward	The following table shows the activity related to the Partnership's Coal Royalty and Other segment deferred revenue: Year Ended (In thousands) December 31, 2018 Balance at December 31, 2017 $ 100,605 Cumulative adjustment for change in accounting principle (1) (65,591 ) Balance at January 1, 2018 (current and non-current) $ 35,014 Recognition of previously deferred revenue (20,242 ) Accrued minimum payments and lease modification fees due 5,592 Cash received for minimum payments and lease modification fees 32,189 Balance at December 31, 2018 (current and non-current) (2) $ 52,553 (1) Included in this amount is $(67.5) million recognized in Partners' capital and $1.9 million of accrued minimum consideration recognized in Accounts receivable, net. (2) Included in this amount is $7.2 million of deferred modification fees and forfeited recoupable balances which will be recognized straight-line over the respective modified lease terms in Coal Royalty and other revenues on the Consolidated Statements of Comprehensive Income over the remaining terms of the modified leases, which extend over the next 6 years . The following table shows the Partnership's Coal Royalty and Other segment revenue recognized during the year ended December 31, 2018 that was included in the deferred revenue balance at the beginning of the period: Year Ended (In thousands) December 31, 2018 Production leases - revenue impact Recoupments recognized in Coal and aggregates royalty revenue $ 10,178 Breakage revenue recognized in Production lease minimum revenue 7,169 Expiration of unrecouped minimums recognized in Production lease minimum revenue 935 Minimum leases - revenue impact Minimum lease amortization recognized in Minimum lease straight-line revenue 1,960 Total previously deferred revenue recognized $ 20,242
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The Partnership's non-cancelable annual minimum payments due under the lease terms of its coal and aggregates royalty leases are as follows: Lease Term (1) Weighted Average Remaining Years as of December 31, 2018 Annual Minimum Payments (In thousands) 1 - 5 years 0.6 $ 13,072 5 - 10 years 1.3 13,060 10+ years 9.0 41,202

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations	The following tables present the carrying amounts of the Partnership's assets and liabilities of discontinued operations in the Consolidated Balance Sheets: December 31, 2018 (In thousands) Construction Aggregates NRP Total ASSETS Current assets: Accounts receivable, net $ 5 $ 988 $ 993 Total assets of discontinued operations $ 5 $ 988 $ 993 LIABILITIES Current liabilities: Accounts payable (including affiliates) $ 181 $ — $ 181 Accrued liabilities 766 — 766 Total liabilities of discontinued operations $ 947 $ — $ 947 December 31, 2017 (In thousands) Construction Aggregates NRP Total ASSETS Current assets: Cash and cash equivalents $ 2,847 $ — $ 2,847 Accounts receivable, net 22,976 991 23,967 Inventory 7,553 — 7,553 Prepaid expenses and other 2,056 — 2,056 Total current assets of discontinued operations 35,432 991 36,423 Land 1,239 — 1,239 Plant and equipment, net 44,822 — 44,822 Mineral rights, net 105,466 — 105,466 Intangible assets, net 2,734 — 2,734 Other assets 1,681 — 1,681 Total assets of discontinued operations $ 191,374 $ 991 $ 192,365 LIABILITIES Current liabilities: Accounts payable (including affiliates) (1) $ 6,019 $ — $ 6,019 Accrued liabilities 5,348 — 5,348 Other — 401 401 Total current liabilities of discontinued operations 11,367 401 11,768 Other non-current liabilities 2,220 — 2,220 Total liabilities of discontinued operations $ 13,587 $ 401 $ 13,988 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party liabilities. The following tables present summarized financial results of the Partnership's discontinued operations in the Consolidated Statements of Comprehensive Income: For the Year Ended December 31, 2018 (In thousands) Construction Aggregates NRP Oil and Gas Total Revenues and other income: Construction aggregates $ 116,066 $ — $ 116,066 Road construction and asphalt paving services 18,400 — 18,400 Oil and gas — (3 ) (3 ) Gain on asset sales, net 13,414 — 13,414 Total revenues and other income $ 147,880 $ (3 ) $ 147,877 Operating expenses: Operating and maintenance expenses (including affiliates) (1) $ 117,568 $ 134 $ 117,702 Depreciation, depletion and amortization 12,218 — 12,218 Asset impairments 232 — 232 Total operating expenses $ 130,018 $ 134 $ 130,152 Interest expense, net (38 ) — (38 ) Income (loss) from discontinued operations $ 17,824 $ (137 ) $ 17,687 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party expenses. For the Year Ended December 31, 2017 (In thousands) Construction Aggregates NRP Oil and Gas Total Revenues and other income: Construction aggregates $ 112,970 $ — $ 112,970 Road construction and asphalt paving services 18,411 — 18,411 Oil and gas — 38 38 Gain (loss) on asset sales 311 (289 ) 22 Total revenues and other income $ 131,692 $ (251 ) $ 131,441 Operating expenses: Operating and maintenance expenses (including affiliates) (1) $ 111,633 $ 290 $ 111,923 Depreciation, depletion and amortization 12,579 — 12,579 Asset impairments 64 — 64 Total operating expenses $ 124,276 $ 290 $ 124,566 Interest expense, net (693 ) — (693 ) Income (loss) from discontinued operations $ 6,723 $ (541 ) $ 6,182 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party expenses. For the Year Ended December 31, 2016 (In thousands) Construction Aggregates NRP Oil and Gas Total Revenues and other income: Construction aggregates $ 103,755 $ — $ 103,755 Road construction and asphalt paving services 17,047 — 17,047 Oil and gas — 16,486 16,486 Gain on asset sales, net 13 8,274 8,287 Total revenues and other income $ 120,815 $ 24,760 $ 145,575 Operating expenses: Operating and maintenance expenses (including affiliates) (1) $ 100,656 $ 11,503 $ 112,159 Depreciation, depletion and amortization 14,506 7,527 22,033 Asset impairments 1,065 564 1,629 Total operating expenses $ 116,227 $ 19,594 $ 135,821 Interest expense, net — (3,488 ) (3,488 ) Income from discontinued operations $ 4,588 $ 1,678 $ 6,266 (1) See Note 15. Related Party Transactions for additional information on the Partnership's related party expenses. The following table presents supplemental cash flow information of the Partnership's discontinued operations: Year Ended December 31, (In thousands) 2018 2017 2016 Cash paid for interest $ — $ — $ 1,906 Plant, equipment and mineral rights funded with accounts payable or accrued liabilities 881 294 —

Class A Convertible Preferred_2

Class A Convertible Preferred Units and Warrants (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Preferred Units and Warrants Issued	The Preferred Units and Warrants were initially recognized as follows: (In thousands) March 2, 2017 Transaction price, gross $ 250,000 Structuring, origination and other fees to Preferred Purchasers (7,900 ) Transaction costs to other third parties (10,697 ) Transaction price, net $ 231,403 Allocation of net transaction price Preferred Units, net $ 164,587 Warrant holders interest, net 66,816 Transaction price, net $ 231,403
Financial Position of Preferred Units	Activity related to the Preferred Units is as follows: (In thousands, except unit data) Units Outstanding Financial Position Balance at December 31, 2016 — $ — Issuance of Preferred Units, net 250,000 164,587 Distribution paid-in-kind 8,844 8,844 Balance at December 31, 2017 258,844 $ 173,431 Redemption of PIK Units (8,844 ) (8,844 ) Balance at December 31, 2018 250,000 $ 164,587

Common and Preferred Unit Dis_2

Common and Preferred Unit Distributions (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Schedule of distributions paid	The following table shows the distributions declared and paid to common unitholders during the years ended December 31, 2018 , 2017 and 2016 , respectively: Total Distributions (in thousands) Date Paid Period Covered by Distribution Distribution per Common Unit Common Units GP Interest Total 2018 February 14, 2018 October 1 - December 31, 2017 $ 0.45 $ 5,505 $ 112 $ 5,617 May 14, 2018 January 1 - March 31, 2018 0.45 5,510 113 5,623 August 14, 2018 April 1 - June 30, 2018 0.45 5,511 112 5,623 November 14, 2018 July 1 - September 30, 2018 0.45 5,510 113 5,623 2017 February 14, 2017 October 1 - December 31, 2016 $ 0.45 $ 5,503 $ 112 $ 5,615 May 12, 2017 January 1 - March 31, 2017 0.45 5,506 113 5,619 August 14, 2017 April 1 - June 30, 2017 0.45 5,504 112 5,616 November 14, 2017 July 1 - September 30, 2017 0.45 5,505 112 5,617 2016 February 12, 2016 October 1 - December 31, 2015 $ 0.45 $ 5,503 $ 113 $ 5,616 May 13, 2016 January 1 - March 31, 2016 0.45 5,503 113 5,616 August 12, 2016 April 1 - June 30, 2016 0.45 5,505 112 5,617 November 14, 2016 July 1 - September 30, 2016 0.45 5,503 113 5,616 Preferred Unit Distributions The following table shows the distributions declared and paid to Preferred Unitholders during the years ended December 31, 2018 and 2017 : Date Paid Period Covered by Distribution Distribution per Preferred Unit Total Distribution Declared (in thousands) 2018 February 7, 2018 October 1 - December 31, 2017 $ 30.00 $ 7,765 May 14, 2018 January 1 - March 31, 2018 30.00 7,500 August 14, 2018 April 1 - June 30, 2018 30.00 7,500 November 14, 2018 July 1 - September 30, 2018 30.00 7,500 2017 May 30, 2017 March 2 - March 31, 2017 $ 5.00 $ 2,500 August 29, 2017 April 1 - June 30, 2017 15.00 7,538 November 29, 2017 July 1 - September 30, 2017 15.00 7,650

Net Income Per Common Unit (Tab

Net Income Per Common Unit (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Reconciliation of Net Income to Weighted Average Units Outstanding	he following table reconciles the numerators and denominators of the basic and diluted net income per common unit computations and calculates basic and diluted net income per common unit: Year Ended December 31, (In thousands, except per unit data) 2018 2017 2016 Allocation of net income: Net income from continuing operations $ 122,360 $ 82,485 $ 90,626 Less: net income attributable to non-controlling interest (510 ) — — Less: income attributable to preferred unitholders (30,000 ) (25,453 ) — Net income from continuing operations attributable to common unitholders and general partner $ 91,850 $ 57,032 $ 90,626 Less: net income from continuing operations attributable to the general partner (1,837 ) (1,141 ) (1,537 ) Net income from continuing operations attributable to common unitholders $ 90,013 $ 55,891 $ 89,089 Net income from discontinued operations $ 17,687 $ 6,182 $ 6,266 Less: net income from discontinued operations attributable to the general partner (354 ) (123 ) (126 ) Net income from discontinued operations attributable to common unitholders $ 17,333 $ 6,059 $ 6,140 Net income $ 140,047 $ 88,667 $ 96,892 Less: net income attributable to non-controlling interest (510 ) — — Less: income attributable to preferred unitholders (30,000 ) (25,453 ) — Net income attributable to common unitholders and general partner $ 109,537 $ 63,214 $ 96,892 Less: net income attributable to the general partner (2,191 ) (1,264 ) (1,663 ) Net income attributable to common unitholders $ 107,346 $ 61,950 $ 95,229 Basic income per common unit: Weighted average common units—basic 12,244 12,232 12,232 Basic net income from continuing operations per common unit $ 7.35 $ 4.57 $ 7.28 Basic net income from discontinued operations per common unit $ 1.42 $ 0.50 $ 0.50 Basic net income per common unit $ 8.77 $ 5.06 $ 7.78 Year Ended December 31, (In thousands, except per unit data) 2018 2017 2016 Diluted income per common unit: Weighted average common units—basic 12,244 12,232 12,232 Plus: dilutive effect of Warrants 511 300 — Plus: dilutive effect of Preferred Units 7,479 9,418 — Weighted average common units—diluted 20,234 21,950 12,232 Net income from continuing operations $ 122,360 $ 82,485 $ 90,626 Less: net income attributable to non-controlling interest (510 ) — — Diluted net income from continuing operations attributable to common unitholders and general partner $ 121,850 $ 82,485 $ 90,626 Less: net income from continuing operations attributable to the general partner (2,437 ) (1,650 ) (1,537 ) Diluted net income from continuing operations attributable to common unitholders $ 119,413 $ 80,835 $ 89,089 Diluted net income from discontinued operations attributable to common unitholders $ 17,333 $ 6,059 $ 6,140 Net income $ 140,047 $ 88,667 $ 96,892 Less: net income attributable to non-controlling interest (510 ) — — Diluted net income attributable to common unitholders and general partner $ 139,537 $ 88,667 $ 96,892 Less: diluted net income attributable to the general partner (2,791 ) (1,773 ) (1,663 ) Diluted net income attributable to common unitholders $ 136,746 $ 86,894 $ 95,229 Diluted net income from continuing operations per common unit $ 5.90 $ 3.68 $ 7.28 Diluted net income from discontinued operations per common unit $ 0.86 $ 0.28 $ 0.50 Diluted net income per common unit $ 6.76 $ 3.96 $ 7.78

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table summarizes certain financial information for each of the Partnership's business segments: Operating Segments (In thousands) Coal Royalty and Other Soda Ash Corporate and Financing Total For the Year Ended December 31, 2018 Revenues (including affiliates) $ 202,765 $ 48,306 $ — $ 251,071 Gain on litigation settlement 25,000 — — 25,000 Gain on asset sales, net 2,441 — — 2,441 Operating and maintenance expenses (including affiliates) 29,509 — — 29,509 Depreciation, depletion and amortization 21,689 — — 21,689 General and administrative (including affiliates) — — 16,496 16,496 Asset impairments 18,280 — — 18,280 Other expense, net — — 70,178 70,178 Net income (loss) from continuing operations 160,728 48,306 (86,674 ) 122,360 Net income from discontinued operations — — — 17,687 As of December 31, 2018 Total assets of continuing operations $ 986,680 $ 247,051 $ 106,923 $ 1,340,654 Total assets of discontinued operations — — — 993 For the Year Ended December 31, 2017 Revenues (including affiliates) $ 202,323 $ 40,457 $ — $ 242,780 Gain on asset sales, net 3,545 — — 3,545 Operating and maintenance expenses 24,883 — — 24,883 Depreciation, depletion and amortization 23,414 — — 23,414 General and administrative (including affiliates) — — 18,502 18,502 Asset impairments 2,967 — — 2,967 Other expense, net — — 94,074 94,074 Net income (loss) from continuing operations 154,604 40,457 (112,576 ) 82,485 Net income from discontinued operations — — — 6,182 As of December 31, 2017 Total assets of continuing operations $ 945,237 $ 245,433 $ 6,129 $ 1,196,799 Total assets of discontinued operations — — — 192,365 For the Year Ended December 31, 2016 Revenues (including affiliates) $ 210,115 $ 40,061 $ — $ 250,176 Gain on asset sales, net 29,068 — — 29,068 Operating and maintenance expenses (including affiliates) 29,890 — — 29,890 Depreciation, depletion and amortization (including affiliates) 31,766 — — 31,766 General and administrative (including affiliates) — — 20,570 20,570 Asset impairments 15,861 — — 15,861 Other expense, net — — 90,531 90,531 Net income (loss) from continuing operations 161,666 40,061 (111,101 ) 90,626 Net income from discontinued operations — — — 6,266 Capital expenditures 5 — — 5

Equity Investment (Tables)

Equity Investment (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Summarized Financial Information	The Partnership accounts for its 49% investment in Ciner Wyoming using the equity method of accounting. Activity related to this investment is as follows: For the Year Ended December 31, (In thousands) 2018 2017 2016 Balance at beginning of period $ 245,433 $ 255,901 $ 261,942 Income allocation to NRP’s equity interests (1) 53,095 44,846 44,882 Amortization of basis difference (4,789 ) (4,389 ) (4,821 ) Comprehensive income (loss) from unconsolidated investment (138 ) (1,925 ) 448 Distribution (46,550 ) (49,000 ) (46,550 ) Balance at end of period $ 247,051 $ 245,433 $ 255,901 (1) Includes reclassifications of accumulated other comprehensive loss to income allocation to NRP equity interest of $0.5 million , $0.7 million and $0.9 million for the year ended December 31, 2018, 2017 and 2016 , respectively. The following table represents summarized financial information for Ciner Wyoming as derived from the respective financial statements for the years ended December 31, 2018 , 2017 , and 2016 : For the Year Ended December 31, (In thousands) 2018 2017 2016 Sales $ 486,759 $ 497,340 $ 475,187 Gross profit 104,053 114,202 114,232 Net income 108,357 91,523 91,596 The financial position of Ciner Wyoming is summarized as follows: December 31, (In thousands) 2018 2017 Current assets $ 138,080 $ 180,433 Noncurrent assets 252,743 228,002 Current liabilities 64,012 56,219 Noncurrent liabilities 109,921 148,401

Plant and Equipment, Net (Table

Plant and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Plant and Equipment	The Partnership’s plant and equipment consist of the following: December 31, (In thousands) 2018 2017 Plant and equipment at cost $ 6,865 $ 6,865 Less: accumulated depreciation (5,881 ) (5,517 ) Total plant and equipment, net $ 984 $ 1,348

Mineral Rights, Net (Tables)

Mineral Rights, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Extractive Industries [Abstract]
Mineral Rights	The Partnership’s mineral rights consist of the following: December 31, 2018 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,164,845 $ (451,210 ) $ 713,635 Aggregates properties 24,920 (11,814 ) 13,106 Oil and gas royalty properties 12,395 (7,632 ) 4,763 Other 13,158 (1,550 ) 11,608 Total mineral rights, net $ 1,215,318 $ (472,206 ) $ 743,112 December 31, 2017 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,170,104 $ (436,964 ) $ 733,140 Aggregates properties 37,942 (9,602 ) 28,340 Oil and gas royalty properties 12,395 (7,158 ) 5,237 Other 13,168 (1,466 ) 11,702 Total mineral rights, net $ 1,233,609 $ (455,190 ) $ 778,419
Schedule of Impairment Expense	During the years ended December 31, 2018 , 2017 and 2016 , the Partnership identified facts and circumstances that indicated that the carrying value of certain of its mineral rights exceed future cash flows from those assets and recorded non-cash impairment expense included in Asset impairments on the Consolidated Statements of Comprehensive Income as follows: For the Years Ended December 31, (In thousands) 2018 2017 2016 Coal properties (1) $ 5,259 $ 595 $ 12,088 Oil and gas properties — — 36 Aggregates and timber royalty properties (2) 13,021 2,372 1,677 Total $ 18,280 $ 2,967 $ 13,801 (1) The Partnership recorded $5.3 million of coal property impairments during the year ended December 31, 2018 primarily as a result of lease terminations, of which it recorded $5.0 million of impairment expense to fully impair certain coal properties during the three months ended December 31, 2018. The Partnership recorded $0.6 million of coal property impairments during the year ended December 31, 2017. The Partnership recorded $12.1 million of coal property impairments during the year ended December 31, 2016 primarily as a result of lease surrender and termination. The Partnership recorded $3.8 million of coal property impairment during the three months ended September 30, 2016 and the fair value of the impaired asset was reduced to $4.0 million at September 30, 2016. The Partnership recorded $8.2 million of impairment expense to fully impair certain coal property impairment during the three months ended December 31, 2016. (2) During the three months ended December 31, 2018, the Partnership recorded $13.0 million of impairment expense related to an aggregates property that the Partnership owns and leases to its former construction aggregates business, which mines, produces and sells the aggregates. The fair value of the impaired asset was reduced to $2.3 million at December 31, 2018. The Partnership recorded $2.4 million and $1.7 million of aggregates and timber royalty properties impairments during the year ended December 31, 2017 and 2016, respectively.

Intangible Assets, Net (Tables)

Intangible Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Schedule of Finite-Lived Intangible Assets	The Partnership's intangible assets included on its Consolidated Balance Sheets are as follows: December 31, (In thousands) 2018 2017 Intangible assets $ 81,109 $ 81,109 Less: accumulated amortization (38,596 ) (34,289 ) Total intangible assets, net $ 42,513 $ 46,820
Estimated Amortization Expense	The estimates of amortization expense for the years ended December 31, as indicated below, are based on current mining plans and are subject to revision as those plans change in future periods. (In thousands) Estimated Amortization Expense 2019 $ 3,251 2020 3,741 2021 3,660 2022 3,636 2023 3,602

Debt, Net (Tables)

Debt, Net (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	The Partnership's debt consists of the following: December 31, (In thousands) 2018 2017 NRP LP debt: 10.500% senior notes, with semi-annual interest payments in March and September, due March 2022, $241 million issued at par and $105 million issued at 98.75% $ 345,638 $ 345,638 Opco debt: Revolving credit facility — 60,000 Senior notes 4.91% with semi-annual interest payments in June and December, with annual principal payments in June, due June 2018 — 4,586 8.38% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2019 21,319 42,670 5.05% with semi-annual interest payments in January and July, with annual principal payments in July, due July 2020 15,290 22,946 5.55% with semi-annual interest payments in June and December, with annual principal payments in June, due June 2023 13,414 16,115 4.73% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2023 37,195 44,693 5.82% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 89,529 104,520 8.92% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 27,185 31,733 5.03% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 107,013 120,547 5.18% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 30,555 34,396 Total debt at face value $ 687,138 $ 827,844 Net unamortized debt discount (1,266 ) (1,661 ) Net unamortized debt issuance costs (13,114 ) (16,835 ) Total debt, net $ 672,758 $ 809,348 Less: current portion of long-term debt 115,184 79,740 Total long-term debt, net $ 557,574 $ 729,608
Principal Payments Due	The consolidated principal payments due are set forth below: NRP LP Opco (In thousands) Senior Notes (1) Senior Notes Credit Facility Total 2019 $ — $ 116,125 $ — $ 116,125 2020 — 46,436 — 46,436 2021 — 39,634 — 39,634 2022 345,638 39,634 — 385,272 2023 — 39,634 — 39,634 Thereafter — 60,037 — 60,037 $ 345,638 $ 341,500 $ — $ 687,138 (1) The 10.500% senior notes due 2022 were issued at a discount and were carried at $344.4 million and $344.0 million as of December 31, 2018 and 2017 , respectively.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Contractual Override, Note Receivable and Long-Term Debt	The following table shows the carrying amount and estimated fair value of the Partnership's debt and contracts receivable: December 31, 2018 December 31, 2017 (In thousands) Carrying Value Estimated Carrying Estimated Debt: NRP 2022 Senior Notes (1) $ 334,024 $ 356,871 $ 330,404 $ 366,376 Opco Senior Notes (2) 338,734 352,599 418,944 447,538 Opco Revolving Credit Facility (3) — — 60,000 60,000 Assets: Contracts receivable, current and long-term (4) $ 40,776 $ 34,704 $ 43,826 $ 30,517 (1) The Level 1 fair value is based upon quotations obtained for identical instruments on the closing trading prices near period end. (2) Due to no observable quoted prices on these instruments, the Level 3 fair value is estimated by management using quotations obtained for the NRP Senior Notes on the closing trading prices near period end. (3) The Level 3 fair value approximates the outstanding borrowing amount because the interest rates are variable and reflective of market rates and the terms of the credit facility allow the Partnership to repay this debt at any time without penalty. (4) The Level 3 fair value is determined based on the present value of future cash flow projections related to the underlying assets.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	December 31, (In thousands) 2018 2017 Projected remaining payments $ 66,495 $ 71,452 Unearned income 25,058 28,366 For the Years Ended December 31, (In thousands) 2018 2017 2016 Revenues: Coal royalty and other $ 30,777 $ 28,763 $ — Coal royalty and other — affiliates — 21,204 44,019 Transportation and processing services 23,818 14,510 — Transportation and processing services—affiliate — 6,012 19,336 Total $ 54,595 $ 70,489 $ 63,355 Expenses: Operating and maintenance expense $ 1,761 $ 1,066 $ — Operating and maintenance expense—affiliates — 452 1,347 Total $ 1,761 $ 1,518 $ 1,347
Summary of Reimbursements	For the Years Ended December 31, (In thousands) 2018 2017 2016 Operating and maintenance expenses—affiliates $ 6,170 $ 6,184 $ 8,119 General and administrative—affiliates 3,658 4,989 3,591

Major Customers (Tables)

Major Customers (Tables)	12 Months Ended
	Dec. 31, 2018
Risks and Uncertainties [Abstract]
Major customers	Revenues from customers that exceeded 10 percent of total revenues for any of the periods presented below are as follows: For the Years Ended December 31, 2018 2017 2016 (In thousands) Revenues Percent Revenues Percent Revenues Percent Foresight Energy $ 54,595 21.7 % $ 70,489 29.0 % $ 63,355 25.3 % Revenues from Foresight Energy are included within the Partnership's Coal Royalty and Other segment.

Unit-Based Compensation (Tables

Unit-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Activity in Outstanding Grants	A summary of activity in the outstanding grants during 2018 is as follows: (In thousands) Common Units Weighted Average Exercise Price Outstanding grants at January 1, 2018 — — Granted 75 29.16 Fully vested and issued (17 ) 31.24 Forfeitures (2 ) 38.28 Outstanding at December 31, 2018 56 29.10

Supplemental Quarterly Inform_2

Supplemental Quarterly Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information	The following table summarizes quarterly financial data for 2018: (In thousands, except per unit data) First (1) (2) Second (1) (2) Third (1) Fourth (3) (4) (5) Total Revenues (including affiliates) $ 59,478 $ 69,451 $ 58,207 $ 63,935 $ 251,071 Gain on litigation settlement — — — 25,000 25,000 Gain on asset sales, net 651 168 — 1,622 2,441 Asset impairments 242 — — 18,038 18,280 Income from operations 44,236 52,863 43,346 52,093 192,538 Net income from continuing operations 26,286 35,129 25,853 35,092 122,360 Income (loss) from discontinued operations (1,948 ) 2,981 2,688 13,966 17,687 Net income 24,338 38,110 28,541 49,058 140,047 Net income attributable to NRP 24,338 37,241 28,900 49,058 139,537 Net income attributable to common unitholders and general partner 16,838 29,741 21,400 41,558 109,537 Income from continuing operations per common unit Basic $ 1.50 $ 2.14 $ 1.50 $ 2.21 $ 7.35 Diluted 1.16 1.57 1.18 1.69 5.90 Net income per common unit Basic $ 1.35 $ 2.38 $ 1.71 $ 3.33 $ 8.77 Diluted 1.08 1.71 1.30 2.36 6.76 Weighted average number of common units outstanding (basic) 12,238 12,246 12,246 12,247 12,244 Weighted average number of common units outstanding (diluted) 22,125 21,383 21,840 20,394 20,234 (1) As a result of the sale of its construction aggregates business, the Partnership classified the operating results related to this business as discontinued operations in the Consolidated Statements of Comprehensive Income subsequent to the filing of the Third Quarter 2018 Form 10-Q. See below for a reconciliation to the amounts reported in the Third Quarter 2018 Form 10-Q. (2) During the third quarter of 2018 the Partnership identified an error related to its modified retrospective adoption of ASC 606 on January 1, 2018 for certain coal and aggregates royalty leases and revised its financial statements for the first and second quarter of 2018 in its Third Quarter 2018 Form 10-Q. (3) During the fourth quarter of 2018 the Partnership recorded $25 million in other income related to the Hillsboro litigation settlement. See Note 17. Commitments and Contingencies for more information. (4) During the fourth quarter of 2018 the Partnership sold its construction aggregates business for $205 million , before customary purchase price adjustments and transaction expenses, and recorded a gain of $13.1 million included in Income from discontinued operations on the Partnership's Consolidated Statement of Comprehensive Income. See Note 4. Discontinued Operations for more information. (5) During the fourth quarter of 2018 the Partnership recorded $18.0 million in aggregates and coal property impairment. See Note 11. Mineral Rights, Net for more information. The following tables reconcile the previously reported quarterly information to the quarterly financial data disclosed above: (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised First Quarter 2018 Revenues (including affiliates) $ 86,630 $ (27,152 ) $ 59,478 Gain on asset sales, net 660 (9 ) 651 Asset impairments 242 — 242 Income from operations 42,322 1,914 44,236 Net income from continuing operations 24,352 1,934 26,286 Net loss from discontinued operations (14 ) (1,934 ) (1,948 ) Net income 24,338 — 24,338 Net income attributable to NRP 24,338 — 24,338 Net income attributable to common unitholders and general partner 16,838 — 16,838 Income from continuing operations per common unit Basic $ 1.35 $ 0.15 $ 1.50 Diluted 1.08 0.09 1.16 Net income per common unit Basic $ 1.35 $ — $ 1.35 Diluted 1.08 — 1.08 Weighted average number of common units outstanding (basic) 12,238 — 12,238 Weighted average number of common units outstanding (diluted) 22,125 — 22,125 Second Quarter 2018 Revenues (including affiliates) $ 109,860 $ (40,409 ) $ 69,451 Gain on asset sales, net 210 (42 ) 168 Income from operations 55,878 (3,015 ) 52,863 Net income from continuing operations 38,144 (3,015 ) 35,129 Net income (loss) from discontinued operations (34 ) 3,015 2,981 Net income 38,110 — 38,110 Net income attributable to NRP 37,241 — 37,241 Net income attributable to common unitholders and general partner 29,741 — 29,741 Income from continuing operations per common unit Basic $ 2.38 $ (0.24 ) $ 2.14 Diluted 1.71 (0.14 ) 1.57 Net income per common unit Basic $ 2.38 $ — $ 2.38 Diluted 1.71 — 1.71 Weighted average number of common units outstanding (basic) 12,246 — 12,246 Weighted average number of common units outstanding (diluted) 21,383 — 21,383 (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised Third Quarter 2018 Revenues (including affiliates) $ 94,855 $ (36,648 ) $ 58,207 Gain on asset sales, net 163 (163 ) — Income from operations 46,066 (2,720 ) 43,346 Net income from continuing operations 28,565 (2,712 ) 25,853 Net income (loss) from discontinued operations (24 ) 2,712 2,688 Net income 28,541 — 28,541 Net income attributable to NRP 28,900 — 28,900 Net income attributable to common unitholders and general partner 21,400 — 21,400 Income from continuing operations per common unit Basic $ 1.71 $ (0.22 ) $ 1.50 Diluted 1.30 (0.12 ) 1.18 Net income per common unit Basic $ 1.71 $ — $ 1.71 Diluted 1.30 — 1.30 Weighted average number of common units outstanding (basic) 12,246 — 12,246 Weighted average number of common units outstanding (diluted) 21,840 — 21,840 The following table summarizes quarterly financial data for 2017: (In thousands, except per unit data) First (1) (2) Second (1) (3) Third (1) Fourth (1) Total (1) Revenues (including affiliates) $ 61,432 $ 58,015 $ 58,406 $ 64,927 $ 242,780 Gain on asset sales, net 29 3,184 154 178 3,545 Asset impairments 1,778 — — 1,189 2,967 Income from operations 38,124 47,522 43,052 47,861 176,559 Debt modification expense 7,807 132 — — 7,939 Loss on extinguishment of debt — 4,107 — — 4,107 Net income from continuing operations 7,588 23,153 23,079 28,665 82,485 Net income (loss) from discontinued operations (1,684 ) 2,837 2,987 2,042 6,182 Net income 5,904 25,990 26,066 30,707 88,667 Net income attributable to common unitholders and general partner 3,404 18,452 18,416 22,942 63,214 Income from continuing operations per common unit Basic $ 0.41 $ 1.25 $ 1.24 $ 1.67 $ 4.57 Diluted 0.50 1.01 0.94 1.18 3.68 Net income per common unit Basic $ 0.28 $ 1.47 $ 1.48 $ 1.84 $ 5.06 Diluted 0.28 1.13 1.07 1.26 3.96 Weighted average number of common units outstanding (basic) 12,232 12,232 12,232 12,232 12,232 Weighted average number of common units outstanding (diluted) 14,945 22,459 23,980 23,874 21,950 (1) As a result of the sale of its construction aggregates business, the Partnership classified the operating results related to this business as discontinued operations in the Consolidated Statements of Comprehensive Income subsequent to the filing of the 2017 Form 10-K. See below for a reconciliation to the amounts reported in the 2017 Form 10-K. (2) During the first quarter of 2017 the Partnership incurred $7.8 million of debt modification costs as a result of the exchange of $241 million of our 2018 Senior Notes for 2022 Senior Notes. (3) During the second quarter of 2017 the Partnership incurred a $4.1 million loss on extinguishment of debt related to the 4.563% premium paid to redeem the 2018 Senior Notes in April 2017. The following tables reconcile the previously reported quarterly information to the quarterly financial data disclosed above: (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised First Quarter 2017 Revenues (including affiliates) $ 88,653 $ (27,221 ) $ 61,432 Gain on asset sales, net 44 (15 ) 29 Asset impairments 1,778 — 1,778 Income from operations 37,042 1,082 38,124 Debt modification expense 7,807 — 7,807 Net income from continuing operations 6,111 1,477 7,588 Net income (loss) from discontinued operations (207 ) (1,477 ) (1,684 ) Net income 5,904 — 5,904 Net income attributable to common unitholders and general partner 3,404 — 3,404 Income from continuing operations per common unit Basic $ 0.30 $ 0.12 $ 0.41 Diluted 0.30 0.10 0.50 Net income per common unit Basic $ 0.28 $ — $ 0.28 Diluted 0.28 — 0.28 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 14,945 — 14,945 Second Quarter 2017 Revenues (including affiliates) $ 91,570 $ (33,555 ) $ 58,015 Gain on asset sales, net 3,361 (177 ) 3,184 Income from operations 50,404 (2,882 ) 47,522 Debt modification expense 132 — 132 Loss on extinguishment of debt 4,107 — 4,107 Net income from continuing operations 25,857 (2,704 ) 23,153 Net income (loss) from discontinued operations 133 2,704 2,837 Net income 25,990 — 25,990 Net income attributable to common unitholders and general partner 18,452 — 18,452 Income from continuing operations per common unit Basic $ 1.46 $ (0.22 ) $ 1.25 Diluted 1.13 (0.12 ) 1.01 Net income per common unit Basic $ 1.47 $ — $ 1.47 Diluted 1.13 — 1.13 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 22,459 — 22,459 (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised Third Quarter 2017 Revenues (including affiliates) $ 93,116 $ (34,710 ) $ 58,406 Gain on asset sales, net 171 (17 ) 154 Income from operations 46,531 (3,479 ) 43,052 Net income from continuing operations 26,499 (3,420 ) 23,079 Net income (loss) from discontinued operations (433 ) 3,420 2,987 Net income 26,066 — 26,066 Net income attributable to common unitholders and general partner 18,416 — 18,416 Income from continuing operations per common unit Basic $ 1.51 $ (0.27 ) $ 1.24 Diluted 1.08 (0.14 ) 0.94 Net income per common unit Basic $ 1.48 $ — $ 1.48 Diluted 1.07 — 1.07 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 23,980 — 23,980 Fourth Quarter 2017 Revenues (including affiliates) $ 100,822 $ (35,895 ) $ 64,927 Gain on asset sales, net 280 (102 ) 178 Asset impairments 1,253 (64 ) 1,189 Income from operations 49,998 (2,137 ) 47,861 Net income from continuing operations 30,741 (2,076 ) 28,665 Net income (loss) from discontinued operations (34 ) 2,076 2,042 Net income 30,707 — 30,707 Net income attributable to common unitholders and general partner 22,942 — 22,942 Income from continuing operations per common unit Basic $ 1.84 $ (0.17 ) $ 1.67 Diluted 1.26 (0.09 ) 1.18 Net income per common unit Basic $ 1.84 $ — $ 1.84 Diluted 1.26 — 1.26 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 23,874 — 23,874 (In thousands, except per unit data) As Originally Reported Reclassified to Discontinued Operations Revised Total 2017 Revenues (including affiliates) $ 374,161 $ (131,381 ) $ 242,780 Gain on asset sales, net 3,856 (311 ) 3,545 Asset impairments 3,031 (64 ) 2,967 Income from operations 183,975 (7,416 ) 176,559 Debt modification expense 7,939 — 7,939 Loss on extinguishment of debt 4,107 — 4,107 Net income from continuing operations 89,208 (6,723 ) 82,485 Net income (loss) from discontinued operations (541 ) 6,723 6,182 Net income 88,667 — 88,667 Net income attributable to common unitholders and general partner 63,214 — 63,214 Income from continuing operations per common unit — Basic $ 5.11 $ (0.54 ) $ 4.57 Diluted 3.98 (0.30 ) 3.68 Net income per common unit Basic $ 5.06 $ — $ 5.06 Diluted 3.96 — 3.96 Weighted average number of common units outstanding (basic) 12,232 — 12,232 Weighted average number of common units outstanding (diluted) 21,950 — 21,950

Organization and Nature of Op_2

Organization and Nature of Operations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018companysegment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments | segment	2
Number of operating companies owned | company	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Plant and Equipment Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2018
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives	Life of Lease
Minimum | Buildings and Improvements
Property, Plant and Equipment [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives	20 years
Minimum | Machinery and Equipment
Property, Plant and Equipment [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives	5 years
Maximum | Buildings and Improvements
Property, Plant and Equipment [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives	40 years
Maximum | Machinery and Equipment
Property, Plant and Equipment [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives	12 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Jul. 31, 2013	Jan. 31, 2013
Schedule Of Significant Accounting Policies [Line Items]
Allowance for doubtful accounts					$ 4,800					$ 4,800
Allowance for doubtful accounts - other current assets	$ (1,200)				(1,200)				$ (1,200)	(1,200)
Bad debt expense									(100)	(2,400)	$ (300)
Balance Sheet Impact of Adoption of New Revenue Standard
Accounts Receivable Net, Including Related Party Receivables	32,058								32,058			$ 29,086
Assets	1,341,647				1,389,164				1,341,647	1,389,164
Current portion of deferred revenue	3,509				0				3,509	0
Deferred revenue	49,044				100,605				49,044	100,605
Liabilities	756,514				953,916				756,514	953,916
Common unitholders’ interest	355,113				199,851				355,113	199,851		268,908
General partner's interest	5,014				1,857				5,014	1,857		3,266
Partners' Capital	423,481				265,211				423,481	265,211		335,677
Liabilities and Equity	1,341,647				1,389,164				1,341,647	1,389,164
Income Statement Impact of Adoption of New Revenue Standard
Net income from continuing operations	35,092	$ 25,853	$ 35,129	$ 26,286	28,665	$ 23,079	$ 23,153	$ 7,588	122,360	82,485	90,626
Net income	$ 49,058	$ 28,541	$ 38,110	$ 24,338	$ 30,707	$ 26,066	$ 25,990	$ 5,904	$ 140,047	$ 88,667	$ 96,892
Basic net income per common unit	$ 3.33	$ 1.71	$ 2.38	$ 1.35	$ 1.84	$ 1.48	$ 1.47	$ 0.28	$ 8.77	$ 5.06	$ 7.78
Diluted net income per common unit	$ 2.36	$ 1.30	$ 1.71	$ 1.08	$ 1.26	$ 1.07	$ 1.13	$ 0.28	$ 6.76	$ 3.96	$ 7.78
Ciner Wyoming
Schedule Of Significant Accounting Policies [Line Items]
Percentage of partnership interest owned (percent)	49.00%								49.00%				49.00%	48.51%
Leasehold Improvements
Schedule Of Significant Accounting Policies [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives									Life of Lease
Minimum
Schedule Of Significant Accounting Policies [Line Items]
Lessor, Operating Lease, Term of Contract	5 years								5 years
Operating Lease, Late Payment Recovery Period									3 years
Minimum | Buildings and Improvements
Schedule Of Significant Accounting Policies [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives									20 years
Minimum | Machinery and Equipment
Schedule Of Significant Accounting Policies [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives									5 years
Maximum
Schedule Of Significant Accounting Policies [Line Items]
Lessor, Operating Lease, Term of Contract	40 years								40 years
Operating Lease, Late Payment Recovery Period									5 years
Maximum | Buildings and Improvements
Schedule Of Significant Accounting Policies [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives									40 years
Maximum | Machinery and Equipment
Schedule Of Significant Accounting Policies [Line Items]
Period of assets which are depreciated on straight line basis over their useful lives									12 years
Coal Royalty and Other
Income Statement Impact of Adoption of New Revenue Standard
Revenues and Revenue from Related Parties									$ 178,878
Coal Royalty
Balance Sheet Impact of Adoption of New Revenue Standard
Accounts Receivable Net, Including Related Party Receivables	$ 29,001								29,001			25,443
Current portion of deferred revenue	3,509								3,509			1,022
Deferred revenue	49,044								49,044			33,992
Calculated under Revenue Guidance in Effect before Topic 606
Balance Sheet Impact of Adoption of New Revenue Standard
Accounts Receivable Net, Including Related Party Receivables	27,520				$ 24,211				27,520	$ 24,211
Assets	1,337,109								1,337,109
Current portion of deferred revenue	0				0				0	0
Deferred revenue	62,783				100,605				62,783	100,605
Liabilities	766,744								766,744
Common unitholders’ interest	340,640				199,851				340,640	199,851
General partner's interest	4,719				1,857				4,719	1,857
Partners' Capital	408,713				$ 265,211				408,713	$ 265,211
Liabilities and Equity	1,337,109								1,337,109
Income Statement Impact of Adoption of New Revenue Standard
Revenues and Revenue from Related Parties									234,428
Net income from continuing operations									178,058
Net income									$ 195,745
Basic net income per common unit									$ 13.23
Diluted net income per common unit									$ 9.46
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Balance Sheet Impact of Adoption of New Revenue Standard
Accounts Receivable Net, Including Related Party Receivables	4,538								$ 4,538			4,875
Assets	4,538								4,538
Current portion of deferred revenue	3,509								3,509			1,022
Deferred revenue	(13,739)								(13,739)			(66,613)
Liabilities	(10,230)								(10,230)
Common unitholders’ interest	14,473								14,473			69,057
General partner's interest	295								295			1,409
Partners' Capital	14,768								14,768			$ 70,466
Liabilities and Equity	4,538								4,538
Income Statement Impact of Adoption of New Revenue Standard
Revenues and Revenue from Related Parties									(55,550)
Net income from continuing operations									(55,698)
Net income									$ (55,698)
Basic net income per common unit									$ (4.46)
Diluted net income per common unit									$ (2.70)
Lease Modifications of Existing Coal Royalty Leases [Member]
Income Statement Impact of Adoption of New Revenue Standard
Deferred Revenue, Additions	$ 7,200
Settled Litigation [Member] | Lawsuit Against Hillsboro Energy LLC
Income Statement Impact of Adoption of New Revenue Standard
Loss Contingency, Forfeiture of Recoupable Lease Balance in Settlement									$ 37,400
Settled Litigation [Member] | Lawsuit Against Hillsboro Energy LLC | Difference between Revenue Guidance in Effect before and after Topic 606
Income Statement Impact of Adoption of New Revenue Standard
Loss Contingency, Forfeiture of Recoupable Lease Balance in Settlement									$ 33,400

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Narrative (Details) - Royalty Leases $ in Millions	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments, Due in Five Years	$ 1.8
Operating Leases, Future Minimum Payments, Due Thereafter	$ 1

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 202,765
Revenues	$ 63,935	$ 58,207	$ 69,451	$ 59,478	$ 64,927	$ 58,406	$ 58,015	$ 61,432	251,071	$ 242,780	$ 250,176
Coal Royalty and Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									178,878
Revenues									178,394	$ 158,399	$ 144,520
Coal Royalty and Other | Coal Royalty Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									129,341
Coal Royalty and Other | Production Lease Minimum Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									8,207
Coal Royalty and Other | Minimum Lease Straight-Line Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									2,362
Coal Royalty and Other | Wheelage Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									6,484
Coal Royalty and Other | Coal Overriding Royalty Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									13,878
Coal Royalty and Other | Aggregates Royalty Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									4,739
Coal Royalty and Other | Oil and Gas Royalty Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									6,608
Coal Royalty and Other | Property Tax Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									5,422
Coal Royalty and Other | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									1,837
Coal Royalty and Other | Transportation and processing services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									13,200
Revenues									23,887
Coal Royalty and Other | Transportation and Processing
Disaggregation of Revenue [Line Items]
Sales-type Lease, Revenue									$ 10,700

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Accounts Receivable Net, Including Related Party Receivables	$ 32,058	$ 29,086
Current portion of deferred revenue	3,509		$ 0
Deferred revenue	49,044		$ 100,605
Coal Royalty
Revenue from External Customer [Line Items]
Accounts Receivable Net, Including Related Party Receivables	29,001	25,443
Prepaid Expense and Other Assets	2,483	2,830
Current portion of deferred revenue	3,509	1,022
Deferred revenue	49,044	33,992
Accounting Standards Update 2014-09
Revenue from External Customer [Line Items]
Accrued Fees and Other Revenue Receivable	1,900	$ 1,900
Accounting Standards Update 2014-09 | Coal Royalty
Revenue from External Customer [Line Items]
Accrued Fees and Other Revenue Receivable	$ 4,430

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Revenue Recognition Deferred Revenue Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Production Leases, Recoupment Recognized		$ 10,178
Deferred Revenue	$ 52,553	52,553	$ 35,014	$ 100,605
Deferred Revenue, Revenue Recognized		20,242
Deferred Revenue, Contractual Minimum Payments		5,592
Increase (Decrease) in Deferred Revenue and Customer Advances and Deposits		32,189
Royalty Revenue Recognized		7,169
Production Leases, Minimum Lease Revenue		935
Deferred Revenue, Leases, Amortization		1,960
Contract with Customer, Liability, Revenue Recognized		20,242
Accounting Standards Update 2014-09
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Deferred revenue recognized in Partners' Capital	67,500	67,500
Deferred Revenue			(65,591)
Accrued Fees and Other Revenue Receivable	1,900	$ 1,900	$ 1,900
Lease Modifications of Existing Coal Royalty Leases [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Deferred Revenue, Additions	$ 7,200
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	6 years	6 years

Revenue from Contracts with C_7

Revenue from Contracts with Customers - Revenue Remaining Performance Obligation (Details) $ in Thousands	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 13,072
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	7 months 6 days
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 13,060
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year 3 months 18 days
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 41,202
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 years

Discontinued Operations - Narra

Discontinued Operations - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	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	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on asset sales, net		$ 1,622	$ 0	$ 168	$ 651	$ 178	$ 154	$ 3,184	$ 29	$ 2,441	$ 3,545	$ 29,068
Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Capital Expenditure, Discontinued Operations										10,900	7,600	6,700
Disposal Group, Including Discontinued Operation, Consideration		205,000								205,000			$ 116,100
Gain on asset sales, net		13,100								$ 13,100
Floating Rate Revolving Credit Facility Due April Two Thousand Twenty [Member] | Opco
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt Instrument, Asset Sales Proceeds, Required to Repay Outstanding Debt, Percent										75.00%
Senior Notes | Opco
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt Instrument, Asset Sales Proceeds, Required to Repay Outstanding Debt, Percent										25.00%
Repayments of Debt										$ 80,700	$ 80,800	$ 82,900
Restricted Cash		$ 55,000								$ 55,000
Subsequent Event | Senior Notes | Opco
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of Debt	$ 49,000

Discontinued Operations - Summa

Discontinued Operations - Summary of Financial Results of Discontinued Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 0	$ 2,847	$ 1,200	$ 11,529
Accounts receivable, net	993	23,967
Inventory		7,553
Prepaid expenses and other		2,056
Total current assets of discontinued operations	993	36,423
Noncurrent assets
Land		1,239
Plant and equipment, net		44,822
Mineral rights, net		105,466
Intangible assets, net		2,734
Other assets		1,681
Total assets of discontinued operations	993	192,365
Current liabilities:
Accounts payable (including affiliates)	181	6,019
Accrued liabilities	766	5,348
Other		401
Total current liabilities of discontinued operations	947	11,768
Noncurrent liabilities
Other non-current liabilities		2,220
Total liabilities of discontinued operations	947	13,988
Discontinued Operations, Held-for-sale [Member]
Revenues and other income:
Construction aggregates	116,066	112,970	103,755
Road construction and asphalt paving services	18,400	18,411	17,047
Oil and gas	(3)	38	16,486
Gain on asset sales, net	13,414	22	8,287
Total revenues and other income	147,877	131,441	145,575
Operating expenses
Operating and maintenance expenses (including affiliates)	117,702	111,923	112,159
Depreciation, depletion and amortization	12,218	12,579	22,033
Asset impairments	232	64	1,629
Total operating expenses	130,152	124,566	135,821
Interest expense, net	38	693	3,488
Income (loss) from discontinued operations	17,687	6,182	6,266
Disposal Group, Including Discontinued Operation, Additional Disclosures [Abstract]
Cash paid for interest	0	0	1,906
Plant, equipment and mineral rights funded with accounts payable or accrued liabilities	881	294	0
NRP Oil and Gas [Domain]
Current assets:
Cash and cash equivalents		0
Accounts receivable, net	988	991
Inventory		0
Prepaid expenses and other		0
Total current assets of discontinued operations		991
Noncurrent assets
Land		0
Plant and equipment, net		0
Mineral rights, net		0
Intangible assets, net		0
Other assets		0
Total assets of discontinued operations	988	991
Current liabilities:
Accounts payable (including affiliates)	0	0
Accrued liabilities	0	0
Other		401
Total current liabilities of discontinued operations		401
Noncurrent liabilities
Other non-current liabilities		0
Total liabilities of discontinued operations	0	401
Construction Aggregates
Current assets:
Cash and cash equivalents		2,847
Accounts receivable, net	5	22,976
Inventory		7,553
Prepaid expenses and other		2,056
Total current assets of discontinued operations		35,432
Noncurrent assets
Land		1,239
Plant and equipment, net		44,822
Mineral rights, net		105,466
Intangible assets, net		2,734
Other assets		1,681
Total assets of discontinued operations	5	191,374
Current liabilities:
Accounts payable (including affiliates)	181	6,019
Accrued liabilities	766	5,348
Other		0
Total current liabilities of discontinued operations		11,367
Noncurrent liabilities
Other non-current liabilities		2,220
Total liabilities of discontinued operations	947	13,587
NRP Oil and Gas [Domain] | Discontinued Operations, Held-for-sale [Member]
Revenues and other income:
Construction aggregates	0	0	0
Road construction and asphalt paving services	0	0	0
Oil and gas	(3)	38	16,486
Gain on asset sales, net	0	(289)	8,274
Total revenues and other income	(3)	(251)	24,760
Operating expenses
Operating and maintenance expenses (including affiliates)	134	290	11,503
Depreciation, depletion and amortization	0	0	7,527
Asset impairments	0	0	564
Total operating expenses	134	290	19,594
Interest expense, net		0	3,488
Income (loss) from discontinued operations	(137)	(541)	1,678
Construction Aggregates | Discontinued Operations, Held-for-sale [Member]
Revenues and other income:
Construction aggregates	116,066	112,970	103,755
Road construction and asphalt paving services	18,400	18,411	17,047
Oil and gas	0	0	0
Gain on asset sales, net	13,414	311	13
Total revenues and other income	147,880	131,692	120,815
Operating expenses
Operating and maintenance expenses (including affiliates)	117,568	111,633	100,656
Depreciation, depletion and amortization	12,218	12,579	14,506
Asset impairments	232	64	1,065
Total operating expenses	130,018	124,276	116,227
Interest expense, net	38	693	0
Income (loss) from discontinued operations	$ 17,824	$ 6,723	$ 4,588

Class A Convertible Preferred_3

Class A Convertible Preferred Units and Warrants - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred units issued (in shares)		250,000	258,844
Preferred unit purchase price		$ 1,000	$ 1,000
Class A Convertible Preferred Units
Class of Stock [Line Items]
Dividends, Preferred Stock, Paid-in-Kind, Cash Redemption Payment		$ 8,844	$ 0	$ 0
Preferred units issued (in shares)	250,000
Preferred unit purchase price	$ 1,000
Preferred Units, Origination Fee, Percent	2.50%
Dividend rate (as a percent)	12.00%
Convertible Preferred Units, Redemption Price, Minimum	$ 51
Convertible Preferred Units, Maximum Redeemed Units, Percent	33.00%
Debt Instrument, Covenants, Consolidated Leverage Ratio, Minimum	3.25
Debt Instrument, Covenants, Distributable Cash Flow Ratio, Maximum	1.2
Distribution amount (in dollars per share)	$ 0.45
Purchaser approval rights threshold (as a percent)	20.00%
Warrants at $22.81 Strike | Warrant Holders
Class of Stock [Line Items]
Class of Warrant or Right, Warrants Issued	1,750,000
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 22.81
Warrants at $34.00 Strike | Warrant Holders
Class of Stock [Line Items]
Class of Warrant or Right, Warrants Issued	2,250,000	2,250,000
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 34	$ 34
Debt Instrument, Redemption, Period One | Class A Convertible Preferred Units
Class of Stock [Line Items]
Convertible Preferred Units, Conversion to Common Units, Discount Percentage	7.50%
Convertible Preferred Units, Purchase Price Multiplier	1.50
Debt Instrument, Redemption, Period Two | Class A Convertible Preferred Units
Class of Stock [Line Items]
Convertible Preferred Units, Purchase Price Multiplier	1.70
Debt Instrument, Redemption, Period Three | Class A Convertible Preferred Units
Class of Stock [Line Items]
Convertible Preferred Units, Conversion to Common Units, Discount Percentage	10.00%
Convertible Preferred Units, Purchase Price Multiplier	1.85
Preferred Stock
Class of Stock [Line Items]
Transaction price, gross	$ 250,000
Preferred Partner | Preferred Stock
Class of Stock [Line Items]
Temporary Equity, Stock Issued During Period, Shares, New Issues	250,000

Class A Convertible Preferred_4

Class A Convertible Preferred Units and Warrants - Preferred Units and Warrants Issued (Details) - USD ($) $ in Thousands	Mar. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Distribution paid-in-kind (in shares)			8,844
Warrant holders interest	$ 66,816	$ 66,816	$ 66,816
Dividends, Preferred Stock, Paid-in-kind			8,844
Class A Convertible Preferred Units (250,000 and 258,844 units issued and outstanding at December 31, 2018 and 2017, respectively, at $1,000 par value per unit; liquidation preference of $1,500 per unit)		$ 164,587	$ 173,431
Distribution Made to Limited Partner, Unit Redemption		(8,844)
Preferred Stock
Class of Stock [Line Items]
Transaction price, gross	250,000
Structuring, origination and other fees to Preferred Purchasers	(7,900)
Payments of Stock Issuance Costs	10,697
Transaction price, net	231,403
Preferred Partner | Preferred Stock
Class of Stock [Line Items]
Preferred Units, net	$ 164,587
Temporary Equity, Shares Outstanding		250,000	258,844	0
Class A Convertible Preferred Units (250,000 and 258,844 units issued and outstanding at December 31, 2018 and 2017, respectively, at $1,000 par value per unit; liquidation preference of $1,500 per unit)		$ 164,587	$ 173,431	$ 0
Temporary Equity, Stock Issued During Period, Shares, New Issues	250,000
Class A Convertible Preferred Units
Class of Stock [Line Items]
Dividends, Preferred Stock, Paid-in-Kind, Cash Redemption Payment		$ (8,844)	$ 0	$ 0

Common and Preferred Unit Dis_3

Common and Preferred Unit Distributions Narrative (Details) - USD ($) $ in Thousands	Mar. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Temporary Equity [Line Items]
Income attributable to preferred unitholders		$ 30,000	$ 25,453	$ 0
Class A Convertible Preferred Units
Temporary Equity [Line Items]
Dividend rate (as a percent)	12.00%
Dividends, Preferred Stock, Paid-in-Kind, Cash Redemption Payment		$ 8,844	$ 0	$ 0
General Partner
Temporary Equity [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		2.00%

Common and Preferred Unit Dis_4

Common and Preferred Unit Distributions Schedule of Distributions Paid (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 14, 2018	Aug. 14, 2018	May 14, 2018	Feb. 14, 2018	Feb. 07, 2018	Nov. 29, 2017	Nov. 14, 2017	Aug. 29, 2017	Aug. 14, 2017	May 30, 2017	May 12, 2017	Feb. 14, 2017	Nov. 14, 2016	Aug. 12, 2016	May 13, 2016	Feb. 12, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 14, 2019
Class of Stock [Line Items]
Distribution paid-in-kind (in shares)																		8,844
Common unitholders and general partner
Class of Stock [Line Items]
Distributions per common unit (in dollars per share)	$ 0.45	$ 0.45	$ 0.45	$ 0.45			$ 0.45		$ 0.45		$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45
Total distributions paid	$ 5,623	$ 5,623	$ 5,623	$ 5,617			$ 5,617		$ 5,616		$ 5,619	$ 5,615	$ 5,616	$ 5,617	$ 5,616	$ 5,616	$ 22,486	$ 22,467	$ 22,465
Common unitholders
Class of Stock [Line Items]
Distributions to common unitholders and general partner	5,510	5,511	5,510	5,505			5,505		5,504		5,506	5,503	5,503	5,505	5,503	5,503
General Partner
Class of Stock [Line Items]
Distributions to common unitholders and general partner																	22,486	22,467	22,465
Distributions paid to general partners	$ 113	$ 112	$ 113	$ 112			$ 112		$ 112		$ 113	$ 112	$ 113	$ 112	$ 113	$ 113
Preferred Partner
Class of Stock [Line Items]
Distributions to common unitholders and general partner																	30,265	8,844	$ 0
Total distributions paid																	$ 30,265	$ 17,688
Preferred Partner | Preferred Stock
Class of Stock [Line Items]
Distributions per common unit (in dollars per share)	$ 30	$ 30	$ 30		$ 30	$ 15		$ 15		$ 5
Total Distributions Declared	$ 7,500	$ 7,500	$ 7,500		$ 7,765	$ 7,650		$ 7,538		$ 2,500
Subsequent Event | Preferred Partner | Preferred Stock
Class of Stock [Line Items]
Total Distributions Declared																				$ 7,500

Net Income Per Common Unit (Det

Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Mar. 02, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income attributable to common unitholders and general partner		$ 41,558	$ 21,400	$ 29,741	$ 16,838	$ 22,942	$ 18,416	$ 18,452	$ 3,404	$ 109,537	$ 63,214	$ 96,892
Allocation of net income:
Net income from continuing operations		35,092	25,853	35,129	26,286	28,665	23,079	23,153	7,588	122,360	82,485	90,626
Net income attributable to non-controlling interest										(510)	0	0
Diluted Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest										121,850	82,485	90,626
Net Income (Loss) Allocated to General Partners and Limited Partners, Diluted										139,537	88,667	96,892
Less: income attributable to preferred unitholders										(30,000)	(25,453)	0
Income (Loss) from Continuing Operations and Income Attributable to Preferred Unitholders, Including Portion Attributable to Noncontrolling Interest, Allocated to General Partner and Limited Partners										91,850	57,032	90,626
Less: net income from continuing operations attributable to the general partner										(1,837)	(1,141)	(1,537)
Net income from continuing operations attributable to common unitholders										90,013	55,891	89,089
Income from discontinued operations		13,966	2,688	2,981	(1,948)	2,042	2,987	2,837	(1,684)	17,687	6,182	6,266
Less: net income from discontinued operations attributable to the general partner										(354)	(123)	(126)
Net income from discontinued operations attributable to common unitholders										17,333	6,059	6,140
Net income		49,058	28,541	38,110	24,338	$ 30,707	$ 26,066	$ 25,990	$ 5,904	140,047	88,667	96,892
Net income (loss)		$ 49,058	$ 28,900	$ 37,241	$ 24,338					139,537	88,667	96,892
Net income attributable to the general partner										(2,191)	(1,264)	(1,663)
Net income attributable to common unitholders										$ 107,346	$ 61,950	$ 95,229
Weighted average common units—basic (in shares)		12,247	12,246	12,246	12,238	12,232	12,232	12,232	12,232	12,244	12,232	12,232
Basic net income from continuing operations per common unit		$ 2.21	$ 1.50	$ 2.14	$ 1.50	$ 1.67	$ 1.24	$ 1.25	$ 0.41	$ 7.35	$ 4.57	$ 7.28
Basic net income from discontinued operations per common unit										1.42	0.50	0.50
Basic net income per common unit		$ 3.33	$ 1.71	$ 2.38	$ 1.35	$ 1.84	$ 1.48	$ 1.47	$ 0.28	$ 8.77	$ 5.06	$ 7.78
Dilutive effect of Warrants (in shares)										511	300	0
Dilutive effect of Preferred Units (in shares)										7,479	9,418	0
Weighted average common units—diluted (in shares)		20,394	21,840	21,383	22,125	23,874	23,980	22,459	14,945	20,234	21,950	12,232
Less: net income from continuing operations attributable to the general partner										$ (2,437)	$ (1,650)	$ (1,537)
Diluted net income from continuing operations attributable to common unitholders										119,413	80,835	89,089
Diluted net income from discontinued operations attributable to common unitholders										17,333	6,059	6,140
Less: diluted net income attributable to the general partner										(2,791)	(1,773)	(1,663)
Diluted net income attributable to common unitholders										$ 136,746	$ 86,894	$ 95,229
Diluted net income from continuing operations per common unit		$ 1.69	$ 1.18	$ 1.57	$ 1.16	$ 1.18	$ 0.94	$ 1.01	$ 0.50	$ 5.90	$ 3.68	$ 7.28
Diluted net income from discontinued operations per common unit										0.86	0.28	0.50
Diluted net income per common unit		2.36	$ 1.30	$ 1.71	$ 1.08	$ 1.26	$ 1.07	$ 1.13	$ 0.28	$ 6.76	$ 3.96	$ 7.78
Warrant Holders | Warrants at $22.81 Strike
Class of Warrant or Right, Warrants Issued	1,750
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 22.81
Warrant Holders | Warrants at $34.00 Strike
Class of Warrant or Right, Warrants Issued	2,250									2,250
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 34	$ 34								$ 34

Segment Information - Additiona

Segment Information - Additional Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jul. 31, 2016USD ($)	Jul. 31, 2013	Jan. 31, 2013
Segment Reporting Information [Line Items]
Number of operating segments | segment									2
Gain on asset sales, net	$ 1,622	$ 0	$ 168	$ 651	$ 178	$ 154	$ 3,184	$ 29	$ 2,441	$ 3,545	$ 29,068
Ciner Wyoming
Segment Reporting Information [Line Items]
Percentage of partnership interest owned (percent)	49.00%								49.00%				49.00%	48.51%
Discontinued Operations, Held-for-sale
Segment Reporting Information [Line Items]
Disposal Group, Including Discontinued Operation, Consideration	$ 205,000								$ 205,000			$ 116,100
Gain on asset sales, net	$ 13,100								$ 13,100

Segment Information - Schedule

Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gain on asset sales, net	$ 1,622	$ 0	$ 168	$ 651	$ 178	$ 154	$ 3,184	$ 29	$ 2,441	$ 3,545	$ 29,068
Operating and maintenance expenses (including affiliates)									29,509	24,883	29,890
General and administrative (including affiliates)									16,496	18,502	20,570
Depreciation, depletion and amortization (including affiliates)									21,689	23,414	31,766
Asset impairments	18,038	0	0	242	1,189	0	0	1,778	18,280	2,967	15,861
Other expense, net									70,178	94,074	90,531
Net income from continuing operations	35,092	25,853	35,129	26,286	28,665	23,079	23,153	7,588	122,360	82,485	90,626
Net income (loss) from discontinued operations									17,687
Income from discontinued operations	13,966	2,688	2,981	(1,948)	2,042	2,987	2,837	(1,684)	17,687	6,182	6,266
Capital expenditures											5
Total assets	1,341,647				1,389,164				1,341,647	1,389,164
Revenues	63,935	58,207	69,451	59,478	64,927	$ 58,406	$ 58,015	$ 61,432	251,071	242,780	250,176
Gain on litigation settlement	25,000	$ 0	$ 0	$ 0					25,000	0	0
Corporate and Financing
Segment Reporting Information [Line Items]
Gain on asset sales, net									0	0	0
Operating and maintenance expenses (including affiliates)									0	0	0
General and administrative (including affiliates)									16,496	18,502	20,570
Depreciation, depletion and amortization (including affiliates)									0	0	0
Asset impairments									0	0	0
Other expense, net									70,178	94,074	90,531
Net income from continuing operations									(86,674)	(112,576)	(111,101)
Net income (loss) from discontinued operations									0	0	0
Capital expenditures											0
Revenues									0	0	0
Gain on litigation settlement									0
Coal Royalty and Other
Segment Reporting Information [Line Items]
Revenues									178,394	158,399	144,520
Coal Royalty and Other | Operating Segments
Segment Reporting Information [Line Items]
Gain on asset sales, net									2,441	3,545	29,068
Operating and maintenance expenses (including affiliates)									29,509	24,883	29,890
General and administrative (including affiliates)									0	0	0
Depreciation, depletion and amortization (including affiliates)									21,689	23,414	31,766
Asset impairments									18,280	2,967	15,861
Other expense, net									0	0	0
Net income from continuing operations									160,728	154,604	161,666
Net income (loss) from discontinued operations									0	0	0
Capital expenditures											5
Revenues									202,765	202,323	210,115
Gain on litigation settlement									25,000
Soda Ash
Segment Reporting Information [Line Items]
Revenues									48,306	40,457	40,061
Soda Ash | Operating Segments
Segment Reporting Information [Line Items]
Gain on asset sales, net									0	0	0
Operating and maintenance expenses (including affiliates)									0	0	0
General and administrative (including affiliates)									0	0	0
Depreciation, depletion and amortization (including affiliates)									0	0	0
Asset impairments									0	0	0
Other expense, net									0	0	0
Net income from continuing operations									48,306	40,457	40,061
Net income (loss) from discontinued operations									0	0	0
Capital expenditures											0
Revenues									48,306	40,457	$ 40,061
Gain on litigation settlement									0
Continuing Operations
Segment Reporting Information [Line Items]
Total assets	1,340,654				1,196,799				1,340,654	1,196,799
Continuing Operations | Corporate and Financing
Segment Reporting Information [Line Items]
Total assets	106,923				6,129				106,923	6,129
Continuing Operations | Coal Royalty and Other | Operating Segments
Segment Reporting Information [Line Items]
Total assets	986,680				945,237				986,680	945,237
Continuing Operations | Soda Ash | Operating Segments
Segment Reporting Information [Line Items]
Total assets	247,051				245,433				247,051	245,433
Discontinued Operations
Segment Reporting Information [Line Items]
Total assets	993				192,365				993	192,365
Discontinued Operations | Corporate and Financing
Segment Reporting Information [Line Items]
Total assets	0				0				0	0
Discontinued Operations | Coal Royalty and Other | Operating Segments
Segment Reporting Information [Line Items]
Total assets	0				0				0	0
Discontinued Operations | Soda Ash | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 0				$ 0				$ 0	$ 0

Equity Investment - Additional

Equity Investment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2013	Jan. 31, 2013
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 247,051	$ 245,433
Comprehensive income (loss) from unconsolidated investment	$ 139,898	87,020	$ 97,378
Weighted average useful life of assets (in years)	28 years
Ciner Wyoming
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 247,051	245,433	255,901	$ 261,942
Income allocation to NRP’s equity interests	53,095	44,846	44,882
Amortization of basis difference	(4,789)	(4,389)	(4,821)
Comprehensive income (loss) from unconsolidated investment	(138)	(1,925)	448
Distribution	$ (46,550)	(49,000)	(46,550)
Ciner Wyoming
Schedule of Equity Method Investments [Line Items]
Percentage of partnership interest owned (percent)	49.00%				49.00%	48.51%
Reclassification of accumulated other comprehensive loss to income allocation	$ 500	700	$ 900
Increase in fair value of property, plant and equipment	$ 140,800	$ 145,600

Equity Investment - Schedule o

Equity Investment - Schedule of Summarized Financial Information of Unaudited Financial Statements (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Sales					$ 48,306	$ 40,457	$ 40,061
Net income	$ 49,058	$ 28,900	$ 37,241	$ 24,338	139,537	88,667	96,892
Current assets	242,543				242,543	91,396
Current liabilities	148,746				148,746	120,549
Ciner Wyoming
Schedule of Equity Method Investments [Line Items]
Sales					486,759	497,340	475,187
Gross profit					104,053	114,202	114,232
Net income					108,357	91,523	$ 91,596
Current assets	138,080				138,080	180,433
Noncurrent assets	252,743				252,743	228,002
Current liabilities	64,012				64,012	56,219
Noncurrent liabilities	$ 109,921				$ 109,921	$ 148,401

Plant and Equipment, Net (Detai

Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Plant and equipment at cost	$ 6,865	$ 6,865
Less: accumulated depreciation	(5,881)	(5,517)
Total plant and equipment, net	$ 984	$ 1,348

Plant and Equipment, Net - Addi

Plant and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation expense on plant and equipment									$ 400	$ 400	$ 800
Asset impairments	$ 18,038	$ 0	$ 0	$ 242	$ 1,189	$ 0	$ 0	$ 1,778	$ 18,280	$ 2,967	15,861
Property, Plant and Equipment
Property, Plant and Equipment [Line Items]
Asset impairments											$ 2,000

Mineral Rights, Net (Detail)

Mineral Rights, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	$ 1,215,318	$ 1,233,609
Accumulated Depletion	(472,206)	(455,190)
Net Book Value	743,112	778,419
Coal Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	1,164,845	1,170,104
Accumulated Depletion	(451,210)	(436,964)
Net Book Value	713,635	733,140
Aggregate Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	24,920	37,942
Accumulated Depletion	(11,814)	(9,602)
Net Book Value	13,106	28,340
Oil And Gas Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	12,395	12,395
Accumulated Depletion	(7,632)	(7,158)
Net Book Value	4,763	5,237
Other Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	13,158	13,168
Accumulated Depletion	(1,550)	(1,466)
Net Book Value	$ 11,608	$ 11,702

Mineral Rights, Net - Additiona

Mineral Rights, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Proceeds from sale of assets									$ (2,449)	$ (1,151)	$ (62,117)
Gain (loss) on asset sales	$ 1,622	$ 0	$ 168	$ 651	$ 178	$ 154	$ 3,184	$ 29	2,441	3,545	29,068
Total depletion and amortization expense on mineral interests									17,000	20,100	27,800
Appalachian Basin
Proceeds from sale of assets											36,400
Gain (loss) on asset sales											18,600
Texas, Georgia, Tennessee
Gain (loss) on asset sales											1,500
Proceeds from Sale of Hard Mineral Reserves											10,000
Other Mineral Rights
Proceeds from sale of assets									2,400	(1,000)	(17,300)
Gain (loss) on asset sales									$ 2,400	$ 3,500	$ 8,600

Mineral Rights, Net Schedule of

Mineral Rights, Net Schedule of Impairment Expense (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Asset impairments	$ 18,038	$ 0	$ 0	$ 242	$ 1,189	$ 0	$ 0	$ 1,778			$ 18,280	$ 2,967	$ 15,861
Coal Mineral Rights
Property, Plant and Equipment [Line Items]
Asset impairments	5,000								$ 8,200	$ 3,800	5,259	595	12,088
Fair value of impaired assets	0								$ 0	$ 4,000	0		0
Oil And Gas Mineral Rights
Property, Plant and Equipment [Line Items]
Asset impairments											0	0	36
Mining Properties and Mineral Rights
Property, Plant and Equipment [Line Items]
Asset impairments											18,280	2,967	13,801
Aggregate Mineral Rights
Property, Plant and Equipment [Line Items]
Asset impairments	13,021										13,021	$ 2,372	$ 1,677
Fair value of impaired assets	$ 2,300										$ 2,300

Intangible Assets, Net - Intang

Intangible Assets, Net - Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 4,300	$ 2,000
Finite-Lived Intangible Assets, Gross	81,109	81,109
Less accumulated amortization	(38,596)	(34,289)
Total intangible assets, net	$ 42,513	$ 46,820

Intangible Assets, Net - Estima

Intangible Assets, Net - Estimated Amortization Expense (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2,019	$ 3,251
2,020	3,741
2,021	3,660
2,022	3,636
2,023	$ 3,602

Intangible Assets, Net - Addit

Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Intangible Assets [Line Items]
Amortization expense—affiliate	$ 0	$ 1,008	$ 3,185
Amortization expense	$ 4,300	$ 2,000
Contractual Rights
Intangible Assets [Line Items]
Remaining amortization period for intangibles (in years)	16 years

Debt, Net - Debt (Detail)

Debt, Net - Debt (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 02, 2017
Debt Instrument [Line Items]
Senior Note issue percentage			98.75%
Principal balance	$ 687,138,000	$ 827,844,000
Net unamortized debt discount	(1,266,000)	(1,661,000)
Net unamortized debt issuance costs	(13,114,000)	(16,835,000)
Total debt	672,758,000	809,348,000
Less - current portion of long term debt	115,184,000	79,740,000
Total long-term debt, net	557,574,000	729,608,000
NRP LP | 10.5% senior notes, with semi-annual interest payments in March and September, maturing March 2022 [Member]
Debt Instrument [Line Items]
Principal balance	$ 345,638,000	345,638,000
NRP LP | Senior Notes Due Two Zero Two Two [Member]
Debt Instrument [Line Items]
Interest rate	10.50%
Senior Notes, Face Amount	$ 345,638,000
NRP LP | 9.125% senior notes, with semi-annual interest payments in April and October, maturing October 2018
Debt Instrument [Line Items]
Interest rate	9.125%
Senior Notes, Face Amount	$ 425,000,000
Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Floating rate revolving credit facility	100,000,000
Principal balance	$ 0	60,000,000
Opco | 4.91% senior notes, with semi-annual interest payments in June and December, with annual principal payments in June, maturing in June 2018
Debt Instrument [Line Items]
Interest rate	4.91%
Principal balance	$ 0	4,586,000
Opco | 8.38% senior notes, with semi-annual interest payments in March and September, with annual principal payments in March, maturing in March 2019 [Member]
Debt Instrument [Line Items]
Interest rate	8.38%
Principal balance	$ 21,319,000	42,670,000
Opco | 5.05% senior notes, with semi-annual interest payments in January and July, with annual principal payments in July, maturing in July 2020 [Member]
Debt Instrument [Line Items]
Interest rate	5.05%
Principal balance	$ 15,290,000	22,946,000
Opco | 5.55% senior notes, with semi-annual interest payments in June and December, with annual principal payments in June, maturing in June 2023 [Member]
Debt Instrument [Line Items]
Interest rate	5.55%
Principal balance	$ 13,414,000	16,115,000
Opco | 4.73% senior notes, with semi-annual interest payments in June and December, with scheduled principal payments beginning December 2014, maturing in December 2023 [Member]
Debt Instrument [Line Items]
Interest rate	4.73%
Principal balance	$ 37,195,000	44,693,000
Opco | 5.82% senior notes, with semi-annual interest payments in March and September, with annual principal payments in March, maturing in March 2024 [Member]
Debt Instrument [Line Items]
Interest rate	5.82%
Principal balance	$ 89,529,000	104,520,000
Opco | 8.92% senior notes, with semi-annual interest payments in March and September, with scheduled principal payments beginning March 2014, maturing in March 2024 [Member]
Debt Instrument [Line Items]
Interest rate	8.92%
Principal balance	$ 27,185,000	31,733,000
Opco | 5.03% senior notes, with semi-annual interest payments in June and December, with scheduled principal payments beginning December 2014, maturing in December 2026 [Member]
Debt Instrument [Line Items]
Interest rate	5.03%
Principal balance	$ 107,013,000	120,547,000
Opco | 5.18% senior notes, with semi-annual interest payments in June and December, with scheduled principal payments beginning December 2014, maturing in December 2026 [Member]
Debt Instrument [Line Items]
Interest rate	5.18%
Principal balance	$ 30,555,000	34,396,000
Opco | Utility Local Improvement Obligation Due March Two Zero Two One [Member]
Debt Instrument [Line Items]
Interest rate	5.31%
Senior Notes Offering Price Two [Member] | NRP LP | Senior Notes Due Two Zero Two Two [Member]
Debt Instrument [Line Items]
Floating rate revolving credit facility	$ 240,638,000
Senior Note issue percentage	100.00%
Senior Notes Offering Price Two [Member] | NRP LP | 9.125% senior notes, with semi-annual interest payments in April and October, maturing October 2018
Debt Instrument [Line Items]
Floating rate revolving credit facility	$ 125,000,000
Senior Note issue percentage	99.50%
Senior Notes Offering Price One [Member] | NRP LP | Senior Notes Due Two Zero Two Two [Member]
Debt Instrument [Line Items]
Floating rate revolving credit facility	$ 105,000,000
Senior Note issue percentage	98.75%
Senior Notes Offering Price One [Member] | NRP LP | 9.125% senior notes, with semi-annual interest payments in April and October, maturing October 2018
Debt Instrument [Line Items]
Floating rate revolving credit facility	$ 300,000,000
Senior Note issue percentage	99.007%
Revolving Credit Facility | Opco
Debt Instrument [Line Items]
Secured Debt		$ 553,900,000
Debt Instrument, Interest Rate During Period	6.23%	5.32%
Net unamortized debt issuance costs	$ (1,700,000)	$ (4,600,000)
Debt Instrument, Collateral Amount	548,900,000
Discontinued Operations, Held-for-sale | Revolving Credit Facility | Opco
Debt Instrument [Line Items]
Debt Instrument, Collateral Amount	$ 95,700,000	$ 95,700,000

Debt, Net - Additional Informat

Debt, Net - Additional Information (Detail)	Mar. 02, 2017USD ($)	Mar. 31, 2019USD ($)	Jun. 30, 2017	Dec. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jul. 31, 2013	Jan. 31, 2013
Debt Instrument [Line Items]
Senior Note issue percentage	98.75%
Debt issuance cost capitalized				$ 13,114,000	$ 16,835,000
Principal balance				687,138,000	827,844,000
Debt Instrument, Percentage of Principal Eligible for Redemption	35.00%
Debt Instrument, Discount on Debt Issuance, as a Percent	1.25%
Debt Instrument, Net Redemption Premium, Percent	5.813%
Debt Instrument, Redemption Premium Above Par, Percentage	4.563%
Debt Instrument, Fee on Redemption, Percent	1.25%
Long-term Debt				672,758,000	809,348,000
Senior Notes due 2022
Debt Instrument [Line Items]
Principal balance				$ 334,024,000	330,404,000
Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Rate of senior notes	10.50%
Senior Notes, Face Amount	$ 346,000,000
Proceeds from Issuance of Secured Debt	$ 105,000,000
Debt Instrument Redemption Price Percentage Of Principal Remaining After Redemption	65.00%
Debt Instrument Redemption Price At Change Of Control Event As Percentage Of Principal Amount	101.00%
Senior Notes due 2018 | Senior Notes
Debt Instrument [Line Items]
Senior Notes, Face Amount	$ 241,000,000
Debt Instrument, Redemption Premium Above Par, Percentage			4.563%
Ciner Wyoming
Debt Instrument [Line Items]
Percentage of partnership interest owned (percent)				49.00%			49.00%	48.51%
Ciner Wyoming | Revolving Credit Facility
Debt Instrument [Line Items]
Percentage of partnership interest owned (percent)				49.00%
NRP LP | 9.125% senior notes, with semi-annual interest payments in April and October, maturing October 2018
Debt Instrument [Line Items]
Rate of senior notes				9.125%
Senior Notes, Face Amount				$ 425,000,000
NRP LP | Senior Notes
Debt Instrument [Line Items]
Rate of senior notes				10.50%
Long-term Debt				$ 344,400,000	$ 344,000,000
Opco
Debt Instrument [Line Items]
Ratio of consolidated EBITDDA to consolidated fixed charges				3.5
Percentage of consolidated net tangible assets debt of subsidiaries not permitted to exceed				10.00%
Opco | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period				6.23%	5.32%
Debt issuance cost capitalized				$ 1,700,000	$ 4,600,000
Debt Instrument, Asset Sales Proceeds, Required to Repay Outstanding Debt, Percent				75.00%
Ratio of consolidated EBITDDA to consolidated fixed charges				3.5
Secured Debt					553,900,000
Debt Instrument, Collateral Amount				$ 548,900,000
Commitment fee (as a percent)				0.50%
Opco | 8.38% senior notes, with semi-annual interest payments in March and September, with annual principal payments in March, maturing in March 2019 [Member]
Debt Instrument [Line Items]
Rate of senior notes				8.38%
Principal balance				$ 21,319,000	42,670,000
Opco | 8.92% senior notes, with semi-annual interest payments in March and September, with scheduled principal payments beginning March 2014, maturing in March 2024 [Member]
Debt Instrument [Line Items]
Rate of senior notes				8.92%
Principal balance				$ 27,185,000	31,733,000
Opco | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Covenant, Asset Sales				$ 300,000,000
Debt Instrument, Asset Sales Proceeds, Required to Repay Outstanding Debt, Percent				25.00%
Principal balance				$ 341,500,000	422,200,000
Principal payments on its senior notes				(80,700,000)	(80,800,000)	$ (82,900,000)
Restricted Cash				$ 55,000,000
Partnership leverage ratio				3.75
Additional interest accrue				2.00%
Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Floating rate revolving credit facility				$ 100,000,000
Debt Instrument, Asset Sales Proceeds, Required to Repay Outstanding Debt, Percent				75.00%
Principal balance				$ 0	60,000,000
Line of Credit Facility, Remaining Borrowing Capacity				$ 100,000,000
Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty Two [Member]
Debt Instrument [Line Items]
Distribution amount (in dollars per share) | $ / shares				$ 0.45
Opco | Maximum
Debt Instrument [Line Items]
Ratio of consolidated indebtedness to consolidated EBITDDA				4
Opco | Federal Funds Rate [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate (percent)				0.50%
Opco | London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate (percent)				1.00%
Opco | London Interbank Offered Rate (LIBOR) [Member] | Maximum | Revolving Credit Facility Basis Spread Condition One [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Additional basis spread (percent)				3.50%
Opco | London Interbank Offered Rate (LIBOR) [Member] | Maximum | Revolving Credit Facility Basis Spread Condition Two [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Additional basis spread (percent)				4.50%
Opco | London Interbank Offered Rate (LIBOR) [Member] | Minimum | Revolving Credit Facility Basis Spread Condition One [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Additional basis spread (percent)				2.50%
Opco | London Interbank Offered Rate (LIBOR) [Member] | Minimum | Revolving Credit Facility Basis Spread Condition Two [Member] | Revolving Credit Facility
Debt Instrument [Line Items]
Additional basis spread (percent)				3.50%
Debt Instrument, Redemption, Period Two | Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	105.25%
Debt Instrument, Redemption, Period Three | Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	102.625%
Debt Instrument, Redemption, Period Four [Member] | Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	100.00%
Debt Instrument, Redemption, Period One | Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	110.50%
Restricted Payments Covenant [Member] | Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Covenant, Consolidated Leverage Ratio, Maximum	4
Debt Instrument, Covenant, Dividend Payment Restriction, Percent	50.00%
Debt Incurrence Covenant [Member] | Senior Notes due 2022 | Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Covenant, Consolidated Leverage Ratio, Maximum	3
Debt Instrument, Covenant, Debt Limit Numerator	$ 150,000,000
Dividend at or Below $0.45 per Share [Member] | Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty Two [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant, Maximum Leverage Ratio	4			4
Dividend Above $0.45 per Share [Member] | Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty Two [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant, Maximum Leverage Ratio				3
Subsequent Event | Opco | Senior Notes
Debt Instrument [Line Items]
Principal payments on its senior notes		$ (49,000,000)
Discontinued Operations, Held-for-sale | Opco | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Collateral Amount				$ 95,700,000	$ 95,700,000

Debt, Net - Principal Payments

Debt, Net - Principal Payments Due (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
2,018	$ 116,125
2,019	46,436
2,020	39,634
2,021	385,272
2,022	39,634
Thereafter	60,037
Principal Payments	687,138
Long-term Debt	672,758	$ 809,348
NRP LP | Senior Notes
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	345,638
2,022	0
Thereafter	0
Principal Payments	$ 345,638
Rate of senior notes	10.50%
Long-term Debt	$ 344,400	$ 344,000
Opco | Senior Notes
Debt Instrument [Line Items]
2,018	116,125
2,019	46,436
2,020	39,634
2,021	39,634
2,022	39,634
Thereafter	60,037
Principal Payments	341,500
Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	100,000
Opco | Revolving Credit Facility
Debt Instrument [Line Items]
2,018	0
2,019	0
2,020	0
2,021	0
2,022	0
Thereafter	0
Principal Payments	$ 0

Fair Value Measurements - Debt

Fair Value Measurements - Debt and Contracts Receivable (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	$ 0	$ 0
Carrying Value	687,138,000	827,844,000
Receivables, Fair Value Disclosure	40,776,000	43,826,000
Embedded Derivative, Fair Value of Embedded Derivative Liability	0	0
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Receivables, Fair Value Disclosure	34,704,000	30,517,000
Senior Notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	334,024,000	330,404,000
Senior Notes due 2022 | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	356,871,000	366,376,000
Opco Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	338,734,000	418,944,000
Opco Senior Notes | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	352,599,000	447,538,000
Opco Revolving Credit Facility And Term Loan Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	0	60,000,000
Opco Revolving Credit Facility And Term Loan Facility | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	$ 0	$ 60,000,000

Related Party Transactions - Su

Related Party Transactions - Summary of Reimbursements (Detail) - USD ($) $ in Thousands	May 09, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Revenues		$ 63,935	$ 58,207	$ 69,451	$ 59,478	$ 64,927	$ 58,406	$ 58,015	$ 61,432	$ 251,071	$ 242,780	$ 250,176
Operating and maintenance expenses—affiliates										11,615	8,112	9,153
General and administrative—affiliates										3,658	4,989	3,591
Operating Expenses										85,974	69,766	98,087
Foresight Energy Lp
Related Party Transaction [Line Items]
Revenues										54,595	70,489	63,355
Cline Affiliates
Related Party Transaction [Line Items]
Rate of interest in the partnerships general partner	31.00%
Operating and maintenance expenses—affiliates										0	452	1,347
Operating Expenses										1,761	1,066	0
Cline Affiliates | Foresight Energy Lp
Related Party Transaction [Line Items]
Operating Expenses										1,761	1,518	1,347
Affiliated Entity | Western Pocahontas Properties and Quintana Minerals Corporation
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates										6,170	6,184	8,119
General and administrative—affiliates										3,658	4,989	3,591
Transportation and Processing | Foresight Energy Lp
Related Party Transaction [Line Items]
Revenues										23,818	14,510	0
Transportation and processing services—affiliate | Foresight Energy Lp
Related Party Transaction [Line Items]
Revenue from Related Parties										$ 0	$ 6,012	$ 19,336

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	May 09, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Revenues		$ 63,935	$ 58,207	$ 69,451	$ 59,478	$ 64,927	$ 58,406	$ 58,015	$ 61,432	$ 251,071	$ 242,780	$ 250,176
Lease receivable, next year		5,000								5,000
Quarterly lease receivable		1,250								1,250
Operating and maintenance expense										85,974	69,766	98,087
Operating and maintenance expenses—affiliates										11,615	8,112	9,153
General and administrative—affiliates										3,658	4,989	3,591
Amount payable to related parties		1,866				490				1,866	490
Accounts receivable—affiliates		34				161				34	161
Deferred Revenue, Revenue Recognized										20,242
Quintana Minerals
Related Party Transaction [Line Items]
Amount payable to related parties		500				400				500	400
Western Pocahontas Properties
Related Party Transaction [Line Items]
Amount payable to related parties		1,400				100				1,400	100
Cline Affiliates
Related Party Transaction [Line Items]
Related Party Transaction, Rate	31.00%
Operating and maintenance expense										1,761	1,066	0
Operating and maintenance expenses—affiliates										0	452	1,347
Western Pocahontas Properties and Quintana Minerals Corporation | Affiliated Entity
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates										6,170	6,184	8,119
General and administrative—affiliates										3,658	4,989	3,591
Foresight Energy Lp
Related Party Transaction [Line Items]
Revenues										54,595	70,489	63,355
Foresight Energy Lp | Cline Affiliates
Related Party Transaction [Line Items]
Operating and maintenance expense										1,761	1,518	1,347
Foresight Energy Lp | Coal Sales
Related Party Transaction [Line Items]
Revenues										30,777	28,763	0
Revenue from Related Parties										0	21,204	44,019
Sugar Camp
Related Party Transaction [Line Items]
Lease receivable, year two		5,000								5,000
Lease receivable, year three		5,000								5,000
Lease receivable, year four		5,000								5,000
Lease receivable, year five		5,000								5,000
Projected remaining payments		66,495				71,452				66,495	71,452
Unearned income		25,058				28,366				25,058	28,366
Corsa
Related Party Transaction [Line Items]
Revenue from Related Parties										484	1,300	2,200
Accounts receivable—affiliates						200					200
Western Pocahontas Properties Limited Partnership | Affiliated Entity
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates										5,400	1,500	700
Other assets—affiliate						200					200
Quinwood Coal Company
Related Party Transaction [Line Items]
Deferred Revenue, Revenue Recognized											900
Discontinued Operations, Held-for-sale | Quintana Minerals
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates										1,000	1,400	$ 3,100
Amount payable to related parties		$ 100				$ 100				$ 100	$ 100

Major Customers (Detail)

Major Customers (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Revenues	$ 63,935	$ 58,207	$ 69,451	$ 59,478	$ 64,927	$ 58,406	$ 58,015	$ 61,432	$ 251,071	$ 242,780	$ 250,176
Foresight Energy Lp
Concentration Risk [Line Items]
Revenues									$ 54,595	$ 70,489	$ 63,355
Sales Revenue | Customer Concentration Risk | Foresight Energy Lp
Concentration Risk [Line Items]
Concentration risk, percentage									21.70%	29.00%	25.30%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended	36 Months Ended
	Oct. 31, 2018	Dec. 31, 2018	Dec. 31, 2015	Jul. 31, 2013	Jan. 31, 2013
Anadarko Holding Company
Commitments And Contingencies [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High					$ 50
Ciner Wyoming | Anadarko Holding Company
Commitments And Contingencies [Line Items]
Equity Investment Contingent Consideration Paid			$ 11.5
OCI LP | Ciner Wyoming
Commitments And Contingencies [Line Items]
Percentage of partnership interest owned (percent)					1.00%
Ciner Wyoming
Commitments And Contingencies [Line Items]
Percentage of partnership interest owned (percent)		49.00%		49.00%	48.51%
Pending Litigation | Minimum | Anadarko Holding Company
Commitments And Contingencies [Line Items]
Minimum deficiency payments		$ 0
Pending Litigation | Maximum | Anadarko Holding Company
Commitments And Contingencies [Line Items]
Minimum deficiency payments		40
Settled Litigation [Member] | Lawsuit Against Hillsboro Energy LLC
Commitments And Contingencies [Line Items]
Proceeds from Legal Settlements	$ 25
Damages sought, value		30
Litigation Settlement, Amount Awarded from Other Party	$ 11
Loss Contingency, Forfeiture of Recoupable Lease Balance in Settlement		$ 37.4

Unit-Based Compensation Additio

Unit-Based Compensation Additional Information (Details) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeitures during the period (in shares)	(2)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	17
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	75
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	56	0
Vesting period of Grants (in years)	3 years
Grant date fair value	$ 2.2
Unaccrued Cost Associated With Outstanding Grants And Related Distribution Equivalent Rights	1.2
Board Members [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value	0.6
Compensation expense	0.4
Operating Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	0.1
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 1

Unit-Based Compensation Summary

Unit-Based Compensation Summary of Activity in Outstanding Grants (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	2 years 1 month 15 days
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	800,000
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Vesting period of Grants (in years)	3 years
Unaccrued Cost Associated With Outstanding Grants And Related Distribution Equivalent Rights	$ 1.2
Grant date fair value	$ 2.2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 29.10	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding grants at beginning of period (in shares)	0
Grants during the period (in shares)	75,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 29.16
Grants vested and paid during the period (in shares)	(17,000)
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$ 31.24
Forfeitures during the period (in shares)	(2,000)
Outstanding grants at the end of the period (in shares)	56,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 0
Board Members [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value	$ 0.6
Compensation expense	0.4
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	1
Operating Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 0.1

Supplemental Quarterly Inform_3

Supplemental Quarterly Information (Unaudited) - Selected Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Mar. 02, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2016
Revenues		$ 63,935	$ 58,207	$ 69,451	$ 59,478	$ 64,927	$ 58,406	$ 58,015	$ 61,432	$ 251,071	$ 242,780	$ 250,176
Gain on litigation settlement		25,000	0	0	0					25,000	0	0
Gain (loss) on asset sales		1,622	0	168	651	178	154	3,184	29	2,441	3,545	29,068
Asset impairments		18,038	0	0	242	1,189	0	0	1,778	18,280	2,967	15,861
Income from operations		52,093	43,346	52,863	44,236	47,861	43,052	47,522	38,124	192,538	176,559	181,157
Net income		49,058	28,900	37,241	24,338					139,537	88,667	96,892
Debt modification expense						0	0	132	7,807	0	7,939	0
Loss on extinguishment of debt						0	0		0	0	4,107	0
Net income from continuing operations		35,092	25,853	35,129	26,286	28,665	23,079	23,153	7,588	122,360	82,485	90,626
Income (loss) from discontinued operations		13,966	2,688	2,981	(1,948)	2,042	2,987	2,837	(1,684)	17,687	6,182	6,266
Net income		49,058	28,541	38,110	24,338	30,707	26,066	25,990	5,904	140,047	88,667	96,892
Net income attributable to common unitholders and general partner		$ 41,558	$ 21,400	$ 29,741	$ 16,838	$ 22,942	$ 18,416	$ 18,452	$ 3,404	$ 109,537	$ 63,214	$ 96,892
Income from continuing operations per common unit (basic)		$ 2.21	$ 1.50	$ 2.14	$ 1.50	$ 1.67	$ 1.24	$ 1.25	$ 0.41	$ 7.35	$ 4.57	$ 7.28
Income from continuing operations per common unit (diluted)		1.69	1.18	1.57	1.16	1.18	0.94	1.01	0.50	5.90	3.68	7.28
Basic net income per common unit		3.33	1.71	2.38	1.35	1.84	1.48	1.47	0.28	8.77	5.06	7.78
Diluted net income per common unit		$ 2.36	$ 1.30	$ 1.71	$ 1.08	$ 1.26	$ 1.07	$ 1.13	$ 0.28	$ 6.76	$ 3.96	$ 7.78
Weighted average number of common units outstanding (basic)		12,247	12,246	12,246	12,238	12,232	12,232	12,232	12,232	12,244	12,232	12,232
Weighted average number of common units outstanding (diluted)		20,394	21,840	21,383	22,125	23,874	23,980	22,459	14,945	20,234	21,950	12,232
Debt Instrument, Redemption Premium Above Par, Percentage	4.563%
Senior Notes | Senior Notes due 2018
Loss on extinguishment of debt								$ (4,107)
Senior Notes, Face Amount	$ 241,000
Debt Instrument, Redemption Premium Above Par, Percentage								4.563%
Discontinued Operations, Held-for-sale
Gain (loss) on asset sales		$ 13,100								$ 13,100
Disposal Group, Including Discontinued Operation, Consideration		$ 205,000								$ 205,000			$ 116,100
Previously Reported
Revenues			$ 94,855	$ 109,860	$ 86,630	$ 100,822	$ 93,116	$ 91,570	$ 88,653		$ 374,161
Gain (loss) on asset sales			163	210	660	280	171	3,361	44		3,856
Asset impairments					242	1,253			1,778		3,031
Income from operations			46,066	55,878	42,322	49,998	46,531	50,404	37,042		183,975
Net income			28,900	37,241	24,338
Debt modification expense								132	7,807		7,939
Loss on extinguishment of debt											4,107
Net income from continuing operations			28,565	38,144	24,352	30,741	26,499	25,857	6,111		89,208
Income (loss) from discontinued operations			(24)	(34)	(14)	(34)	(433)	133	(207)		(541)
Net income			28,541	38,110	24,338	30,707	26,066	25,990	5,904		88,667
Net income attributable to common unitholders and general partner			$ 21,400	$ 29,741	$ 16,838	$ 22,942	$ 18,416	$ 18,452	$ 3,404		$ 63,214
Income from continuing operations per common unit (basic)			$ 1.71	$ 2.38	$ 1.35	$ 1.84	$ 1.51	$ 1.46	$ 0.30		$ 5.11
Income from continuing operations per common unit (diluted)			1.30	1.71	1.08	1.26	1.08	1.13	0.30		3.98
Basic net income per common unit			1.71	2.38	1.35	1.84	1.48	1.47	0.28		5.06
Diluted net income per common unit			$ 1.30	$ 1.71	$ 1.08	$ 1.26	$ 1.07	$ 1.13	$ 0.28		$ 3.96
Weighted average number of common units outstanding (basic)			12,246	12,246	12,238	12,232	12,232	12,232	12,232		12,232
Weighted average number of common units outstanding (diluted)			21,840	21,383	22,125	23,874	23,980	22,459	14,945		21,950
Previously Reported | Senior Notes | Senior Notes due 2018
Loss on extinguishment of debt								$ (4,107)
Restatement Adjustment
Revenues			$ (36,648)	$ (40,409)	$ (27,152)	$ (35,895)	$ (34,710)	(33,555)	$ (27,221)		$ (131,381)
Gain (loss) on asset sales			(163)	(42)	(9)	(102)	(17)	(177)	(15)		(311)
Asset impairments					0	(64)			0		(64)
Income from operations			(2,720)	(3,015)	1,914	(2,137)	(3,479)	(2,882)	1,082		(7,416)
Net income			0	0	0
Debt modification expense								0	0		0
Loss on extinguishment of debt											0
Net income from continuing operations			(2,712)	(3,015)	1,934	(2,076)	(3,420)	(2,704)	1,477		(6,723)
Income (loss) from discontinued operations			2,712	3,015	(1,934)	2,076	3,420	2,704	(1,477)		6,723
Net income			0	0	0	0	0	0	0		0
Net income attributable to common unitholders and general partner			$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		$ 0
Income from continuing operations per common unit (basic)			$ (0.22)	$ (0.24)	$ 0.15	$ (0.17)	$ (0.27)	$ (0.22)	$ 0.12		$ (0.54)
Income from continuing operations per common unit (diluted)			(0.12)	(0.14)	0.09	(0.09)	(0.14)	(0.12)	0.10		(0.30)
Basic net income per common unit			0	0	0	0	0	0	0		0
Diluted net income per common unit			$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0		$ 0
Weighted average number of common units outstanding (basic)			0	0	0	0	0	0	0		0
Weighted average number of common units outstanding (diluted)			0	0	0	0	0	0	0		0
Restatement Adjustment | Senior Notes | Senior Notes due 2018
Loss on extinguishment of debt								$ 0

Uncategorized Items - nrp-20181

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 70,466,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	40,244,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(10,544,000)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	51,773,000
General Partner [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	1,409,000
Common Stock [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	69,057,000
Partners Capital Excluding Noncontrolling Interest [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 70,466,000