Natural Resource Partners (NRP) 10-Q 9 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 01, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Period End Date	Mar. 31, 2018
Document Fiscal Period Focus	Q1
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 Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		12,245,920

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 21,152	$ 29,827
Accounts receivable, net	55,651	47,026
Accounts receivable—affiliates	94	161
Inventory	8,071	7,553
Prepaid expenses and other	3,088	5,838
Current assets of discontinued operations	991	991
Total current assets	89,047	91,396
Land	24,809	25,247
Plant and equipment, net	47,237	46,170
Mineral rights, net	878,845	883,885
Intangible assets, net	48,769	49,554
Equity in unconsolidated investment	241,679	245,433
Long-term contracts receivable	40,331	40,776
Other assets	6,489	6,547
Other assets—affiliate	0	156
Total assets	1,377,206	1,389,164
Current liabilities:
Accounts payable	5,911	6,957
Accounts payable—affiliates	2,093	562
Accrued liabilities	11,409	16,890
Accrued liabilities—affiliates	0	515
Accrued interest	5,706	15,484
Current portion of deferred revenue	1,554	0
Current portion of long-term debt, net	79,723	79,740
Current liabilities of discontinued operations	3	401
Total current liabilities	106,399	120,549
Deferred revenue	14,622	100,605
Long-term debt, net	724,854	729,608
Other non-current liabilities	2,492	2,808
Other non-current liabilities—affiliate	0	346
Total liabilities	848,367	953,916
Commitments and contingencies	0	0
Class A Convertible Preferred Units (250,000 and 258,844 units issued and outstanding at March 31, 2018 and December 31, 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 (12,245,920 and 12,232,006 units issued and outstanding at March 31, 2018 and December 31, 2017, respectively)	301,344	199,851
General partner’s interest	3,924	1,857
Warrant holders’ interest	66,816	66,816
Accumulated other comprehensive loss	(4,438)	(3,313)
Total partners’ capital	367,646	265,211
Non-controlling interest	(3,394)	(3,394)
Total capital	364,252	261,817
Total liabilities and capital	$ 1,377,206	$ 1,389,164

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common units outstanding (in shares)	12,245,920	12,232,006
Common units issued (in shares)	12,245,920	12,232,006
Preferred units issued (in shares)	250,000	258,844
Preferred units outstanding (in shares)	250,000	258,844
Preferred unit par value per unit	$ 1,000	$ 1,000
Preferred unit liquidation preference per unit	$ 1,500	$ 1,500

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Revenues and other income
Revenues and other income	$ 88,366		$ 88,653
Gain on asset sales, net	660		44
Total revenues and other income	89,026		88,697
Operating expenses
Operating and maintenance expenses	29,968		29,628
Operating and maintenance expenses—affiliates	2,465		2,555
Depreciation, depletion and amortization	7,957		9,724
Amortization expense—affiliate	0		768
General and administrative	3,405		6,078
General and administrative—affiliates	931		1,124
Asset impairments	242		1,778
Total operating expenses	44,968		51,655
Income from operations	44,058		37,042
Other income (expense)
Interest expense	(18,006)		(23,141)
Debt modification expense	0		(7,807)
Interest income	36		17
Other expense, net	(17,970)		(30,931)
Net income from continuing operations	26,088		6,111
Loss from discontinued operations	(14)		(207)
Net income	26,074	[1]	5,904
Income attributable to preferred unitholders	(7,500)		(2,500)
Net income attributable to common unitholders and general partner	18,574		3,404
Net income attributable to common unitholders	18,203		3,404
Net income attributable to the general partner	$ 371		$ 0
Income from continuing operations per common unit
Basic (in dollars per share)	$ 1.49		$ 0.30
Diluted (in dollars per share)	1.16		0.30
Net income per common unit
Basic (in dollars per share)	1.49		0.28
Diluted (in dollars per share)	$ 1.15		$ 0.28
Add: comprehensive loss from unconsolidated investment and other	$ (1,125)		$ (1,132)
Comprehensive income	24,949		4,772
Coal Royalty and Other
Revenues and other income
Revenues and other income	45,973		34,994
Coal royalty and other—affiliates	237		11,505
Construction Aggregates
Revenues and other income
Revenues and other income	26,424		25,483
Gain on asset sales, net	9
Soda Ash
Revenues and other income
Revenues and other income	9,621		10,294
Transportation and Processing | Coal Royalty and Other
Revenues and other income
Revenues and other income	5,383		0
Transportation and Processing - Affiliates | Coal Royalty and Other
Revenues and other income
Coal royalty and other—affiliates	0		4,639
Road construction and asphalt paving services | Construction Aggregates
Revenues and other income
Revenues and other income	$ 728		$ 1,738
[1]	Net income includes $7.5 million attributable to Preferred Unitholders that accumulated during the period, of which $7.4 million is allocated to the common unitholders and $0.2 million is allocated to the general partner.

Consolidated Statements of Part

Consolidated Statements of Partners' Capital - 3 months ended Mar. 31, 2018 - 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, 2017				12,232
Balance, beginning of period at Dec. 31, 2017		$ 261,817	$ 1,857	$ 199,851	$ 66,816	$ (3,313)	$ 265,211	$ (3,394)
Net Income	[1]	26,074	521	$ 25,553			26,074
Distributions to unitholders										$ (5,505)		$ (112)	$ (5,617)	$ (5,617)	$ (7,765)	$ (155)	$ (7,610)	$ (7,765)
Issuance of unit-based awards (units)				14
Issuance of unit-based awards		410		$ 410			410
Unit-based awards amortization and vesting		197		$ 197			197
Comprehensive income from unconsolidated investment and other		24,949	8			(1,125)	(1,117)
Comprehensive loss from unconsolidated investment and other		(1,117)
Balance, end of period (in shares) at Mar. 31, 2018				12,246
Balance, end of period at Mar. 31, 2018		364,252	$ 3,924	$ 301,344	$ 66,816	$ (4,438)	$ 367,646	$ (3,394)
Income attributable to preferred unitholders		7,500							$ 7,400		$ 200
Comprehensive loss from unconsolidated investment and other		$ (1,125)
[1]	Net income includes $7.5 million attributable to Preferred Unitholders that accumulated during the period, of which $7.4 million is allocated to the common unitholders and $0.2 million is allocated to the general partner.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income	$ 26,074	$ 5,904
Adjustments to reconcile net income to net cash provided by operating activities of continuing operations:
Depreciation, depletion and amortization	7,957	9,724
Amortization expense—affiliate	0	768
Distributions from unconsolidated investment	10,153	12,250
Equity earnings from unconsolidated investment	(9,621)	(10,294)
Gain on asset sales, net	(660)	(44)
Debt modification expense	0	7,807
Loss from discontinued operations	14	207
Asset impairments	242	1,778
Unit-based compensation expense	792	257
Amortization of debt issuance costs and other	771	973
Other, net—affiliates	(190)	135
Change in operating assets and liabilities:
Accounts receivable	(5,189)	(1,267)
Accounts receivable—affiliates	67	(196)
Accounts payable	(845)	986
Accounts payable—affiliates	1,531	256
Accrued liabilities	(5,169)	(7,948)
Accrued liabilities—affiliates	(515)	0
Accrued interest	(9,777)	(271)
Deferred revenue	2,346	1,077
Deferred revenue—affiliates	0	(2,897)
Other items, net	2,230	1,284
Net cash provided by operating activities of continuing operations	20,211	20,489
Net cash used in operating activities of discontinued operations	(412)	(284)
Net cash provided by operating activities	19,799	20,205
Cash flows from investing activities:
Distributions from unconsolidated investment in excess of cumulative earnings	2,097	0
Proceeds from sale of assets	687	(387)
Return of long-term contract receivable	487	0
Return of long-term contract receivable—affiliate	0	414
Acquisition of plant and equipment and other	(3,444)	(2,095)
Net cash used in investing activities of continuing operations	(173)	(2,068)
Net cash provided by investing activities of discontinued operations	0	29
Net cash used in investing activities	(173)	(2,039)
Cash flows from financing activities:
Proceeds from issuance of preferred units and warrants, net	0	242,100
Proceeds from issuance of 2022 Senior Notes, net	0	103,688
Borrowings on credit facility	35,000	0
Repayments of loans	(40,800)	(251,010)
Contributions to discontinued operations	(412)	(255)
Debt issue costs and other	(275)	(34,755)
Net cash provided by (used in) financing activities of continuing operations	(28,713)	54,153
Net cash provided by financing activities of discontinued operations	412	255
Net cash provided by (used in) financing activities	(28,301)	54,408
Net increase (decrease) in cash and cash equivalents	(8,675)	72,574
Cash and cash equivalents at beginning of period	29,827	40,371
Cash and cash equivalents at end of period	21,152	112,945
Cash paid during the period for interest from continuing operations	26,023	19,851
Issuance of 2022 Senior Notes in exchange for 2018 Senior Notes	0	240,638
General Partner
Cash flows from financing activities:
Distributions to common unitholders and general partner	(5,617)	(5,615)
Preferred Partner
Cash flows from financing activities:
Distributions to common unitholders and general partner	(7,765)	0
Class A Convertible Preferred Units
Cash flows from financing activities:
Distributions, Preferred Stock, Paid-in-Kind, Cash Redemption Payment	$ (8,844)	$ 0

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Nature of Business Natural Resource Partners L.P. (the "Partnership") engages principally in the business of owning, operating, managing and leasing a diversified portfolio of mineral properties in the United States, including interests in coal, natural soda ash from trona, construction aggregates and other natural resources. 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. Principles of Consolidation and Reporting The accompanying unaudited Consolidated Financial Statements of the Partnership have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP") for interim financial information and with Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In management's opinion, all necessary adjustments to fairly present the Partnership's results of operations, financial position and cash flows for the periods presented have been made and all such adjustments were of a normal and recurring nature. Certain reclassifications have been made to prior period amounts on the Statements of Comprehensive Income and Statements of Cash Flows to conform with current period presentation. These reclassifications had no impact on previously reported net income or cash flows from operating, investing or financing activities. Recently Adopted Accounting Standards Revenue Recognition. On January 1, 2018, NRP adopted accounting standard 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 the cumulative effect of adoption as an adjustment to 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 Construction Aggregates or Soda Ash operating segments. 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 amount, opposed to when the recoupment period for that minimum payment expired under the previous guidance. The cumulative effects of the changes made to our 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 $ 47,026 $ 3,479 $ 50,505 Liabilities Current portion of deferred revenue $ — $ 1,973 $ 1,973 Deferred revenue 100,605 (88,747 ) 11,858 Partners’ capital Common unitholders’ interest $ 199,851 $ 88,448 $ 288,299 General partner’s interest 1,857 1,805 3,662 Total partners’ capital 265,211 90,253 355,464 The impact of adoption of the new revenue standard on NRP’s Consolidated Statement of Comprehensive Income and Consolidated Balance Sheet was as follows: For the Three Months ended March 31, 2018 (In thousands) As Reported Amounts without Adoption of ASC 606 Effect of Change Coal royalty and other revenues $ 45,973 $ 47,671 $ (1,698 ) Net income from continuing operations 26,088 27,786 (1,698 ) Net income 26,074 27,772 (1,698 ) Net income per common unit (basic) 1.49 1.63 (0.14 ) Net income per common unit (diluted) 1.15 1.23 (0.08 ) As of March 31, 2018 (In thousands) As Reported Balances without Adoption of ASC 606 Effect of Change Assets Accounts receivable, net $ 55,651 $ 48,556 $ 7,095 Total assets 1,377,206 1,370,111 7,095 Liabilities and capital Current portion of deferred revenue $ 1,554 $ — $ 1,554 Deferred revenue 14,622 97,636 (83,014 ) Total liabilities 848,367 929,827 (81,460 ) Common unitholders’ interest 301,344 214,560 86,784 General partner’s interest 3,924 2,153 1,771 Total partners’ capital 367,646 279,091 88,555 Total liabilities and capital 1,377,206 1,370,111 7,095 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 31, 2018. The Partnership is currently evaluating the impact of the provisions of this guidance on its consolidated financial statements.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition Coal Royalty and Other Segment The following table represents the Partnership's Coal Royalty and Other segment revenues (including affiliates) from contracts with customers by major source: Three Months Ended March 31, 2018 (In thousands) Coal royalty revenue $ 28,691 Production lease minimum revenue 425 Minimum lease straight-line revenue 6,760 Wheelage revenue 1,974 Coal overriding royalty revenue 2,872 Aggregates royalty revenue 1,091 Oil and gas royalty revenue 2,898 Property tax revenue 1,182 Other revenue 317 Coal royalty and other revenues (including affiliates) $ 46,210 Transportation and processing services revenue (1) 2,989 Gain on asset sales, net 651 Total coal royalty and other revenues and other income (including affiliates) from contracts with customers $ 49,850 (1) Total transportation and processing services revenue on the Partnership's Consolidated Statement of Comprehensive Income was $5.4 million for the three months ended March 31, 2018 . The $3.0 million represented above relates to contracts with customers where NRP is responsible for operating and maintaining certain rail load out transportation assets. The remaining $2.4 million revenue relates to other NRP-owned infrastructure leased to and operated by third party operators accounted for under ASC 840, Leases. Discussion of the Partnership's Coal Royalty and Other segment revenues are as follows: Royalty-based leases. Approximately two-thirds of our royalty-based leases have initial terms of five to 40 years, with many lesses 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 annual or quarterly minimum amounts, which are generally recoupable out of actual production over certain time periods that generally range from three to five years. Minimum payments are either made in advance or in arrears. Historically, NRP recognized all coal and aggregates royalty revenue over the lease term based on coal or aggregates production. The recognition of revenue from minimum payments was deferred until either recoupment occurred or the recoupment period expired. 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 received from its coal and aggregates lessees resulting from production would exceed consideration received from minimum payments over the lease term. As a result of this evaluation, revenue recognition from the Partnership's royalty-based leases is now 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 as Coal royalty revenue or Aggregates royalty revenue, as applicable, over time based on production. Deferred revenue is recognized as royalty revenue either when recoupment occurs or as Production lease minimum revenue when the recoupment period expires or when NRP determines that recoupment is remote. Each reporting period, NRP will evaluate the likelihood of recoupment and recognize deferred revenue if it concludes that recoupment is remote. • 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 payment consideration amount and is recognized in Minimum lease straight-line revenue. Additionally, minimum payments due are recognized in Accounts receivable, net, with an offset to deferred revenue, and minimum payments received are recorded as deferred revenue on NRP 's Consolidated Balance Sheets. The Partnership also has overriding royalty revenue interests in certain oil and gas wells and coal reserves. Revenue from these interests is recognized over time based on when the respective commodities are sold. Wheelage. Revenue related to fees collected to transport foreign coal across property owned by the Partnership that is recognized over time per ton of coal transported. Other revenue. Other revenue consists primarily of rental payments and surface damage fees related to certain land the Partnership owns that is recognized as revenue straight-line over time as they are earned and property tax revenues, which are recognized on a gross basis as earned over time. Transportation and processing services revenue. The Partnership owns transportation and processing infrastructure that is leased to third parties and collects throughput fees for which it recognizes revenue over time based on the coal tons transported over the beltlines or processed through the facilities. Contract modifications Contract modifications that impact the overall economics of the lease's potential future cash flows are evaluated in accordance with ASC 606. A majority of our contract modifications pertain to our coal and aggregates royalty contracts and include, but are not limited to, extending the lease term, changes to royalty rates, floor prices or minimum payments, assignment of the contract or termination due to the exhaustion of merchantable and mineable reserves. In accordance with the contract modification guidance in paragraphs 606-10-25-12 and 25-13, 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. During the three months ended March 31, 2018 , there was no material impact to revenues recognized resulting from contract modifications occurring during the period. Contract Assets and Liabilities The following table details the Partnership's Coal Royalty and Other segment receivables from contracts with customers and contract liabilities: March 31, January 1, (In thousands) 2018 2018 Receivables Total accounts receivable, net (including affiliates) $ 32,225 $ 24,047 Prepaid expenses and other (1) 458 2,830 Contract liabilities Current portion of deferred revenue $ 1,554 $ 1,973 Deferred revenue 14,622 11,858 1) Prepaid expenses and other include notes receivable from contracts with customers. The following table shows the activity related to the Partnership's Coal Royalty and Other segment deferred revenue: (In thousands) Three Months Ended March 31, 2018 Balance at December 31, 2017 $ 100,605 Cumulative adjustment for change in accounting principle recognized in partners' capital (86,774 ) Balance at January 1, 2018 (current and non-current) $ 13,831 Production Leases - Revenue Impact Production lease minimum revenue (372 ) Recoupments recognized in Coal and aggregates royalty revenue (2,265 ) Minimum Leases - Revenue Impact Minimum lease amortization recognized in Minimum lease straight-line revenue (953 ) Cash received for minimum payments 5,935 Balance at March 31, 2018 (current and non-current) $ 16,176 Remaining Performance Obligations The Partnership's non-cancelable annual minimum payments due under terms of its coal and aggregates royalty leases by lease term are as follows: Weighted Average Remaining Years as of March 31, 2018 Annual Minimum Payments (In thousands) Lease Term (1) 1 - 5 years 0.3 $ 6,762 6 - 10 years 1.6 15,761 10+ years 8.9 41,009 Total 10.8 $ 63,532 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. 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. Soda Ash Segment NRP owns a non-controlling 49% interest in Ciner Wyoming LLC, ("Ciner Wyoming"), a trona ore mining operation that produces natural soda ash. NRP accounts for its investing in Ciner Wyoming using the equity method of accounting. The Partnership accounts for its investment in Ciner Wyoming using the equity method of accounting. Revenues and other income related to our equity investment in Ciner Wyoming were $9.6 million during the three months ended March 31, 2018 . Construction Aggregates Segment The following table represents the Partnership's Construction Aggregates segment revenues from contracts with customers by major source: (In thousands) Three Months Ended March 31, 2018 Crushed stone, sand and gravel $ 13,739 Delivery and fuel income 10,083 Other revenues 2,602 Total construction aggregates revenues $ 26,424 Road construction and asphalt paving services 728 Gain on asset sales, net 9 Total construction aggregates segment revenues and other income $ 27,161 The majority of the Construction Aggregates segment revenues is recognized at a point in time. Additional discussion of the Partnership's major sources of Construction Aggregates segment revenue are as follows: Crushed stone, sand and gravel and other. Revenue from the sale of crushed stone, sand, gravel and asphalt is recognized based on a fixed price when title is transferred to the buyer and collectibility of the sales proceeds is reasonably assured (typically occurs when products are picked up or delivered to the customer). Other revenues consist of brokered stone sales and barge and service revenues. Brokered stone sales include aggregates purchases from third party quarries, which are then sold and transported to customers and recorded as revenue at the time of delivery. The purchase price of the aggregates from the third party quarries are recorded as expenses. Barge and service revenues relate to loading and unloading services at marine terminals and are recorded as revenue at the time the service is performed. Delivery and fuel income. Revenue related to pass through transportation and fuel costs the Partnership incurs and pays for delivery of its products to customers. The related costs are recognized when incurred and are included in Operating and maintenance expenses on the Consolidated Statements of Comprehensive Income. Road construction and asphalt paving services revenue. Revenue related to construction contracts are recognized on the percentage-of-completion method, measured by the percentage of total costs incurred to date to the estimated total costs for each contract. The majority of the Partnership's construction contracts have an original expected duration of one year or less. As such, the Partnership has elected to apply the practical expedient for disclosing remaining performance obligations for contracts with an original expected duration of one year or less. The Partnership had $19.4 million and $23.0 million in receivables from Construction Aggregates segment related contracts with customers including in Accounts receivable, net on its Consolidated Balance Sheets at of March 31, 2018 and January 1, 2018, respectively.

Class A Convertible Preferred U

Class A Convertible Preferred Units and Warrants	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Convertible Preferred Units and Warrants	Class A Convertible Preferred Units 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"). 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 from December 31, 2017 to March 31, 2018 : (In thousands, except unit data) Units Outstanding Financial Position Balance at December 31, 2017 258,844 $ 173,431 Redemption of PIK units (8,844 ) (8,844 ) Balance at March 31, 2018 250,000 $ 164,587

Common and Preferred Unit Distr

Common and Preferred Unit Distributions	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Common and Preferred Unit Distributions	Common and Preferred Unit Distributions The Partnership makes cash distributions to common unitholders on a quarterly basis, subject to approval by the Board of Directors. The Partnership also makes distributions to the preferred unitholders 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"), subject to approval by the Board of Directors. 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 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 three months ended March 31, 2018 and 2017 : 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 2017 February 14, 2017 October 1 - December 31, 2016 $ 0.45 $ 5,503 $ 112 $ 5,615 Preferred Unit Distributions The following table shows the distributions declared and paid to Preferred Unitholders during the three months ended March 31, 2018 : Date Paid Period Covered by Distribution Distribution per Preferred Unit Cash Distributions Total Distribution Declared February 7, 2018 October 1 - December 31, 2017 $ 30.00 $ 7,765 $ 7,765 Income available to common unitholders and the general partner is reduced by Preferred Unit distributions that accumulated during the period. During the three months ended March 31, 2018 , NRP reduced net income attributable to common unitholders and the general partner by $7.5 million as a result of accumulated Preferred Unit distributions to be paid during the three months ended June 30, 2018.

Net Income Per Common Unit

Net Income Per Common Unit	3 Months Ended
	Mar. 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 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. Interest recognized during the period (including the effect of accretion of discounts and amortization of issuance costs, if any) and 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 three months ended March 31, 2018 and 2017 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: Three Months Ended (In thousands, except per unit data) 2018 2017 Allocation of net income: Net income from continuing operations $ 26,088 $ 6,111 Less: income attributable to preferred unitholders 7,500 2,500 Less: net income from continuing operations and income attributable to preferred unitholders allocated to the general partner 371 4 Net income from continuing operations attributable to common unitholders $ 18,217 $ 3,607 Net loss from discontinued operations $ (14 ) $ (207 ) Less: net loss from discontinued operations attributable to the general partner — (4 ) Net loss from discontinued operations attributable to common unitholders $ (14 ) $ (203 ) Net income $ 26,074 $ 5,904 Less: income attributable to preferred unitholders 7,500 2,500 Less: net income and income attributable to preferred unitholders allocated to the general partner 371 — Net income attributable to common unitholders $ 18,203 $ 3,404 Basic income (loss) per common unit: Weighted average common units—basic 12,238 12,232 Basic net income from continuing operations per common unit $ 1.49 $ 0.30 Basic net loss from discontinued operations per common unit — (0.02 ) Basic net income per common unit $ 1.49 $ 0.28 Diluted income (loss) per common unit: Weighted average common units—basic 12,238 12,232 Plus: dilutive effect of Warrants 424 322 Plus: dilutive effect of Preferred Units 9,463 2,391 Weighted average common units—diluted 22,125 14,945 Net income from continuing operations $ 26,088 $ 6,111 Less: net income from continuing operations allocated to the general partner 521 53 Diluted net income from continuing operations attributable to common unitholders $ 25,567 $ 6,058 Diluted net loss from discontinued operations attributable to common unitholders $ (14 ) $ (203 ) Net income $ 26,074 $ 5,904 Less: net income allocated to the general partner 521 49 Diluted net income attributable to common unitholders $ 25,553 $ 5,855 Diluted net income from continuing operations per common unit $ 1.16 $ 0.30 Diluted net loss from discontinued operations per common unit — (0.02 ) Diluted net income per common unit $ 1.15 $ 0.28

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information The Partnership's operating segments are strategic business units that offer distinct products and services to different customers in different geographies within the U.S. that are managed accordingly. NRP has the following three operating segments: Coal Royalty and Other —consists primarily of coal royalty and coal-related transportation and processing assets. Other assets include aggregates royalty, industrial mineral royalty, oil and gas royalty and timber. The Partnership's coal reserves are primarily located in Appalachia, the Illinois Basin and the Western 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 and Pennsylvania. Soda Ash —consists of the Partnership's 49% non-controlling equity interest in a trona ore mining operation and soda ash refinery in the Green River Basin, 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. The Partnership receives regular quarterly distributions from this business. Construction Aggregates —consists of the Partnership's construction aggregates materials business that operates hard rock quarries, an underground limestone mine, sand and gravel plants, asphalt plants and marine terminals. Construction Aggregates operates in Pennsylvania, West Virginia, Tennessee, Kentucky and Louisiana. 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: 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. Intersegment sales are at prices that approximate market. 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 operating segments: Operating Segments (In thousands) Coal Royalty and Other Soda Ash Construction Aggregates Corporate and Financing Total Three Months Ended March 31, 2018 Revenues (including affiliates) $ 51,593 $ 9,621 $ 27,152 $ — $ 88,366 Intersegment revenues (expenses) 41 — (41 ) — — Gain on asset sales, net 651 — 9 — 660 Operating and maintenance expenses 6,215 — 26,218 — 32,433 General and administrative (including affiliates) — — — 4,336 4,336 Depreciation, depletion and amortization 5,100 — 2,857 — 7,957 Asset impairment 242 — — — 242 Other expense, net — — 20 17,950 17,970 Net income (loss) from continuing operations 40,728 9,621 (1,975 ) (22,286 ) 26,088 Loss from discontinued operations — — — — (14 ) Three Months Ended March 31, 2017 Revenues (including affiliates) $ 51,138 $ 10,294 $ 27,221 $ — $ 88,653 Intersegment revenues (expenses) 62 — (62 ) — — Gain on asset sales, net 29 — 15 — 44 Operating and maintenance expenses 7,384 — 24,799 — 32,183 General and administrative (including affiliates) — — — 7,202 7,202 Depreciation, depletion and amortization (including affiliates) 6,973 — 3,519 — 10,492 Asset impairment 1,778 — — — 1,778 Other expense, net — — 395 30,536 30,931 Net income (loss) from continuing operations 35,094 10,294 (1,539 ) (37,738 ) 6,111 Loss from discontinued operations — — — — (207 ) As of March 31, 2018 Total assets of continuing operations $ 943,334 $ 241,679 $ 186,346 $ 4,856 $ 1,376,215 Total assets of discontinued operations — — — — 991 As of December 31, 2017 Total assets of continuing operations $ 945,237 $ 245,433 $ 191,374 $ 6,129 $ 1,388,173 Total assets of discontinued operations — — — — 991

Equity Investment

Equity Investment	3 Months Ended
	Mar. 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: Three Months Ended (In thousands) 2018 2017 Balance at beginning of period $ 245,433 $ 255,901 Income allocation to NRP’s equity interests 10,832 11,480 Amortization of basis difference (1,211 ) (1,186 ) Comprehensive loss from unconsolidated investment (1,125 ) (1,142 ) Distribution (12,250 ) (12,250 ) Balance at end of period $ 241,679 $ 252,803 The following table represents summarized financial information for Ciner Wyoming as derived from the respective unaudited financial statements for the three months ended March 31, 2018 and 2017, respectively: Three Months Ended (In thousands) 2018 2017 Sales $ 121,219 $ 126,572 Gross profit 28,222 28,697 Net Income 22,107 23,428

Plant and Equipment

Plant and Equipment	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Plant and Equipment	Plant and Equipment The Partnership’s plant and equipment consist of the following: March 31, December 31, (In thousands) 2018 2017 Plant and equipment $ 87,197 $ 84,173 Construction in process 1,169 803 Less accumulated depreciation (41,129 ) (38,806 ) Total plant and equipment, net $ 47,237 $ 46,170 Depreciation expense related to the Partnership's plant and equipment totaled $2.4 million and $3.0 million for the three months ended March 31, 2018 and 2017 , respectively, and is included in Depreciation, depletion and amortization on the Partnership's Consolidated Statements of Comprehensive Income.

Mineral Rights

Mineral Rights	3 Months Ended
	Mar. 31, 2018
Extractive Industries [Abstract]
Mineral Rights	Mineral Rights The Partnership’s mineral rights consist of the following: March 31, 2018 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,169,861 $ (440,599 ) $ 729,262 Aggregates properties 150,642 (17,754 ) 132,888 Oil and gas royalty properties 12,395 (7,375 ) 5,020 Other 13,163 (1,488 ) 11,675 Total $ 1,346,061 $ (467,216 ) $ 878,845 December 31, 2017 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,170,104 $ (436,964 ) $ 733,140 Aggregates properties 150,642 (16,836 ) 133,806 Oil and gas royalty properties 12,395 (7,158 ) 5,237 Other 13,168 (1,466 ) 11,702 Total $ 1,346,309 $ (462,424 ) $ 883,885 Depletion expense related to the Partnership’s mineral rights totaled $4.8 million and $6.6 million for the three months ended March 31, 2018 and 2017 , respectively, and is included in Depreciation, depletion and amortization on the Partnership's Consolidated Statements of Comprehensive Income. In April 2018, Foresight Energy LP ("Foresight Energy") made a filing with the SEC indicating its intent to permanently close the Deer Run mine operated by its subsidiary Hillsboro Energy LLC ("Hillsboro") if the coal mining lease is terminated by the Court in connection with the ongoing litigation relating thereto. Refer to Note 15. Commitments and Contingencies —Legal —Foresight Energy Disputes for more information on this litigation. In addition, Foresight Energy stated its intent to impair certain long-lived assets in the second quarter of 2018, including mineral reserves, buildings and structures, machinery and equipment, and other related assets that are not expected to generate future positive cash flows at the Deer Run mine. The Partnership has evaluated the impact of this announcement by Foresight Energy on its estimate of future cash flows from its Hillsboro property. To the extent the Partnership is unable to generate sufficient cash flow, the carrying value of the Partnership's reserves could be impaired. However, NRP believes there is no basis for termination of the lease, and the lease will remain in full force and effect unless the Court allows Hillsboro to bring its counterclaim and ultimately declares the lease terminated. Further, NRP believes that the approximately 179 million tons of estimated coal reserves at the Deer Run mine have substantial economic value. As a result, the Partnership has concluded there is no impairment of the $235 million net book value as of March 31, 2018 of the Partnership's reserves at the Deer Run mine. NRP will continue to assess the expected cash flow from this property in future periods.

Intangible Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets (Including Affiliate)	Intangible Assets The Partnership's intangible assets primarily consist of above-market coal 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 also include permits, aggregates-related trade names and other agreements. The Partnership's intangible assets included on its Consolidated Balance Sheets are as follows: March 31, December 31, (In thousands) 2018 2017 Intangible assets $ 86,336 $ 86,336 Less: accumulated amortization (37,567 ) (36,782 ) Total intangible assets, net $ 48,769 $ 49,554 As of May 9, 2017, Foresight Energy is no longer deemed to be an affiliate of the Partnership. Refer to Note 13. Related Party Transactions for additional details. Amortization expense included in Depreciation, depletion and amortization on the Consolidated Statements of Comprehensive Income was $0.8 million and $0.2 million for the three months ended March 31, 2018 and 2017 , respectively. Amortization expense included in amortization expense—affiliates on the Partnership's Consolidated Statements of Comprehensive Income was $0.8 million for the three months ended March 31, 2017 .

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt The Partnership's debt consists of the following: March 31, 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 95,000 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 4,586 8.38% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2019 21,334 42,670 5.05% with semi-annual interest payments in January and July, with annual principal payments in July, due July 2020 22,946 22,946 5.55% with semi-annual interest payments in June and December, with annual principal payments in June, due June 2023 16,115 16,115 4.73% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2023 44,693 44,693 5.82% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 89,589 104,520 8.92% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 27,200 31,733 5.03% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 120,547 120,547 5.18% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 34,396 34,396 Total debt at face value $ 822,044 $ 827,844 Net unamortized debt discount (1,562 ) (1,661 ) Net unamortized debt issuance costs (15,905 ) (16,835 ) Total debt, net $ 804,577 $ 809,348 Less: current portion of long-term debt 79,723 79,740 Total long-term debt, net $ 724,854 $ 729,608 NRP LP Debt 2022 Senior Notes As of March 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 March 31, 2018 and December 31, 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 March 31, 2018 , Opco had $95.0 million of indebtedness outstanding and $55.0 million in available borrowing capacity under the Opco Credit Facility. The commitments under the Opco Credit Facility will be reduced from $150 million to $100 million at December 31, 2018 and remaining at $100 million through maturity in April 2020. The weighted average interest rates for the borrowings outstanding under the Opco Credit Facility for three months ended March 31, 2018 and 2017 were 5.91% and 5.22% , respectively. Debt issue cost related to the Opco credit facility were $3.9 million and $4.6 million at March 31, 2018 and December 31, 2017 , respectively, and have been capitalized and included in Other assets on the Partnership's Consolidated Balance Sheets. The Opco Credit Facility is collateralized and secured by liens on certain of Opco’s assets with carrying values of $646.3 million and $649.7 million classified as Land, Plant and equipment and Mineral rights on the Partnership’s Consolidated Balance Sheet as of March 31, 2018 and December 31, 2017 , respectively. Opco Senior Notes As of March 31, 2018 and December 31, 2017 , the private placement senior notes ("Opco Senior Notes") had cumulative principal balances of $381.4 million and $422.2 million , respectively. Opco made mandatory principal payments of $40.8 million during both the three months ended March 31, 2018 and 2017 . 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 March 31, 2018 .

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value of Financial Instruments The Partnership’s financial instruments consist of cash and cash equivalents, accounts receivable, contracts receivable, accounts payable, debt, Preferred Units and warrants. The carrying amounts reported on the Consolidated Balance Sheets for cash and cash equivalents, accounts receivable and accounts payable 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 three months ended March 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: March 31, 2018 December 31, 2017 (In thousands) Carrying Estimated Carrying Estimated Debt: NRP 2022 Senior Notes (1) $ 331,309 $ 371,561 $ 330,404 $ 366,376 Opco Senior Notes (2) 378,268 410,011 418,944 447,538 Opco Revolving Credit Facility (3) 95,000 95,000 60,000 60,000 Assets: Contracts receivable, current and long-term (4) $ 43,312 $ 30,332 $ 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 income (expense) in the Partnership's Consolidated Statements of Comprehensive Income. The embedded derivatives had zero value as of March 31, 2018 and December 31, 2017 .

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Cline Affiliates and Foresight Energy L.P. 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 LP ("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. 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 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 the Partnership's Consolidated Statements of Comprehensive Income as follows: Three Months Ended (In thousands) 2018 2017 Coal royalty and other revenue $ 7,048 $ — Coal royalty and other—affiliates revenue — 11,152 Transportation and Processing Services Revenues and Expenses The Partnership owns transportation and processing infrastructure related to certain of our coal properties, including loadout and other transportation assets at Foresight Energy's Williamson and Macoupin mines in the Illinois Basin. 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 do not own coal reserves at the Sugar Camp mine. This infrastructure is leased to third parties and NRP collects throughput fees, which are included in the Partnership's Consolidated Statements of Comprehensive Income as follows: Three Months Ended (In thousands) 2018 2017 Transportation and processing services $ 5,383 $ — Transportation and processing services—affiliate — 4,639 NRP is responsible for operating and maintaining the rail load out transportation assets at the Williamson mine and subcontracts the operating responsibilities to a subsidiary of Foresight Energy. Expenses related to these transactions with Foresight Energy are included in the Partnership's Consolidated Statements of Comprehensive Income as follows: Three Months Ended (In thousands) 2018 2017 Operating and maintenance expense $ 401 $ — Operating and maintenance expense—affiliates — 335 Total $ 401 $ 335 NRP's Sugar Camp rail load out lease with a subsidiary of Foresight Energy is accounted for as a direct financing lease. The following table shows certain amounts related to NRP's Sugar Camp rail load out facility direct financing lease: March 31, December 31, (In thousands) 2018 2017 Projected remaining payments $ 70,225 $ 71,452 Unearned income 27,526 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. The Partnership had Accounts payable—affiliates on its Consolidated Balance Sheets to QMC of $1.1 million and WPPLP of $1.0 million as of March 31, 2018 and to QMC of $0.4 million and WPPLP of $0.1 million as of December 31, 2017 . 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: Three Months Ended (In thousands) 2018 2017 Operating and maintenance expenses—affiliates $ 1,907 $ 2,135 General and administrative—affiliates 931 1,124 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 March 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. Corbin J. Robertson III, one of the Partnership’s directors, was Chairman of the Board of Corsa through May 10, 2017. Coal related revenues from Corsa totaled $0.2 million and $0.4 million for the three months ended March 31, 2018 and 2017 , respectively. At March 31, 2018 and December 31, 2017 , the Partnership had Accounts receivable—affiliates totaling $0.1 million and $0.2 million from Corsa on its Consolidated Balance Sheets, respectively. WPPLP Production Royalty and Overriding Royalty During the three months ended March 31, 2018 and 2017 , the Partnership recorded $0.6 million and $0.1 million in Operating and maintenance expenses—affiliates, respectively, on its Statements of Comprehensive Income related to a non-participating production royalty payable to WPPLP pursuant to a conveyance agreement entered into in 2007. The Partnership had Other assets—affiliate from WPPLP of $0.2 million at December 31, 2017 on its Consolidated Balance Sheets related to a non-production royalty receivable from WPPLP for overriding royalty interest on a mine.

Major Customers

Major Customers	3 Months Ended
	Mar. 31, 2018
Risks and Uncertainties [Abstract]
Major Customers	Major Customers Revenues from customers that exceeded 10 percent of total revenues and other income for any of the periods presented below are as follows: Three Months Ended March 31, 2018 2017 (In thousands) Revenues Percent Revenues Percent Foresight Energy $ 12,431 14.0 % $ 15,791 17.8 % Revenues from Foresight Energy are included within the Partnership's Coal Royalty and Other segment.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 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. NRP is also currently involved in the legal proceedings 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 alleging 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 intends to vigorously defend this lawsuit. However, the ultimate outcome cannot be predicted with certainty given the early stage of this matter, 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 Disputes In November 2015, NRP filed a lawsuit against Hillsboro and has subsequently named Foresight Energy and certain of its other subsidiaries in that lawsuit. The lawsuit alleges, among other items, breach of contract by Hillsboro resulting from a wrongful declaration of force majeure at Hillsboro’s Deer Run mine, as well as alter-ego and tortious interference claims against Foresight Energy. In late March 2015, elevated carbon monoxide readings were detected at the Deer Run mine, and coal production at the mine was idled. In July 2015, Hillsboro declared a force majeure event under its lease with us, and Hillsboro has failed to make its contractually obligated minimum quarterly payments of $7.5 million since then. NRP believes the force majeure declaration by Hillsboro has no merit and is vigorously pursuing recovery against Hillsboro as well as against Foresight Energy and certain of its other subsidiaries. In April 2018, Hillsboro filed a motion with the Court asking to be allowed to file a counterclaim seeking a declaration that the lease terminated retroactively effective March 26, 2015. We believe there is no basis for termination of the lease, and the lease will remain in full force and effect unless the Court allows Hillsboro to bring its counterclaim and ultimately declares the lease terminated. Hillsboro has failed to make $83.5 million of required quarterly minimum payments to NRP to date, and such amount will continue to increase by $7.5 million for each quarter with respect to which payment is not made. Additionally, approximately $12.8 million of interest on the unpaid amounts has accrued to date. In April 2016, NRP filed a lawsuit against Macoupin Energy, LLC ("Macoupin"), a subsidiary of Foresight Energy, in Macoupin County, Illinois. The lawsuit alleges that Macoupin has failed to comply with the terms of its coal mining, rail loadout and rail loop leases by incorrectly recouping previously paid minimum royalties. As a result, Macoupin owes NRP approximately $9.5 million in improperly recouped minimum royalties through March 31, 2018 .

Unit-Based Compensation (Notes)

Unit-Based Compensation (Notes)	3 Months Ended
	Mar. 31, 2018
Unit-Based Compensation [Abstract]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	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 will determine the terms and conditions of awards granted under the 2017 LTIP. The Partnership recognizes 2017 LTIP forfeitures 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 three 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 distribution equivalent rights until issuance. A summary of the activity during three months ended March 31, 2018 is as follows: (In thousands) Common Units Weighted Average Exercise Price Outstanding at January 1, 2018 — $ — Granted 75 $ 29.16 Fully vested and issued (14 ) $ 29.44 Forfeitures — $ — Outstanding at March 31, 2018 61 $ 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 were issued. Unit-based compensation expense associated with these awards was $0.6 million for the three months ended March 31, 2018 and is included in General and administrative expense and Operating and maintenance expense in the Partnership's Consolidated Statements of Comprehensive Income. The unamortized cost associated with unvested outstanding grants as of March 31, 2018 is $1.6 million recognized over a weighted-average period of 2.9 years .

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The following represents material events that have occurred subsequent to March 31, 2018 through the time of the Partnership’s filing of its Quarterly Report on Form 10-Q with the SEC: Distributions Declared On April 25, 2018, the Board of Directors of GP Natural Resource Partners LLC declared a distribution of $0.45 per common unit to be paid by the Partnership on May 14, 2018 to common unitholders of record on May 7, 2018. In addition, the Board declared a distribution on NRP's 12.0% Class A Convertible Preferred Units with respect to the first quarter totaling $7.5 million in cash.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Principles of Consolidation Reporting	Principles of Consolidation and Reporting The accompanying unaudited Consolidated Financial Statements of the Partnership have been prepared in accordance with generally accepted accounting principles in the United States of America ("GAAP") for interim financial information and with Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In management's opinion, all necessary adjustments to fairly present the Partnership's results of operations, financial position and cash flows for the periods presented have been made and all such adjustments were of a normal and recurring nature. Certain reclassifications have been made to prior period amounts on the Statements of Comprehensive Income and Statements of Cash Flows to conform with current period presentation. These reclassifications had no impact on previously reported net income or cash flows from operating, investing or financing activities.
Recently Issued Accounting Standards	Recently Adopted Accounting Standards Revenue Recognition. On January 1, 2018, NRP adopted accounting standard 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 the cumulative effect of adoption as an adjustment to 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 Construction Aggregates or Soda Ash operating segments. 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 amount, opposed to when the recoupment period for that minimum payment expired under the previous guidance. The cumulative effects of the changes made to our 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 $ 47,026 $ 3,479 $ 50,505 Liabilities Current portion of deferred revenue $ — $ 1,973 $ 1,973 Deferred revenue 100,605 (88,747 ) 11,858 Partners’ capital Common unitholders’ interest $ 199,851 $ 88,448 $ 288,299 General partner’s interest 1,857 1,805 3,662 Total partners’ capital 265,211 90,253 355,464 The impact of adoption of the new revenue standard on NRP’s Consolidated Statement of Comprehensive Income and Consolidated Balance Sheet was as follows: For the Three Months ended March 31, 2018 (In thousands) As Reported Amounts without Adoption of ASC 606 Effect of Change Coal royalty and other revenues $ 45,973 $ 47,671 $ (1,698 ) Net income from continuing operations 26,088 27,786 (1,698 ) Net income 26,074 27,772 (1,698 ) Net income per common unit (basic) 1.49 1.63 (0.14 ) Net income per common unit (diluted) 1.15 1.23 (0.08 ) As of March 31, 2018 (In thousands) As Reported Balances without Adoption of ASC 606 Effect of Change Assets Accounts receivable, net $ 55,651 $ 48,556 $ 7,095 Total assets 1,377,206 1,370,111 7,095 Liabilities and capital Current portion of deferred revenue $ 1,554 $ — $ 1,554 Deferred revenue 14,622 97,636 (83,014 ) Total liabilities 848,367 929,827 (81,460 ) Common unitholders’ interest 301,344 214,560 86,784 General partner’s interest 3,924 2,153 1,771 Total partners’ capital 367,646 279,091 88,555 Total liabilities and capital 1,377,206 1,370,111 7,095 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 31, 2018. The Partnership is currently evaluating the impact of the provisions of this guidance on its consolidated financial statements.

Basis of Presentation Basis of

Basis of Presentation Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Schedule of Effect of Adoption of New Accounting Policy	The cumulative effects of the changes made to our 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 $ 47,026 $ 3,479 $ 50,505 Liabilities Current portion of deferred revenue $ — $ 1,973 $ 1,973 Deferred revenue 100,605 (88,747 ) 11,858 Partners’ capital Common unitholders’ interest $ 199,851 $ 88,448 $ 288,299 General partner’s interest 1,857 1,805 3,662 Total partners’ capital 265,211 90,253 355,464 The impact of adoption of the new revenue standard on NRP’s Consolidated Statement of Comprehensive Income and Consolidated Balance Sheet was as follows: For the Three Months ended March 31, 2018 (In thousands) As Reported Amounts without Adoption of ASC 606 Effect of Change Coal royalty and other revenues $ 45,973 $ 47,671 $ (1,698 ) Net income from continuing operations 26,088 27,786 (1,698 ) Net income 26,074 27,772 (1,698 ) Net income per common unit (basic) 1.49 1.63 (0.14 ) Net income per common unit (diluted) 1.15 1.23 (0.08 ) As of March 31, 2018 (In thousands) As Reported Balances without Adoption of ASC 606 Effect of Change Assets Accounts receivable, net $ 55,651 $ 48,556 $ 7,095 Total assets 1,377,206 1,370,111 7,095 Liabilities and capital Current portion of deferred revenue $ 1,554 $ — $ 1,554 Deferred revenue 14,622 97,636 (83,014 ) Total liabilities 848,367 929,827 (81,460 ) Common unitholders’ interest 301,344 214,560 86,784 General partner’s interest 3,924 2,153 1,771 Total partners’ capital 367,646 279,091 88,555 Total liabilities and capital 1,377,206 1,370,111 7,095

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers by Source	The following table represents the Partnership's Coal Royalty and Other segment revenues (including affiliates) from contracts with customers by major source: Three Months Ended March 31, 2018 (In thousands) Coal royalty revenue $ 28,691 Production lease minimum revenue 425 Minimum lease straight-line revenue 6,760 Wheelage revenue 1,974 Coal overriding royalty revenue 2,872 Aggregates royalty revenue 1,091 Oil and gas royalty revenue 2,898 Property tax revenue 1,182 Other revenue 317 Coal royalty and other revenues (including affiliates) $ 46,210 Transportation and processing services revenue (1) 2,989 Gain on asset sales, net 651 Total coal royalty and other revenues and other income (including affiliates) from contracts with customers $ 49,850 (1) Total transportation and processing services revenue on the Partnership's Consolidated Statement of Comprehensive Income was $5.4 million for the three months ended March 31, 2018 . The $3.0 million represented above relates to contracts with customers where NRP is responsible for operating and maintaining certain rail load out transportation assets. The remaining $2.4 million revenue relates to other NRP-owned infrastructure leased to and operated by third party operators accounted for under ASC 840, Leases. The following table represents the Partnership's Construction Aggregates segment revenues from contracts with customers by major source: (In thousands) Three Months Ended March 31, 2018 Crushed stone, sand and gravel $ 13,739 Delivery and fuel income 10,083 Other revenues 2,602 Total construction aggregates revenues $ 26,424 Road construction and asphalt paving services 728 Gain on asset sales, net 9 Total construction aggregates segment revenues and other income $ 27,161
Schedule of Receivables and Liabilities from Contracts with Customers	The following table details the Partnership's Coal Royalty and Other segment receivables from contracts with customers and contract liabilities: March 31, January 1, (In thousands) 2018 2018 Receivables Total accounts receivable, net (including affiliates) $ 32,225 $ 24,047 Prepaid expenses and other (1) 458 2,830 Contract liabilities Current portion of deferred revenue $ 1,554 $ 1,973 Deferred revenue 14,622 11,858 1) Prepaid expenses and other include notes receivable from contracts with customers.
Activity Related to Partners' Coal Royalty and Other Segment Deferred Revenue	The following table shows the activity related to the Partnership's Coal Royalty and Other segment deferred revenue: (In thousands) Three Months Ended March 31, 2018 Balance at December 31, 2017 $ 100,605 Cumulative adjustment for change in accounting principle recognized in partners' capital (86,774 ) Balance at January 1, 2018 (current and non-current) $ 13,831 Production Leases - Revenue Impact Production lease minimum revenue (372 ) Recoupments recognized in Coal and aggregates royalty revenue (2,265 ) Minimum Leases - Revenue Impact Minimum lease amortization recognized in Minimum lease straight-line revenue (953 ) Cash received for minimum payments 5,935 Balance at March 31, 2018 (current and non-current) $ 16,176
Schedule of Annual Minimums by Current Remaining Contract Term	The Partnership's non-cancelable annual minimum payments due under terms of its coal and aggregates royalty leases by lease term are as follows: Weighted Average Remaining Years as of March 31, 2018 Annual Minimum Payments (In thousands) Lease Term (1) 1 - 5 years 0.3 $ 6,762 6 - 10 years 1.6 15,761 10+ years 8.9 41,009 Total 10.8 $ 63,532 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.

Class A Convertible Preferred27

Class A Convertible Preferred Units Temporary equity (Tables) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Temporary Equity Disclosure [Abstract]
Temporary Equity [Table Text Block]	Activity related to the Preferred Units is as follows from December 31, 2017 to March 31, 2018 : (In thousands, except unit data) Units Outstanding Financial Position Balance at December 31, 2017 258,844 $ 173,431 Redemption of PIK units (8,844 ) (8,844 ) Balance at March 31, 2018 250,000 $ 164,587
Temporary Equity [Line Items]
Income attributable to preferred unitholders	$ 7,500	$ 2,500
Increase (Decrease) in Temporary Equity [Roll Forward]
Beginning balance	173,431
Ending balance	$ 164,587

Common and Preferred Unit Dis28

Common and Preferred Unit Distributions (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Distributions Paid	The following table shows the distributions declared and paid to common unitholders during the three months ended March 31, 2018 and 2017 : 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 2017 February 14, 2017 October 1 - December 31, 2016 $ 0.45 $ 5,503 $ 112 $ 5,615 Preferred Unit Distributions The following table shows the distributions declared and paid to Preferred Unitholders during the three months ended March 31, 2018 : Date Paid Period Covered by Distribution Distribution per Preferred Unit Cash Distributions Total Distribution Declared February 7, 2018 October 1 - December 31, 2017 $ 30.00 $ 7,765 $ 7,765

Net Income Per Common Unit (Tab

Net Income Per Common Unit (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Reconciliation of Net Income to Weighted Average Units Outstanding	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: Three Months Ended (In thousands, except per unit data) 2018 2017 Allocation of net income: Net income from continuing operations $ 26,088 $ 6,111 Less: income attributable to preferred unitholders 7,500 2,500 Less: net income from continuing operations and income attributable to preferred unitholders allocated to the general partner 371 4 Net income from continuing operations attributable to common unitholders $ 18,217 $ 3,607 Net loss from discontinued operations $ (14 ) $ (207 ) Less: net loss from discontinued operations attributable to the general partner — (4 ) Net loss from discontinued operations attributable to common unitholders $ (14 ) $ (203 ) Net income $ 26,074 $ 5,904 Less: income attributable to preferred unitholders 7,500 2,500 Less: net income and income attributable to preferred unitholders allocated to the general partner 371 — Net income attributable to common unitholders $ 18,203 $ 3,404 Basic income (loss) per common unit: Weighted average common units—basic 12,238 12,232 Basic net income from continuing operations per common unit $ 1.49 $ 0.30 Basic net loss from discontinued operations per common unit — (0.02 ) Basic net income per common unit $ 1.49 $ 0.28 Diluted income (loss) per common unit: Weighted average common units—basic 12,238 12,232 Plus: dilutive effect of Warrants 424 322 Plus: dilutive effect of Preferred Units 9,463 2,391 Weighted average common units—diluted 22,125 14,945 Net income from continuing operations $ 26,088 $ 6,111 Less: net income from continuing operations allocated to the general partner 521 53 Diluted net income from continuing operations attributable to common unitholders $ 25,567 $ 6,058 Diluted net loss from discontinued operations attributable to common unitholders $ (14 ) $ (203 ) Net income $ 26,074 $ 5,904 Less: net income allocated to the general partner 521 49 Diluted net income attributable to common unitholders $ 25,553 $ 5,855 Diluted net income from continuing operations per common unit $ 1.16 $ 0.30 Diluted net loss from discontinued operations per common unit — (0.02 ) Diluted net income per common unit $ 1.15 $ 0.28

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 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 operating segments: Operating Segments (In thousands) Coal Royalty and Other Soda Ash Construction Aggregates Corporate and Financing Total Three Months Ended March 31, 2018 Revenues (including affiliates) $ 51,593 $ 9,621 $ 27,152 $ — $ 88,366 Intersegment revenues (expenses) 41 — (41 ) — — Gain on asset sales, net 651 — 9 — 660 Operating and maintenance expenses 6,215 — 26,218 — 32,433 General and administrative (including affiliates) — — — 4,336 4,336 Depreciation, depletion and amortization 5,100 — 2,857 — 7,957 Asset impairment 242 — — — 242 Other expense, net — — 20 17,950 17,970 Net income (loss) from continuing operations 40,728 9,621 (1,975 ) (22,286 ) 26,088 Loss from discontinued operations — — — — (14 ) Three Months Ended March 31, 2017 Revenues (including affiliates) $ 51,138 $ 10,294 $ 27,221 $ — $ 88,653 Intersegment revenues (expenses) 62 — (62 ) — — Gain on asset sales, net 29 — 15 — 44 Operating and maintenance expenses 7,384 — 24,799 — 32,183 General and administrative (including affiliates) — — — 7,202 7,202 Depreciation, depletion and amortization (including affiliates) 6,973 — 3,519 — 10,492 Asset impairment 1,778 — — — 1,778 Other expense, net — — 395 30,536 30,931 Net income (loss) from continuing operations 35,094 10,294 (1,539 ) (37,738 ) 6,111 Loss from discontinued operations — — — — (207 ) As of March 31, 2018 Total assets of continuing operations $ 943,334 $ 241,679 $ 186,346 $ 4,856 $ 1,376,215 Total assets of discontinued operations — — — — 991 As of December 31, 2017 Total assets of continuing operations $ 945,237 $ 245,433 $ 191,374 $ 6,129 $ 1,388,173 Total assets of discontinued operations — — — — 991

Equity Investment (Tables)

Equity Investment (Tables)	3 Months Ended
	Mar. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Summarized Financial Information	Activity related to this investment is as follows: Three Months Ended (In thousands) 2018 2017 Balance at beginning of period $ 245,433 $ 255,901 Income allocation to NRP’s equity interests 10,832 11,480 Amortization of basis difference (1,211 ) (1,186 ) Comprehensive loss from unconsolidated investment (1,125 ) (1,142 ) Distribution (12,250 ) (12,250 ) Balance at end of period $ 241,679 $ 252,803 The following table represents summarized financial information for Ciner Wyoming as derived from the respective unaudited financial statements for the three months ended March 31, 2018 and 2017, respectively: Three Months Ended (In thousands) 2018 2017 Sales $ 121,219 $ 126,572 Gross profit 28,222 28,697 Net Income 22,107 23,428

Plant and Equipment (Tables)

Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Plant and Equipment	The Partnership’s plant and equipment consist of the following: March 31, December 31, (In thousands) 2018 2017 Plant and equipment $ 87,197 $ 84,173 Construction in process 1,169 803 Less accumulated depreciation (41,129 ) (38,806 ) Total plant and equipment, net $ 47,237 $ 46,170

Mineral Rights (Tables)

Mineral Rights (Tables)	3 Months Ended
	Mar. 31, 2018
Extractive Industries [Abstract]
Mineral Rights	The Partnership’s mineral rights consist of the following: March 31, 2018 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,169,861 $ (440,599 ) $ 729,262 Aggregates properties 150,642 (17,754 ) 132,888 Oil and gas royalty properties 12,395 (7,375 ) 5,020 Other 13,163 (1,488 ) 11,675 Total $ 1,346,061 $ (467,216 ) $ 878,845 December 31, 2017 (In thousands) Carrying Value Accumulated Depletion Net Book Value Coal properties $ 1,170,104 $ (436,964 ) $ 733,140 Aggregates properties 150,642 (16,836 ) 133,806 Oil and gas royalty properties 12,395 (7,158 ) 5,237 Other 13,168 (1,466 ) 11,702 Total $ 1,346,309 $ (462,424 ) $ 883,885

Intangible Assets (Tables)

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets [Table Text Block]	The Partnership's intangible assets included on its Consolidated Balance Sheets are as follows: March 31, December 31, (In thousands) 2018 2017 Intangible assets $ 86,336 $ 86,336 Less: accumulated amortization (37,567 ) (36,782 ) Total intangible assets, net $ 48,769 $ 49,554

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	The Partnership's debt consists of the following: March 31, 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 95,000 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 4,586 8.38% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2019 21,334 42,670 5.05% with semi-annual interest payments in January and July, with annual principal payments in July, due July 2020 22,946 22,946 5.55% with semi-annual interest payments in June and December, with annual principal payments in June, due June 2023 16,115 16,115 4.73% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2023 44,693 44,693 5.82% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 89,589 104,520 8.92% with semi-annual interest payments in March and September, with annual principal payments in March, due March 2024 27,200 31,733 5.03% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 120,547 120,547 5.18% with semi-annual interest payments in June and December, with annual principal payments in December, due December 2026 34,396 34,396 Total debt at face value $ 822,044 $ 827,844 Net unamortized debt discount (1,562 ) (1,661 ) Net unamortized debt issuance costs (15,905 ) (16,835 ) Total debt, net $ 804,577 $ 809,348 Less: current portion of long-term debt 79,723 79,740 Total long-term debt, net $ 724,854 $ 729,608

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 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: March 31, 2018 December 31, 2017 (In thousands) Carrying Estimated Carrying Estimated Debt: NRP 2022 Senior Notes (1) $ 331,309 $ 371,561 $ 330,404 $ 366,376 Opco Senior Notes (2) 378,268 410,011 418,944 447,538 Opco Revolving Credit Facility (3) 95,000 95,000 60,000 60,000 Assets: Contracts receivable, current and long-term (4) $ 43,312 $ 30,332 $ 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)	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Expenses related to these transactions with Foresight Energy are included in the Partnership's Consolidated Statements of Comprehensive Income as follows: Three Months Ended (In thousands) 2018 2017 Operating and maintenance expense $ 401 $ — Operating and maintenance expense—affiliates — 335 Total $ 401 $ 335 NRP's Sugar Camp rail load out lease with a subsidiary of Foresight Energy is accounted for as a direct financing lease. The following table shows certain amounts related to NRP's Sugar Camp rail load out facility direct financing lease: March 31, December 31, (In thousands) 2018 2017 Projected remaining payments $ 70,225 $ 71,452 Unearned income 27,526 28,366 Revenues related to these transactions are included in the Partnership's Consolidated Statements of Comprehensive Income as follows: Three Months Ended (In thousands) 2018 2017 Coal royalty and other revenue $ 7,048 $ — Coal royalty and other—affiliates revenue — 11,152 This infrastructure is leased to third parties and NRP collects throughput fees, which are included in the Partnership's Consolidated Statements of Comprehensive Income as follows: Three Months Ended (In thousands) 2018 2017 Transportation and processing services $ 5,383 $ — Transportation and processing services—affiliate — 4,639
Summary of Reimbursements	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: Three Months Ended (In thousands) 2018 2017 Operating and maintenance expenses—affiliates $ 1,907 $ 2,135 General and administrative—affiliates 931 1,124

Major Customers (Tables)

Major Customers (Tables)	3 Months Ended
	Mar. 31, 2018
Risks and Uncertainties [Abstract]
Major customers	Revenues from customers that exceeded 10 percent of total revenues and other income for any of the periods presented below are as follows: Three Months Ended March 31, 2018 2017 (In thousands) Revenues Percent Revenues Percent Foresight Energy $ 12,431 14.0 % $ 15,791 17.8 % Revenues from Foresight Energy are included within the Partnership's Coal Royalty and Other segment.

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Income	$ 26,074	[1]	$ 5,904
[1]	Net income includes $7.5 million attributable to Preferred Unitholders that accumulated during the period, of which $7.4 million is allocated to the common unitholders and $0.2 million is allocated to the general partner.

Basis of Presentation - Summary

Basis of Presentation - Summary of Effect of New Accounting Pronouncement on Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 55,651	$ 50,505	$ 47,026
Current portion of deferred revenue	1,554	1,973	0
Deferred revenue	14,622	11,858	100,605
Common unitholders’ interest	301,344	288,299	199,851
General partner’s interest	3,924	3,662	1,857
Cumulative effect of adoption of accounting standard (See Note 2)		90,253
Total partners’ capital	367,646	355,464	265,211
Amounts without Adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	48,556		47,026
Current portion of deferred revenue	0		0
Deferred revenue	97,636		100,605
Common unitholders’ interest	214,560		199,851
General partner’s interest	2,153		1,857
Total partners’ capital	279,091		$ 265,211
Accounting Standards Update 2014-09 | Effect of Change
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	7,095	3,479
Current portion of deferred revenue	1,554	1,973
Deferred revenue	(83,014)	(88,747)
Common unitholders’ interest	86,784	88,448
General partner’s interest	1,771	1,805
Total partners’ capital	$ 88,555	$ 90,253

Basis of Presentation - Summa41

Basis of Presentation - Summary of Effect of New Accounting Pronouncement on Statement of Comprehensive Income and Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
(In thousands)
Coal royalty and other revenues	$ 88,366		$ 88,653
Net income from continuing operations	26,088		6,111
Net income	$ 26,074	[1]	$ 5,904
Net income per common unit (basic)	$ 1.49		$ 0.28
Net income per common unit (diluted)	$ 1.15		$ 0.28
(In thousands)
Accounts receivable, net	$ 55,651			$ 50,505	$ 47,026
Total assets	1,377,206				1,389,164
Current portion of deferred revenue	1,554			1,973	0
Deferred revenue	14,622			11,858	100,605
Total liabilities	848,367				953,916
Common unitholders’ interest	301,344			288,299	199,851
General partner’s interest	3,924			3,662	1,857
Total partners’ capital	367,646			355,464	265,211
Total liabilities and capital	1,377,206				1,389,164
Amounts without Adoption of ASC 606
(In thousands)
Coal royalty and other revenues	47,671
Net income from continuing operations	27,786
Net income	$ 27,772
Net income per common unit (basic)	$ 1.63
Net income per common unit (diluted)	$ 1.23
(In thousands)
Accounts receivable, net	$ 48,556				47,026
Total assets	1,370,111
Current portion of deferred revenue	0				0
Deferred revenue	97,636				100,605
Total liabilities	929,827
Common unitholders’ interest	214,560				199,851
General partner’s interest	2,153				1,857
Total partners’ capital	279,091				$ 265,211
Total liabilities and capital	1,370,111
Accounting Standards Update 2014-09 | Effect of Change
(In thousands)
Coal royalty and other revenues	(1,698)
Net income from continuing operations	(1,698)
Net income	$ (1,698)
Net income per common unit (basic)	$ (0.14)
Net income per common unit (diluted)	$ (0.08)
(In thousands)
Accounts receivable, net	$ 7,095			3,479
Total assets	7,095
Current portion of deferred revenue	1,554			1,973
Deferred revenue	(83,014)			(88,747)
Total liabilities	(81,460)
Common unitholders’ interest	86,784			88,448
General partner’s interest	1,771			1,805
Total partners’ capital	88,555			$ 90,253
Total liabilities and capital	$ 7,095
[1]	Net income includes $7.5 million attributable to Preferred Unitholders that accumulated during the period, of which $7.4 million is allocated to the common unitholders and $0.2 million is allocated to the general partner.

Revenue Recognition - Schedule

Revenue Recognition - Schedule of Partnerships' Coal Royalty and Other Segment Revenues from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	$ 49,850
Revenue, Net	88,366	$ 88,653
Transportation and processing services revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	2,989
Gain on asset sales, net
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	651
Coal Royalty and Other
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	46,210
Revenue, Net	45,973	34,994
Coal Royalty and Other | Coal royalty revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	28,691
Coal Royalty and Other | Production lease minimum revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	425
Coal Royalty and Other | Minimum lease straight-line revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	6,760
Coal Royalty and Other | Wheelage revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	1,974
Coal Royalty and Other | Coal overriding royalty revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	2,872
Coal Royalty and Other | Aggregates royalty revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	1,091
Coal Royalty and Other | Oil and gas royalty revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	2,898
Coal Royalty and Other | Property tax revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	1,182
Coal Royalty and Other | Other revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	317
Coal Royalty and Other | Transportation and Processing
Disaggregation of Revenue [Line Items]
Revenue, Net	5,383	$ 0
Lease revenue	$ 2,400

Revenue Recognition - Narrative

Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jul. 31, 2013	Jan. 31, 2013
Minimum
Disaggregation of Revenue [Line Items]
Lease term	5 years
Recoupable period	3 years
Maximum
Disaggregation of Revenue [Line Items]
Lease term	40 years
Recoupable period	5 years
Operating Segments | Construction Aggregates
Disaggregation of Revenue [Line Items]
Trade Accounts Receivable	$ 19.4	$ 23
Ciner Wyoming
Disaggregation of Revenue [Line Items]
Noncontrolling interest (percent)	49.00%		49.00%	48.51%
Royalty Leases
Disaggregation of Revenue [Line Items]
Minimum lease payments due 2023	$ 1.8
Minimum lease payments expiring upon exhaustion	$ 1

Revenue Recognition - Schedul44

Revenue Recognition - Schedule of Receivables and Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Total accounts receivable, net (including affiliates)	$ 32,225	$ 24,047
Prepaid expenses and other	458,000		$ 2,830
Current portion of deferred revenue	1,554	1,973	0
Deferred revenue	$ 14,622	$ 11,858	$ 100,605

Revenue Recognition - Activity

Revenue Recognition - Activity Related to Partners' Coal Royalty and Other Segment Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018
Disaggregation of Revenue [Line Items]
Balance beginning of period	$ 100,605
Deferred revenue	100,605	$ 13,831
Production lease minimum revenue	(372)
Recoupments recognized in Coal and aggregates royalty revenue	(2,265)
Minimum lease amortization recognized in Minimum lease straight-line revenue	(953)
Cash received for minimum payments	5,935
Balance end of period	$ 16,176
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Deferred revenue		$ (86,774)

Revenue Recognition - Schedul46

Revenue Recognition - Schedule of Annual Minimums by Current Remaining Contract Term (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Average Remaining Contract Term	3 months 18 days
Annual Minimum Payments	$ 6,762
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Average Remaining Contract Term	1 year 7 months 6 days
Annual Minimum Payments	$ 15,761
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Average Remaining Contract Term	8 years 10 months 24 days
Annual Minimum Payments	$ 41,009
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Average Remaining Contract Term	10 years 9 months
Annual Minimum Payments	$ 63,532

Revenue Recognition - Schedul47

Revenue Recognition - Schedule of Segment Revenue from Customers by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	$ 49,850
Gain on asset sales, net	660	$ 44
Construction Aggregates
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	26,424
Gain on asset sales, net	9
Total construction aggregates segment revenues and other income	27,161
Construction Aggregates | Crushed stone, sand and gravel
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	13,739
Construction Aggregates | Delivery and fuel income
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	10,083
Construction Aggregates | Other revenue
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	2,602
Construction Aggregates | Road construction and asphalt paving services
Disaggregation of Revenue [Line Items]
Total coal royalty and other revenues and other income (including affiliates) from contracts with customers	$ 728

Class A Convertible Preferred48

Class A Convertible Preferred Units and Warrants - Preferred Units and Warrants Issued (Details) - USD ($) $ in Thousands	Mar. 02, 2017	Mar. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Preferred Units, net		$ 164,587	$ 173,431
Warrant holders’ interest		$ 66,816	$ 66,816
Preferred Stock
Class of Stock [Line Items]
Transaction price, gross	$ 250,000

Class A Convertible Preferred49

Class A Convertible Preferred Units and Warrants - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 14, 2018	Mar. 02, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
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]
Distributions, Preferred Stock, Paid-in-Kind, Cash Redemption Payment	$ 8,844		$ 8,844	$ 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%	12.00%
Warrants at $34.00 Strike [Member] | Warrant Holders
Class of Stock [Line Items]
Class of Warrant or Right, Warrants Issued			2,250,000
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 34
Preferred Stock
Class of Stock [Line Items]
Transaction price, gross		$ 250,000

Class A Convertible Preferred50

Class A Convertible Preferred Units and Warrants - Financial Position (Details) - USD ($) $ in Thousands	Feb. 14, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Preferred Units, net		$ 164,587		$ 173,431
Preferred Partner | Preferred Stock
Class of Stock [Line Items]
Preferred Units outstanding		250,000,000		258,844,000
Preferred Units, net		$ 164,587		$ 173,431
Class A Convertible Preferred Units
Class of Stock [Line Items]
Distributions, Preferred Stock, Paid-in-Kind, Cash Redemption Payment	$ 8,844	$ 8,844	$ 0

Common and Preferred Unit Dis51

Common and Preferred Unit Distributions Narrative (Details) - USD ($) $ in Thousands	Mar. 02, 2017	Mar. 31, 2018	Mar. 31, 2017
Temporary Equity [Line Items]
Income attributable to preferred unitholders		$ (7,500)	$ (2,500)
Class A Convertible Preferred Units
Temporary Equity [Line Items]
Dividend rate (as a percent)	12.00%	12.00%
General Partner
Temporary Equity [Line Items]
General partner's general partner distribution		2.00%

Common and Preferred Unit Dis52

Common and Preferred Unit Distributions Schedule of Distributions Paid (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 14, 2018	Feb. 14, 2017	Mar. 31, 2018	Mar. 31, 2017
Common unitholders and general partner
Distribution per common unit (in dollars per share)	$ 0.45	$ 0.45
Total distributions paid	$ 5,617	$ 5,615	$ 5,617
Common unitholders
Distributions to common unitholders and general partner	(5,505)	(5,503)
Preferred Partner
Distributions to common unitholders and general partner			(7,765)	$ 0
Total distributions paid			7,765
General Partner
Distributions to common unitholders and general partner			$ (5,617)	$ (5,615)
Distributions paid to general partners	$ 112	$ 112
Preferred Stock | Preferred Partner
Distribution per common unit (in dollars per share)	$ 30
Distributions to common unitholders and general partner	$ (7,765)
Total Distribution Declared	$ 7,765

Net Income Per Common Unit (Det

Net Income Per Common Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Allocation of net income:
Net income from continuing operations	$ 26,088		$ 6,111
Less: income attributable to preferred unitholders	7,500		2,500
Less: net income from continuing operations and income attributable to preferred unitholders allocated to the general partner	371		4
Net income from continuing operations attributable to common unitholders	18,217		3,607
Net loss from discontinued operations	(14)		(207)
Less: net loss from discontinued operations attributable to the general partner	0		(4)
Net loss from discontinued operations attributable to common unitholders	(14)		(203)
Net Income	26,074	[1]	5,904
Less: net income and income attributable to preferred unitholders allocated to the general partner	371		0
Net income attributable to common unitholders	$ 18,203		$ 3,404
Basic Income (Loss) per Unit:
Weighted average common units (in shares)	12,238		12,232
Basic net income from continuing operations per common unit	$ 1.49		$ 0.30
Basic net loss from discontinued operations per common unit	0		(0.02)
Basic net income per common unit	$ 1.49		$ 0.28
Diluted income (loss) per common unit:
Dilutive effect of Warrants (in shares)	424		322
Dilutive effect of Preferred Units (in shares)	9,463		2,391
Weighted average common units—diluted (in shares)	22,125		14,945
Less: net income from continuing operations allocated to the general partner	$ 521		$ 53
Diluted net income from continuing operations attributable to common unitholders	25,567		6,058
Diluted net loss from discontinued operations attributable to common unitholders	(14)		(203)
Less: net income allocated to the general partner	521		49
Diluted net income attributable to common unitholders	$ 25,553		$ 5,855
Diluted net income (loss) per common unit from continuing operations (in dollars per share)	$ 1.16		$ 0.30
Diluted net loss from discontinued operations per common unit (in dollars per share)	0		(0.02)
Diluted net income per common unit (in dollars per share)	$ 1.15		$ 0.28
Warrant Holders | Warrants at $34.00 Strike [Member]
Class of Warrant or Right, Warrants Issued	2,250
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 34
[1]	Net income includes $7.5 million attributable to Preferred Unitholders that accumulated during the period, of which $7.4 million is allocated to the common unitholders and $0.2 million is allocated to the general partner.

Segment Information - Additiona

Segment Information - Additional Information (Details) - segment	3 Months Ended
	Mar. 31, 2018	Jul. 31, 2013	Jan. 31, 2013
Segment Reporting Information [Line Items]
Number of operating segments	3
Ciner Wyoming
Segment Reporting Information [Line Items]
Percentage of partnership interest owned (percent)	49.00%	49.00%	48.51%

Segment Information - Schedule

Segment Information - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues and other income	$ 88,366	$ 88,653
Gain on asset sales, net	660	44
Operating and maintenance expenses (including affiliates)	32,433	32,183
General and administrative (including affiliates)	4,336	7,202
Depreciation, depletion and amortization (including affiliates)	7,957	10,492
Asset impairments	242	1,778
Other expense, net	17,970	30,931
Net income (loss) from continuing operations	26,088	6,111
Net loss from discontinued operations	(14)	(207)
Total assets	1,377,206		$ 1,389,164
Corporate and Financing
Segment Reporting Information [Line Items]
Revenues and other income	0	0
Gain on asset sales, net	0	0
Operating and maintenance expenses (including affiliates)	0	0
General and administrative (including affiliates)	4,336	7,202
Depreciation, depletion and amortization (including affiliates)	0	0
Asset impairments	0	0
Other expense, net	(17,950)	30,536
Net income (loss) from continuing operations	(22,286)	(37,738)
Net income (loss) from discontinued operations	0	0
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues and other income	0	0
Coal Royalty and Other
Segment Reporting Information [Line Items]
Revenues and other income	45,973	34,994
Coal Royalty and Other | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income	51,593	51,138
Gain on asset sales, net	651	29
Operating and maintenance expenses (including affiliates)	6,215	7,384
General and administrative (including affiliates)	0	0
Depreciation, depletion and amortization (including affiliates)	5,100	6,973
Asset impairments	242	1,778
Other expense, net	0	0
Net income (loss) from continuing operations	40,728	35,094
Net income (loss) from discontinued operations	0	0
Coal Royalty and Other | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues and other income	41	62
Soda Ash
Segment Reporting Information [Line Items]
Revenues and other income	9,621	10,294
Soda Ash | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income	9,621	10,294
Gain on asset sales, net	0	0
Operating and maintenance expenses (including affiliates)	0	0
General and administrative (including affiliates)	0	0
Depreciation, depletion and amortization (including affiliates)	0	0
Asset impairments	0	0
Other expense, net	0	0
Net income (loss) from continuing operations	9,621	10,294
Net income (loss) from discontinued operations	0	0
Soda Ash | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues and other income	0	0
Construction Aggregates
Segment Reporting Information [Line Items]
Revenues and other income	26,424	25,483
Gain on asset sales, net	9
Construction Aggregates | Operating Segments
Segment Reporting Information [Line Items]
Revenues and other income	27,152	27,221
Gain on asset sales, net	9	15
Operating and maintenance expenses (including affiliates)	26,218	24,799
General and administrative (including affiliates)	0	0
Depreciation, depletion and amortization (including affiliates)	2,857	3,519
Asset impairments	0	0
Other expense, net	(20)	(395)
Net income (loss) from continuing operations	(1,975)	(1,539)
Net income (loss) from discontinued operations	0	0
Construction Aggregates | Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues and other income	(41)	$ (62)
Continuing Operations
Segment Reporting Information [Line Items]
Total assets	1,376,215		1,388,173
Continuing Operations | Corporate and Financing
Segment Reporting Information [Line Items]
Total assets	4,856		6,129
Continuing Operations | Coal Royalty and Other | Operating Segments
Segment Reporting Information [Line Items]
Total assets	943,334		945,237
Continuing Operations | Soda Ash | Operating Segments
Segment Reporting Information [Line Items]
Total assets	241,679		245,433
Continuing Operations | Construction Aggregates | Operating Segments
Segment Reporting Information [Line Items]
Total assets	186,346		191,374
Discontinued Operations
Segment Reporting Information [Line Items]
Total assets	991		991
Discontinued Operations | Corporate and Financing
Segment Reporting Information [Line Items]
Total assets	0		0
Discontinued Operations | Coal Royalty and Other | Operating Segments
Segment Reporting Information [Line Items]
Total assets	0		0
Discontinued Operations | Soda Ash | Operating Segments
Segment Reporting Information [Line Items]
Total assets	0		0
Discontinued Operations | Construction Aggregates | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 0		$ 0

Equity Investment - Additional

Equity Investment - Additional Information (Detail)	Mar. 31, 2018	Jul. 31, 2013	Jan. 31, 2013
Ciner Wyoming
Schedule of Equity Method Investments [Line Items]
Percentage of partnership interest owned (percent)	49.00%	49.00%	48.51%

Equity Investment - Schedule o

Equity Investment - Schedule of Summarized Financial Information of Unaudited Financial Statements (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Equity Method Investments [Roll Forward]
Balance at beginning of period	$ 245,433		$ 255,901
Comprehensive loss from unconsolidated investment	24,949		4,772
Balance at end of period	241,679		252,803
Net Income	26,074	[1]	5,904
Ciner Wyoming
Equity Method Investments [Roll Forward]
Income allocation to NRP’s equity interests	10,832		11,480
Amortization of basis difference	1,211		1,186
Comprehensive loss from unconsolidated investment	(1,125)		(1,142)
Cash Dividends Paid to Parent Company by Unconsolidated Subsidiaries	(12,250)		(12,250)
Sales	121,219		126,572
Gross profit	28,222		28,697
Net Income	$ 22,107		$ 23,428
[1]	Net income includes $7.5 million attributable to Preferred Unitholders that accumulated during the period, of which $7.4 million is allocated to the common unitholders and $0.2 million is allocated to the general partner.

Plant and Equipment - Plant and

Plant and Equipment - Plant and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Plant and equipment	$ 87,197	$ 84,173
Construction in process	1,169	803
Less accumulated depreciation	(41,129)	(38,806)
Total plant and equipment, net	$ 47,237	$ 46,170

Plant and Equipment - Additiona

Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation expense on plant and equipment	$ 2.4	$ 3

Mineral Rights - Mineral Rights

Mineral Rights - Mineral Rights (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	$ 1,346,061	$ 1,346,309
Accumulated Depletion	(467,216)	(462,424)
Net Book Value	878,845	883,885
Coal Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	1,169,861	1,170,104
Accumulated Depletion	(440,599)	(436,964)
Net Book Value	729,262	733,140
Aggregate Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	150,642	150,642
Accumulated Depletion	(17,754)	(16,836)
Net Book Value	132,888	133,806
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	(7,375)	(7,158)
Net Book Value	5,020	5,237
Other Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Carrying Value	13,163	13,168
Accumulated Depletion	(1,488)	(1,466)
Net Book Value	11,675	$ 11,702
Hillsboro Property [Member] | Coal Mineral Rights
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Net Book Value	$ 235,000

Mineral Rights - Additional Inf

Mineral Rights - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)
Total depletion and amortization expense on mineral interests	$ 4,800	$ 6,600
Asset impairments	242	$ 1,778
Mineral rights, net	878,845		$ 883,885
Coal Mineral Rights
Mineral rights, net	729,262		733,140
Oil And Gas Mineral Rights
Mineral rights, net	5,020		5,237
Other Mineral Rights
Mineral rights, net	$ 11,675		$ 11,702
Hillsboro Property [Member] | Coal Mineral Rights
Mineral Rights, Tons	179,000
Asset impairments	$ 0
Mineral rights, net	$ 235,000

Intangible Assets - Intangible

Intangible Assets - Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 86,336	$ 86,336
Less accumulated amortization	(37,567)	(36,782)
Total intangible assets, net	$ 48,769	$ 49,554

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Intangible Assets [Line Items]
Amortization expense—affiliate	$ 0	$ 768
Amortization expense	$ 800	$ 200

Debt - Debt (Detail)

Debt - Debt (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal balance	$ 822,044,000	$ 827,844,000
Net unamortized debt discount	(1,562,000)	(1,661,000)
Net unamortized debt issuance costs	(15,905,000)	(16,835,000)
Total debt	804,577,000	809,348,000
Less - current portion of long term debt	79,723,000	79,740,000
Total long-term debt, net	724,854,000	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 | Senior Notes
Debt Instrument [Line Items]
Principal balance	381,400,000	422,200,000
Opco | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Floating rate revolving credit facility	150,000,000
Principal balance	95,000,000	60,000,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 55,000,000
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	$ 4,586,000	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	$ 21,334,000	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	$ 22,946,000	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	$ 16,115,000	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	$ 44,693,000	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	$ 89,589,000	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	$ 27,200,000	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	$ 120,547,000	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	$ 34,396,000	$ 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%

Debt - Additional Information (

Debt - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Debt issuance cost capitalized	$ 15,905,000			$ 16,835,000
Principal balance	822,044,000			827,844,000
Senior Notes due 2022
Debt Instrument [Line Items]
Principal balance	$ 331,309,000			330,404,000
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
Opco | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Interest Rate During Period	5.91%	5.22%
Debt issuance cost capitalized	$ 3,900,000			4,600,000
Collateral carrying amount	$ 646,300,000			649,700,000
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]
Rate of senior notes	8.38%
Principal balance	$ 21,334,000			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	$ 27,200,000			31,733,000
Opco | Senior Notes
Debt Instrument [Line Items]
Principal balance	381,400,000			422,200,000
Principal payments on its senior notes	$ 40,800,000	$ 40,800,000
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	$ 150,000,000
Principal balance	95,000,000			$ 60,000,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 55,000,000
Opco | Scenario, Forecast [Member] | Floating Rate Revolving Credit Facility Due April Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Floating rate revolving credit facility			$ 100,000,000

Fair Value Measurements - Contr

Fair Value Measurements - Contracts Receivable and Debt (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	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	822,044,000		$ 827,844,000
Contracts receivable—affiliate, current and long-term	43,312,000		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]
Contracts receivable—affiliate, current and long-term	30,332,000		30,517,000
Senior Notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	331,309,000		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	371,561,000		366,376,000
Opco Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	378,268,000		418,944,000
Opco Senior Notes | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value	410,011,000		447,538,000
Opco Revolving Credit Facility And Term Loan Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying Value	95,000,000		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	$ 95,000,000		$ 60,000,000

Fair Value Measurements - Embed

Fair Value Measurements - Embedded Derivatives (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Embedded Derivative, Fair Value of Embedded Derivative Liability	$ 0	$ 0

Related Party Transactions - Su

Related Party Transactions - Summary of Reimbursements (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Amount payable to related parties	$ 2,093		$ 562
Operating and maintenance expenses—affiliates	2,465	$ 2,555
General and administrative—affiliates	931	1,124
Revenue, Net	88,366	88,653
Cline Affiliates
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates	0	335
Affiliated Entity | Western Pocahontas Properties and Quintana Minerals Corporation [Member]
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates	1,907	$ 2,135
Quintana Minerals
Related Party Transaction [Line Items]
Amount payable to related parties	1,100		400
Western Pocahontas Properties
Related Party Transaction [Line Items]
Amount payable to related parties	$ 1,000		$ 100

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	May 09, 2017	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Operating Expenses		$ 44,968,000	$ 51,655,000
Accounts receivable, net		55,651,000		$ 50,505,000	$ 47,026,000
Amount payable to related parties		2,093,000			562,000
Operating and maintenance expenses—affiliates		2,465,000	2,555,000
Revenues and other income		88,366,000	88,653,000
Operating and maintenance expenses		29,968,000	29,628,000
Accounts receivable—affiliates		94,000			161,000
Intangible assets, net		48,769,000			49,554,000
Long-term contracts receivable		40,331,000			40,776,000
Deferred revenue		14,622,000		$ 11,858,000	100,605,000
Quintana Minerals
Related Party Transaction [Line Items]
Amount payable to related parties		1,100,000			400,000
Western Pocahontas Properties
Related Party Transaction [Line Items]
Amount payable to related parties		1,000,000			100,000
Cline Affiliates
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates		$ 0	335,000
Rate of interest in the partnerships general partner	31.00%	31.00%
Foresight Energy Lp
Related Party Transaction [Line Items]
Operating Expenses		$ 401,000	0
Operating and maintenance expenses		401,000	335,000
Foresight Energy Lp | Coal Sales
Related Party Transaction [Line Items]
Coal royalty and other—affiliates		0	11,152,000
Revenues		7,048,000	0
Sugar Camp
Related Party Transaction [Line Items]
Unearned income		27,526,000			28,366,000
Net amount receivable		70,225,000			71,452,000
Corsa
Related Party Transaction [Line Items]
Accounts receivable—affiliates		100,000			200,000
Royalty Revenue from Coal		200,000	400,000
Western Pocahontas Properties Limited Partnership | Affiliated Entity
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates		600,000	100,000
Other assets—affiliate					$ 200,000
Foresight Energy Lp
Related Party Transaction [Line Items]
Revenues		12,431,000	15,791,000
Transportation and Processing | Foresight Energy Lp | Coal Sales
Related Party Transaction [Line Items]
Revenues and other income		5,383,000	0
Transportation and Processing - Affiliates | Foresight Energy Lp | Coal Sales
Related Party Transaction [Line Items]
Coal royalty and other—affiliates		0	4,639,000
Coal Royalty and Other
Related Party Transaction [Line Items]
Revenues and other income		45,973,000	34,994,000
Coal royalty and other—affiliates		237,000	11,505,000
Coal Royalty and Other | Transportation and Processing
Related Party Transaction [Line Items]
Revenues and other income		5,383,000	0
Coal Royalty and Other | Transportation and Processing - Affiliates
Related Party Transaction [Line Items]
Coal royalty and other—affiliates		$ 0	$ 4,639,000

Major Customers (Detail)

Major Customers (Detail) - Foresight Energy Lp - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Concentration Risk [Line Items]
Revenues	$ 12,431	$ 15,791
Sales Revenue | Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	14.00%	17.80%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	36 Months Ended
	Mar. 31, 2018	Dec. 31, 2015	Jul. 31, 2013	Jan. 31, 2013
Lawsuit Against Macoupin Energy, LLC
Commitments And Contingencies [Line Items]
Damages sought, value	$ 9.5
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
Ciner Wyoming
Commitments And Contingencies [Line Items]
Percentage of partnership interest owned (percent)	49.00%		49.00%	48.51%
Pending Litigation [Member] | Lawsuit Against Hillsboro Energy LLC
Commitments And Contingencies [Line Items]
Minimum quarterly deficiency payments	$ 7.5
Loss Contingency, Loss in Period, Interest	12.8
Loss Contingency, Loss in Period	83.5
Pending Litigation [Member] | Minimum | Anadarko Holding Company
Commitments And Contingencies [Line Items]
Minimum deficiency payments	0
Pending Litigation [Member] | Maximum | Anadarko Holding Company
Commitments And Contingencies [Line Items]
Minimum deficiency payments	$ 40

Unit-Based Compensation (Detail

Unit-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 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, Number of Shares Authorized	800,000
Share-based Compensation Arrangement by Share-based Payment Award, Terms of Award	P10Y
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	61,000	0
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, Grants in Period, Gross	75,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 29.16
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	14,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$ 29.44
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 0
Stock Granted, Value, Share-based Compensation, Gross	$ 2.2
Allocated Share-based Compensation Expense	0.6
Unaccrued Cost Associated With Outstanding Grants And Related Distribution Equivalent Rights	$ 1.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	2 years 10 months 24 days
Board Members [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Granted, Value, Share-based Compensation, Gross	$ 0.6

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] $ / shares in Units, $ in Millions	Apr. 25, 2018USD ($)$ / shares
Subsequent Event [Line Items]
Distribution Made to Limited Partner, Distributions Paid, Per Unit | $ / shares	$ 0.45
Dividend rate (as a percent)	12.00%
Dividends, Preferred Stock | $	$ 7.5

Uncategorized Items - nrp-20180

Label	Element	Value
General Partner [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,805,000
Common Stock [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	88,448,000
Partners Capital Excluding Noncontrolling Interest [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 90,253,000