Terra Nitrogen Co L P 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 21, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	TERRA NITROGEN CO L P /DE
Entity Central Index Key	879,575
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 396,034,573
Entity Common Stock, Shares Outstanding		18,501,576
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 81.5	$ 39.5
Due from affiliates of the General Partner	17.1	4
Accounts receivable	0.9	0.6
Inventories	5.3	8.6
Prepaid expenses and other current assets	0.3	7.9
Total current assets	105.1	60.6
Property, plant and equipment—net	290.2	301.3
Other assets	8.6	11.4
Total assets	403.9	373.3
Current liabilities:
Accounts payable and accrued expenses	27.4	27.8
Due to affiliates of the General Partner	4.2	4.1
Other current liabilities	3.2	0
Total current liabilities	34.8	31.9
Other liabilities	1	2.6
Partners' capital:
General partner's interest	64.8	50.3
Total partners' capital	368.1	338.8
Total liabilities and partners' capital	403.9	373.3
Common
Partners' capital:
Limited partners' interests, 18,501,576 Common Units authorized, issued and outstanding; 184,072 Class B Common Units authorized, issued and outstanding	301.2	286.7
Class B Common
Partners' capital:
Limited partners' interests, 18,501,576 Common Units authorized, issued and outstanding; 184,072 Class B Common Units authorized, issued and outstanding	$ 2.1	$ 1.8

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2017	Dec. 31, 2016
Common
Limited partners' interests, Common Units authorized	18,501,576	18,501,576
Common Units issued	18,501,576	18,501,576
Common Units outstanding	18,501,576	18,501,576
Class B Common
Limited partners' interests, Common Units authorized	184,072	184,072
Common Units issued	184,072	184,072
Common Units outstanding	184,072	184,072

Consolidated Statements Of Oper

Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales:
Other income	$ 0.5	$ 0	$ 0.9
Total	397.2	418.3	581.7
Cost of goods sold:
Materials, supplies and services	212.6	163.6	228
Gross margin	156.7	226.8	325.8
Other general and administrative expenses	1.7	1.9	3.2
Gain on sale of equity method investment	(14.3)	0	0
Operating Income (Loss)	153.4	209.2	306.9
Interest Income, Other	0.5	0.1	0
Net earnings	153.9	209.3	306.9
Allocation of net earnings:
Net earnings	$ 153.9	$ 209.3	$ 306.9
Net earnings per Common Unit (in dollars per unit)	$ 5.93	$ 7.56	$ 10.06
Affiliate of General Partner
Net sales:
Product sales to affiliates of the General Partner	$ 396.1	$ 417.7	$ 580.2
Other income	0.6	0.6	0.6
Cost of goods sold:
Services provided by affiliates of the General Partner	27.9	27.9	27.9
Selling, general and administrative services provided by affiliates of the General Partner	15.9	15.7	15.7
General Partner's Interest
Allocation of net earnings:
Net Income Allocated to General Partners	42.6	67.4	117.7
Common Units | Class B Common
Allocation of net earnings:
Net Income Allocated to Limited Partners	1.5	2	3
Common Units | Common units
Allocation of net earnings:
Net Income Allocated to Limited Partners	$ 109.8	$ 139.9	$ 186.2

Consolidated Statements Of Part

Consolidated Statements Of Partners' Capital - USD ($) $ in Millions	Total	General Partner's Interest	Common unitsCommon Units	Class B Common UnitsCommon Units
Partners' capital at Dec. 31, 2014	$ 374.9	$ 70	$ 302.7	$ 2.2
Increase (Decrease) in Partners' Capital
Net earnings allocated			186.2	3
Net Income Allocated to General Partners		117.7
Net earnings	306.9
Distributions	(294.8)	(111.5)	(180.4)	(2.9)
Partners' capital at Dec. 31, 2015	387	76.2	308.5	2.3
Increase (Decrease) in Partners' Capital
Net earnings allocated			139.9	2
Net Income Allocated to General Partners		67.4
Net earnings	209.3
Distributions	(257.5)	(93.3)	(161.7)	(2.5)
Partners' capital at Dec. 31, 2016	338.8	50.3	286.7	1.8
Increase (Decrease) in Partners' Capital
Net earnings allocated			109.8	1.5
Net Income Allocated to General Partners		42.6
Net earnings	153.9
Distributions	(124.6)	(28.1)	(95.3)	(1.2)
Partners' capital at Dec. 31, 2017	$ 368.1	$ 64.8	$ 301.2	$ 2.1

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net earnings	$ 153.9	$ 209.3	$ 306.9
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	39	40.4	35.8
Unrealized loss (gain) on derivatives	10.6	(35.3)	24.3
Loss on disposal of property, plant and equipment	0	0.1	2
Gain on sale of equity method investment	(14.3)	0	0
Changes in operating assets and liabilities:
Accounts receivable	(0.3)	0.2	(0.4)
Inventories	3.3	2	(1.1)
Accounts payable and accrued expenses	(0.9)	2.5	(6.7)
Due to/from affiliates of the General Partner	(13)	6	15.1
Other assets and liabilities	(0.8)	(1.7)	(0.8)
Net cash provided by operating activities	177.5	223.5	375.1
Investing Activities:
Additions to property, plant and equipment	(27.2)	(33.1)	(87.8)
Proceeds from Sale of Property, Plant, and Equipment	0	0.2	0.9
Proceeds from sale of equity method investment	16.3	0	0
Net cash used in investing activities	(10.9)	(32.9)	(86.9)
Financing Activities:
Net cash used in financing activities	(124.6)	(257.5)	(294.8)
Increase (decrease) in cash and cash equivalents	42	(66.9)	(6.6)
Cash and cash equivalents at beginning of year	39.5	106.4	113
Cash and cash equivalents at end of year	81.5	39.5	106.4
Declared and paid partnership distributions	$ 124.6	$ 257.5	$ 294.8

Background and Basis of Present

Background and Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background and Basis of Presentation	Background and Basis of Presentation Terra Nitrogen Company, L.P. ("TNCLP," "we," "our" or "us") is a Delaware limited partnership that produces nitrogen fertilizer products. Our principal products are anhydrous ammonia (ammonia) and urea ammonium nitrate solution (UAN), which we manufacture at our facility in Verdigris, Oklahoma. We conduct our operations through an operating partnership, Terra Nitrogen, Limited Partnership (TNLP or the Operating Partnership, and collectively with TNCLP, the Partnership). We own a 99% limited partner interest in the Operating Partnership, and Terra LP Holdings LLC (TLPH), an affiliate of the General Partner, owns a 0.975% limited partner interest. Terra Nitrogen GP Inc. (TNGP or the General Partner), a Delaware corporation, is the general partner of both TNCLP and TNLP and owns a 0.025% general partner interest in each of TNCLP and TNLP. The General Partner is an indirect, wholly owned subsidiary of CF Industries Holdings, Inc. (CF Industries), a Delaware corporation. Throughout this document, the term "affiliates of the General Partner" refers to consolidated subsidiaries of CF Industries, including TNGP. Ownership of TNCLP is composed of the general partner interest and the limited partner interests. The general partner interest in TNCLP is represented by 4,720 general partner units. Limited partner interests are represented by common units, which are listed for trading on the New York Stock Exchange (NYSE) under the symbol "TNH", and Class B common units. As of December 31, 2017 , we had 18,501,576 common units and 184,072 Class B common units issued and outstanding. CF Industries through its subsidiaries owned 13,889,014 common units (representing approximately 75.1% of the total outstanding common units) and all of the Class B common units as of December 31, 2017 . On February 7, 2018, TNCLP announced that, in accordance with Section 17.1 of TNCLP’s First Amended and Restated Agreement of Limited Partnership, as amended (the TNCLP Partnership Agreement), TNGP elected to exercise the right, assigned to TNGP by TNCLP, to purchase all of the issued and outstanding common units representing limited partner interests in TNCLP not already owned by TNGP or its affiliates (the Public Units). For additional information, see Note 15—Subsequent Event. We are a master limited partnership (MLP). Partnerships are generally not subject to federal income tax, although publicly traded partnerships (such as TNCLP) are treated as corporations for federal income tax purposes (and therefore are subject to federal income tax), unless at least 90% of the partnership's gross income is "qualifying income" as defined in Section 7704 of the Internal Revenue Code of 1986, as amended, and the partnership is not required to register as an investment company under the Investment Company Act of 1940. As we currently satisfy the requirements to be treated as a partnership for federal income tax purposes, no federal income taxes are paid by the Partnership. On January 19, 2017, the Internal Revenue Service (IRS) issued final regulations on the types of income and activities that constitute or generate qualifying income of a MLP. For calendar year MLPs, the effective date of the regulations is January 1, 2018. The regulations have the effect of limiting the types of income and activities that qualify under the MLP rules, subject to certain transition provisions. The regulations define the activities that generate qualifying income from certain processing or refining and transportation activities with respect to any mineral or natural resource (including fertilizer) as activities that generate qualifying income, but the regulations reserve on specifics regarding fertilizer-related activities. However, the IRS has issued two private letter rulings to taxpayers in the fertilizer industry unrelated to TNCLP (one before and one after the issuance of the final regulations) which would indicate that each taxpayer's fertilizer manufacturing activities should produce qualifying income for purposes of determining whether 90% of the partnership's gross income is qualifying income under the final regulations. The entities to which these private letter rulings were issued would appear to operate nitrogen fertilizer manufacturing businesses that are similar to ours. While these private letter rulings provide some insight into the manner in which the IRS analyzed fertilizer manufacturing activities at the time these rulings were issued, these private letter rulings are specific to different entities. Thus, the IRS is not bound to follow them in respect of TNCLP, nor may we rely on them as precedent when determining whether we satisfy the MLP 90% gross income test. Any change in the federal income tax treatment of income from fertilizer-related activities as qualifying income could have a material impact on the taxation of the Partnership and could have a material adverse impact on unitholder distributions. We continue to monitor these IRS regulatory activities. The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (U.S. GAAP).

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Consolidation The consolidated financial statements of TNCLP and the accompanying notes include the accounts of the Partnership. All intercompany transactions and balances have been eliminated. Income is allocated to the General Partner and the limited partners of TNCLP (Limited Partners) in accordance with the provisions of the TNCLP Partnership Agreement that provides for allocations of income between the Limited Partners and the General Partner in the same proportion as cash distributions related to such year. The 0.975% limited partner interest and the 0.025% general partner interest in the Operating Partnership held by TLPH and the General Partner, respectively, are included in the line labeled General Partner’s interest in the consolidated financial statements. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses for the periods presented. Actual results could differ from these estimates. Significant estimates and assumptions are used for, but are not limited to, the net realizable value of inventories, environmental remediation liabilities, environmental and litigation contingencies, useful lives of property, plant and equipment, the assumptions used in the evaluation of potential impairments of property, plant and equipment and the allowance for doubtful accounts receivable. Revenue Recognition The primary products we sell are ammonia and UAN. Sales are made in accordance with the Amendment to the General and Administrative Services and Product Offtake Agreement (the Services and Offtake Agreement) we have with an affiliate of the General Partner under which affiliates of the General Partner purchase our products. We recognize revenue as products are shipped from the plant gate when title and risk of loss transfer to affiliates of the General Partner. The Services and Offtake Agreement is accounted for as an operating lease comprised entirely of variable lease payments associated with the sale of our products. The Services and Offtake Agreement is described in Note 10—Related Party Transactions . Cash and Cash Equivalents Cash and cash equivalents include highly liquid investments that are readily convertible to known amounts of cash with original maturities of three months or less. The carrying value of cash and cash equivalents approximates fair value. Due to/from Affiliates of the General Partner We receive cash and make expenditures directly from our cash accounts. Because we sell our products to and receive labor and other services from affiliates of the General Partner, the affiliates of the General Partner continue to be both debtors and creditors to us. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at face amounts less an allowance for doubtful accounts. The allowance is an estimate based on historical collection experience, current economic and market conditions, and a review of the current status of each customer's trade accounts receivable. A receivable is past due if payments have not been received within the agreed upon invoice terms. Account balances are charged-off against the allowance when management determines that it is probable the receivable will not be recovered. Inventories Inventories are reported at the lower of cost and net realizable value and are determined on a first-in, first-out (FIFO) and average cost basis. Inventories include the cost of materials, production labor and production overhead. Net realizable value is reviewed quarterly. Fixed production costs related to idle capacity are not included in the cost of inventories but are charged directly to cost of sales. On January 1, 2017, we adopted Accounting Standards Update (ASU) No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, as discussed in Note 3—New Accounting Standards . Property, Plant and Equipment Property, plant and equipment are stated at cost and are subject to the Services and Offtake Agreement, which is accounted for as an operating lease, as described in Note 10—Related Party Transactions . Depreciation and amortization are computed using the straight-line method over the estimated useful life of the property, plant and equipment. Useful lives for property, plant, and equipment range from 10 to 40 years for buildings and 3 to 30 years for machinery and equipment. We periodically review these useful lives and change the estimates to reflect the results of those reviews. Scheduled inspections, replacements and overhauls of machinery and equipment at our continuous process manufacturing facility are referred to as plant turnarounds. Plant turnarounds are accounted for under the deferral method, as opposed to the direct expense or built-in overhaul methods. Under the deferral method, expenditures related to turnarounds are capitalized when incurred and amortized to production costs on a straight-line basis over the period benefited, which is until the next scheduled turnaround in up to 5 years . If the direct expense method were used, all turnaround costs would be expensed as incurred. Internal employee costs and overhead amounts are not considered turnaround costs and are not capitalized. Turnaround costs are classified as investing activities in our consolidated statements of cash flows. For additional information, see Note 9—Property, Plant and Equipment—Net . Recoverability of Long-Lived Assets We review property, plant and equipment and other long-lived assets in order to assess recoverability based on expected future undiscounted cash flows whenever events or circumstances indicate that the carrying value may not be recoverable. If the sum of the expected future net cash flows is less than the carrying value, an impairment loss is recognized. The impairment loss is measured as the amount by which the carrying value exceeds the fair value of the asset. Other Leases Leases are classified as either operating leases or capital leases. Assets acquired under capital leases are depreciated on the same basis as property, plant and equipment. We currently do not have any capital leases. Rental payments, including rent holidays, leasehold incentives, and scheduled rent increases, if any, are expensed on a straight-line basis over the lease term. Income Taxes As a partnership, we are not subject to income taxes. For additional information, see Note 1—Background and Basis of Presentation . The income tax liability of the individual partners is not reflected in our consolidated financial statements. Derivative Financial Instruments Natural gas is the principal raw material used to produce nitrogen fertilizers. We use natural gas both as a chemical feedstock and as a fuel to produce ammonia and UAN. We manage the risk of changes in natural gas prices primarily through the use of derivative financial instruments. The derivative instruments that we use are primarily natural gas fixed price swaps and options traded in the over-the-counter markets. These derivatives reference NYMEX futures contract prices, which represent the basis for fair value at any given time. The derivatives are traded in months forward and settlements are scheduled to coincide with anticipated gas purchases during those future periods. We do not use derivatives for trading purposes and are not a party to any leveraged derivatives. We have elected to not apply hedge accounting to our derivatives; as a result, changes in the fair value of the derivatives are recorded in cost of goods sold in our consolidated statements of operations. Derivatives are recognized in our consolidated balance sheets at fair value. Cash flows related to natural gas derivatives are reported as operating activities in our consolidated statements of cash flows. For additional information, see Note 7—Derivative Financial Instruments . Asset Retirement Obligations Asset retirement obligations (AROs) are legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development or normal operation of such assets. AROs are initially recognized as liabilities as incurred when sufficient information exists to estimate fair value. When initially recognized, the fair value based on discounted future cash flows is recorded both as a liability and an increase in the carrying amount of the related long-lived asset. In subsequent periods, depreciation of the asset and accretion of the liability are recorded. For additional information on AROs, see Note 11—Asset Retirement Obligations . Environmental Environmental expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations are expensed. Expenditures that increase the capacity or extend the useful life of an asset, improve the safety or efficiency of the operations, or mitigate or prevent future environmental contamination are capitalized. Liabilities are recorded when it is probable that a liability has been incurred, the costs can be reasonably estimated, and the liability would not be discounted. Litigation From time to time, the Partnership is subject to ordinary, routine legal proceedings related to the usual conduct of its business. From time to time, the Partnership also is involved in legal proceedings regarding public utility and transportation rates, environmental matters, taxes and permits relating to the operations of its plant and facilities. Accruals for such contingencies are recorded to the extent management concludes their occurrence is probable and the financial impact of an adverse outcome is reasonably estimable. Disclosure for specific legal contingencies is provided if the likelihood of occurrence is at least reasonably possible and the exposure is considered material to the consolidated financial statements. In making determinations of likely outcomes of litigation matters, many factors are considered. These factors include, but are not limited to, past history, scientific and other evidence, and the specifics and status of each matter. If the assessment of various factors changes, the estimates may change. Predicting the outcome of claims and litigation, and estimating related costs and exposure involves substantial uncertainties that could cause actual costs to vary materially from estimates and accruals. Legal fees are expensed as incurred and are included in selling, general, and administrative services provided by affiliates of the General Partner in our consolidated statements of operations.

New Accounting Standards

New Accounting Standards	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Standards	New Accounting Standards Recently Adopted Pronouncement On January 1, 2017, we adopted ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory. ASU No. 2015-11 changes the inventory measurement principle for entities using the FIFO or average cost methods. For entities utilizing one of these methods, the inventory measurement principle changed from the lower of cost or market to the lower of cost and net realizable value. We follow the FIFO and average cost methods, and the adoption of this ASU did not have a material effect on our consolidated financial statements. Recently Issued Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued ASU No. 2014-09, Revenue from Contracts with Customers, (Topic 606), which supersedes the revenue recognition requirements in Accounting Standards Codification (ASC) Topic 605, Revenue Recognition. This ASU is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments. Additionally, the costs to obtain and fulfill a contract, including assets to be recognized, are to be capitalized and such capitalized costs are to be disclosed. All of our nitrogen fertilizer production is sold to affiliates of the General Partner. The Services and Offtake Agreement, under which all of our nitrogen fertilizer products are sold, is accounted for as an operating lease comprised entirely of variable lease payments associated with the sale of our nitrogen fertilizer products, therefore, it does not meet the definition of a contract as defined by ASU No. 2014-09. As such, our adoption of ASU No. 2014-09 on January 1, 2018 did not have a material impact on our consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which supersedes the lease accounting requirements in ASC Topic 840, Leases. This ASU will require lessees to recognize the rights and obligations resulting from virtually all leases (other than leases that meet the definition of a short-term lease) on their balance sheets as right-of-use assets with corresponding lease liabilities. For lessors, ASU No. 2016-02 leaves the current lessor accounting in ASC Topic 840 largely unchanged. Quantitative and qualitative disclosures, including significant judgments made by management, will be required. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted, and requires the modified retrospective method of adoption. Under ASU No. 2016-02, and consistent with the current accounting treatment under ASC Topic 840, we expect that the Services and Offtake Agreement will continue to be accounted for as an operating lease. We expect the adoption of this ASU will not have a material impact on our consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities, which expands and refines hedge accounting for both financial and non-financial risk components, aligns the recognition and presentation of the effects of hedging instruments and hedged items in the financial statements, and includes certain targeted improvements to ease the application of current guidance related to the assessment of hedge effectiveness. This ASU is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted in any interim period. We do not expect the adoption of this ASU will have a material effect on our consolidated financial statements.

Agreement of Limited Partnershi

Agreement of Limited Partnership	12 Months Ended
	Dec. 31, 2017
Distributions Made to Members or Limited Partners [Abstract]
Agreement of Limited Partnership	Agreement of Limited Partnership Ownership of TNCLP is composed of the general partner interest and the limited partner interests (see Note 1—Background and Basis of Presentation ). Holders of common units and Class B common units do not have preemptive rights. Holders of common units are entitled to one vote per common unit with respect to each matter on which holders of common units are entitled to vote. The Class B common units have no voting rights on any matter. Unitholders have only limited voting rights on matters affecting our business and, therefore, limited ability to influence management's decisions regarding our business. Unitholders have no right to elect the General Partner or the TNGP Board of Directors on an annual or other continuing basis. Furthermore, the General Partner may only be removed by a vote of the holders of at least 66 2/3% of our outstanding common units, including any common units held by the General Partner and its affiliates (including CF Industries). Given that the General Partner and its affiliates own approximately 75.1% of our outstanding common units, holders of our publicly traded common units are not able to remove the General Partner under any circumstances. The General Partner and its affiliates own approximately 75.1% of our outstanding common units. When not more than 25% of our issued and outstanding common units are held by persons other than the General Partner and its affiliates (collectively, non-affiliated persons), as was the case at December 31, 2017 , we, at the General Partner's sole discretion, may call, or assign to the General Partner or its affiliates, our right to acquire all, but not less than all, such outstanding common units held by non-affiliated persons. On February 7, 2018, TNCLP announced that, in accordance with Section 17.1 of the TNCLP Partnership Agreement, TNGP elected to exercise the right, assigned to TNGP by TNCLP, to purchase all of the issued and outstanding common units representing limited partner interests in TNCLP not already owned by TNGP or its affiliates (the Public Units). TNGP will purchase the Public Units on April 2, 2018 for a cash purchase price of $84.033 per Public Unit. The purchase price was determined in accordance with Section 17.1 of the TNCLP Partnership Agreement as the average of the daily closing prices per common unit for the 20 consecutive trading days beginning with January 5, 2018 and ending with February 2, 2018. As of April 2, 2018, all rights of the holders of the Public Units will cease, except for the right to receive payment of the purchase price. Upon completion of the purchase on April 2, 2018, TNGP will own 100 percent of the Public Units and will be entitled to all of the benefits resulting from the Public Units. In addition, upon completion of the purchase, the common units representing limited partner interests in TNCLP will cease to be publicly traded or listed on the NYSE. We make quarterly distributions to holders of our general partner interest and limited partner interests based on Available Cash for the quarter as defined in the TNCLP Partnership Agreement. Available Cash is defined generally as all cash receipts less all cash disbursements, less certain reserves (including reserves for future operating and capital needs) established as the General Partner determines in its reasonable discretion to be necessary or appropriate. Changes in working capital affect Available Cash as increases in the amount of cash invested in working capital items (such as increases in receivables or inventory and decreases in accounts payable) reduce Available Cash, while declines in the amount of cash invested in working capital items increase Available Cash. During the years ended December 31, 2017 , 2016 and 2015 , we declared and paid partnership distributions of $124.6 million , $257.5 million and $294.8 million , respectively. We receive 99% of the Operating Partnership's Available Cash (as defined in the Operating Partnership's agreement of limited partnership) and 1% of the Operating Partnership's Available Cash is distributed by the Operating Partnership to the General Partner and its affiliate, TLPH. Distributions recognized by the Operating Partnership with respect to the General Partner and TLPH were $1.2 million , $2.6 million and $2.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Pursuant to the TNCLP Partnership Agreement, distributions of our Available Cash are made 99.975% to common and Class B common unitholders and 0.025% to the General Partner except that the General Partner is entitled, as an incentive, to a larger percentage of our distribution of Available Cash to the extent that cumulative distributions of Available Cash exceed specified target levels above the Minimum Quarterly Distributions (MQD) of $0.605 per unit. The General Partner has assigned its right to receive such incentive distributions to an affiliate of the General Partner. On February 7, 2018 , we announced a cash distribution of $2.03 per common unit, payable on February 28, 2018 to holders of record as of February 16, 2018 . As a result of TNGP’s exercise of the right to purchase the Public Units, there will be no further cash distributions on the common units after the distribution payable February 28, 2018. In the fourth quarter of 2017 , we exceeded the cumulative MQD amounts and will distribute Available Cash as summarized in the following table: Quarterly Income and Distribution Allocation Target Limit (per unit) Target Increment (per unit) Distribution Threshold (in millions) (1) Common Units Class B Common Units General Partner (2) Total Minimum Quarterly Distributions $ 0.605 $ 0.605 $ 11.3 98.990 % 0.985 % 0.025 % 100 % First Target 0.715 0.110 13.4 98.990 % 0.985 % 0.025 % 100 % Second Target 0.825 0.110 15.4 85.859 % 0.985 % 13.156 % 100 % Third Target 1.045 0.220 19.5 75.758 % 0.985 % 23.257 % 100 % Final Target and Beyond >1.045 — > 19.5 50.505 % 0.985 % 48.510 % 100 % _______________________________________________________________________________ (1) The Distribution Threshold represents the cumulative amount of Available Cash necessary to distribute the Target Limit per unit, as shown in the table above, to all unitholders and the General Partner based on the number of units outstanding as of December 31, 2017 . (2) Reflects Minimum Quarterly Distributions and incentive distributions to the General Partner. The General Partner has assigned its right to incentive distributions to an affiliate of the General Partner. We paid distributions of $5.15 , $8.74 and $9.75 per common unit during 2017 , 2016 and 2015 , respectively. We also paid distributions of $6.61 , $13.64 and $15.61 per Class B common unit during 2017 , 2016 and 2015 , respectively. The quarterly cash distributions to the unitholders and the General Partner declared to date in 2018 and during 2017 and 2016 are as follows: Distribution Common Units Class B Common Units General Partner Total Distributions Declared Declared in Related to Total Per unit Total Per unit Total (in millions, except per unit amounts) First Quarter 2018 Fourth Quarter 2017 $ 37.6 $ 2.03 $ 0.6 $ 3.10 $ 20.4 $ 58.6 First Quarter 2017 Fourth Quarter 2016 $ 22.6 $ 1.22 $ 0.3 $ 1.52 $ 5.7 $ 28.6 Second Quarter 2017 First Quarter 2017 17.9 0.97 0.2 1.04 1.4 19.5 Third Quarter 2017 Second Quarter 2017 29.6 1.60 0.4 2.26 12.7 42.7 Fourth Quarter 2017 Third Quarter 2017 25.2 1.36 0.3 1.79 8.3 33.8 First Quarter 2016 Fourth Quarter 2015 $ 53.3 $ 2.88 $ 0.9 $ 4.78 $ 36.0 $ 90.2 Second Quarter 2016 First Quarter 2016 28.0 1.51 0.4 2.09 11.1 39.5 Third Quarter 2016 Second Quarter 2016 47.7 2.58 0.7 4.17 30.4 78.8 Fourth Quarter 2016 Third Quarter 2016 32.7 1.77 0.5 2.60 15.8 49.0

Net Earnings per Common Unit

Net Earnings per Common Unit	12 Months Ended
	Dec. 31, 2017
Earnings Per Unit [Abstract]
Net Earnings per Common Unit	Net Earnings per Common Unit Net income and net losses are allocated to the common units, Class B common units and the general partner interest in accordance with the provisions of the TNCLP Partnership Agreement. In general, the TNCLP Partnership Agreement provides that if the Partnership has a net profit for a year, net income (including any undistributed net earnings) will be allocated among the General Partner and limited partners in the same proportion that Available Cash for such year was declared among the General Partner and the limited partners. If the Partnership has a net loss for a year, the loss will be allocated among the General Partner and limited partners in the same proportion as any net income was allocated to such partners in prior years (beginning with the first year in which net income was allocated to the partners). Net earnings per common unit are calculated using the two-class method and are based on the weighted-average number of common units outstanding during the period. The following table provides a calculation for net earnings per common unit for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in millions, except per unit amounts) Basic earnings per common unit: Net earnings $ 153.9 $ 209.3 $ 306.9 Less distributions declared to: Common units 110.3 130.9 187.4 Class B common units 1.5 1.9 3.1 General partner interest 42.8 63.1 118.4 (Distributions in excess of earnings) undistributed earnings $ (0.7 ) $ 13.4 $ (2.0 ) Allocation percentage for undistributed earnings or distributions in excess of earnings (1) : Common units 71.33 % 66.82 % 60.67 % Class B common units 0.97 % 0.97 % 0.97 % General partner interest 27.70 % 32.21 % 38.36 % Allocation of (distributions in excess of earnings) undistributed earnings to: Common units $ (0.5 ) $ 9.0 $ (1.2 ) Class B common units — 0.1 (0.1 ) General partner interest (0.2 ) 4.3 (0.7 ) Total (distributions in excess of earnings) undistributed earnings $ (0.7 ) $ 13.4 $ (2.0 ) Net earnings allocable to General Partner (2) $ 42.6 $ 67.4 $ 117.7 Net earnings allocable to Class B common units $ 1.5 $ 2.0 $ 3.0 Net earnings allocable to common units $ 109.8 $ 139.9 $ 186.2 Weighted-average common units outstanding 18.5 18.5 18.5 Net earnings per common unit $ 5.93 $ 7.56 $ 10.06 (1) In accordance with the TNCLP Partnership Agreement, undistributed earnings or distributions in excess of earnings are allocated in the same percentage that Available Cash for such period was declared among the General Partner (including with respect to the embedded incentive distribution rights) and limited partners. (2) Net earnings allocable to the General Partner include net earnings allocated to the General Partner and TLPH from the Operating Partnership of $1.5 million , $2.1 million and $3.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. There were no dilutive TNCLP units outstanding for the years ended December 31, 2017 , 2016 and 2015 and therefore basic and diluted net earnings per common unit are the same.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consisted of the following: December 31, 2017 2016 (in millions) Finished goods $ 3.5 $ 6.8 Raw materials, spare parts and supplies 1.8 1.8 Total $ 5.3 $ 8.6

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments Derivative financial instruments are executed on our behalf by an affiliate of the General Partner to reduce our exposure to changes in commodity prices for natural gas. Natural gas is the largest and most volatile component of the manufacturing cost for nitrogen-based fertilizers. The derivatives that we use are primarily natural gas fixed price swaps and options traded in the over-the-counter (OTC) markets. The derivative contract prices are based on NYMEX future prices based on physical delivery of natural gas at the Henry Hub in Louisiana, the most common and financially liquid location of reference for derivative financial instruments related to natural gas. However, we purchase natural gas for our manufacturing facility from suppliers whose prices are based primarily on the ONEOK index (based on physical delivery of natural gas in Oklahoma, rather than at the Henry Hub). This creates a location basis differential between the derivative contract price and the price we pay for physical delivery of natural gas. Accordingly, the prices underlying the derivative financial instruments we use may not exactly match the prices of natural gas we purchase and consume. We enter into natural gas derivative contracts with respect to gas to be consumed by us in the future, and settlements of those derivative contracts are scheduled to coincide with our anticipated purchases of natural gas used to manufacture nitrogen products during those future periods. We use natural gas derivatives as an economic hedge of gas price risk, but without the application of hedge accounting. The gross fair values of derivatives in our consolidated balance sheets are shown below. All balance sheet amounts from derivatives arise from natural gas derivatives that are not designated as hedging instruments. For additional information on derivative fair values, see Note 8—Fair Value Measurements . December 31, 2017 2016 (in millions) Derivative Assets Unrealized gains in other current assets $ — $ 7.9 Unrealized gains in other assets — 1.1 Total derivative assets — 9.0 Derivative Liabilities Unrealized losses in other current liabilities (3.2 ) — Unrealized losses in other liabilities — (1.6 ) Total derivative liabilities (3.2 ) (1.6 ) Net derivative (liabilities) assets $ (3.2 ) $ 7.4 The effect of derivatives in our consolidated statements of operations is shown below. All amounts arise from natural gas derivatives that are not designated as hedging instruments and are recorded in cost of goods sold. Year ended December 31, 2017 2016 2015 (in millions) Unrealized net mark-to-market (losses) gains $ (10.6 ) $ 35.3 $ (23.1 ) Realized net losses (3.0 ) (16.7 ) (10.6 ) Net derivative (losses) gains $ (13.6 ) $ 18.6 $ (33.7 ) As of December 31, 2017 and 2016 , we had open natural gas derivative contracts for 8.4 million MMBtus (millions of British thermal units) of natural gas and 29.4 million MMBtus of natural gas, respectively. The derivative portfolio at December 31, 2017 includes natural gas derivatives that economically hedge a portion of anticipated natural gas purchases through December 2018. For the year ended December 31, 2017 , we used derivatives to cover approximately 48% of our natural gas consumption. The counterparties to our derivative contracts are multinational commercial banks, other major financial institutions and large energy companies. The derivatives are executed with several counterparties, generally under International Swaps and Derivatives Association (ISDA) agreements. The ISDA agreements are master netting arrangements commonly used for OTC derivatives that mitigate exposure to counterparty credit risk, in part, by creating contractual rights of netting and setoff, the specifics of which vary from agreement to agreement. These rights are described further below: • Settlement netting generally allows the parties to net, into a single net payable or receivable, ordinary settlement obligations arising under the ISDA agreement on the same day, in the same currency, for the same types of derivative instruments, and through the same pairing of offices. • Close-out netting rights are provided in the event of a default or other termination event (as defined in the ISDA agreements), including bankruptcy. Depending on the cause of early termination, the non-defaulting party may elect to terminate all or some transactions outstanding under the ISDA agreement. The values of all terminated transactions and certain other payments under the ISDA agreement are netted, resulting in a single net close-out amount payable to or by the non-defaulting party. Termination values may be determined using a mark-to-market approach or based on a party's good faith estimate of its loss. If the final net close-out amount is payable by the non-defaulting party, that party's obligation to make the payment may be conditioned on factors such as the termination of all derivative transactions between the parties or payment in full of all of the defaulting party's obligations to the non-defaulting party, in each case regardless of whether arising under the ISDA agreement or otherwise. • Setoff rights are provided by certain of the ISDA agreements and generally allow a non-defaulting party to elect to set off, against the final net close-out payment, other matured and contingent amounts payable between the parties under the ISDA agreement or otherwise. Typically, these setoff rights arise upon the early termination of all transactions outstanding under an ISDA agreement following a default or specified termination event. Most of the ISDA agreements contain credit-risk-related contingent features such as cross-default provisions and credit support thresholds that are dependent upon the credit ratings of the General Partner affiliate. In the event of certain defaults or a credit ratings downgrade of the General Partner affiliate, the counterparty may request early termination and net settlement of certain derivative trades or may require the General Partner affiliate to collateralize derivatives in a net liability position. The General Partner affiliate’s revolving credit agreement, at any time when it is secured, provides a cross collateral feature for those derivatives that are with counterparties that are party to, or affiliates of parties to, the revolving credit agreement so that no separate collateral would be required for those counterparties in connection with such derivatives. In the event the General Partner affiliate's revolving credit agreement becomes unsecured, the General Partner affiliate could be required to post separate collateral in connection with such derivatives. As of December 31, 2017 and 2016 , the aggregate fair value of the derivative instruments with credit-risk-related contingent features in a net liability position was $3.2 million and $1.6 million , respectively, which also approximates the fair value of the maximum amount of assets needed to settle the obligations if the credit-risk-related contingent features were triggered and the General Partner affiliate was unable to post collateral at the reporting dates. As of December 31, 2017 and 2016 , we and the General Partner affiliate had no cash collateral on deposit for derivative contracts assigned to us. The credit support documents executed in connection with certain ISDA agreements generally provide the General Partner affiliate and the counterparties the right to set off collateral against amounts owing under the ISDA agreements upon the occurrence of a default or a specified termination event. The following table presents amounts relevant to offsetting of our derivative assets and liabilities as of December 31, 2017 and 2016 : Gross amounts not offset in consolidated balance sheets Gross and net amounts presented in consolidated balance sheets (1) Financial instruments Cash collateral received (pledged) Net amount (in millions) December 31, 2017 Total derivative assets $ — $ — $ — $ — Total derivative liabilities (3.2 ) — — (3.2 ) Net derivative liabilities $ (3.2 ) $ — $ — $ (3.2 ) December 31, 2016 Total derivative assets $ 9.0 $ 1.6 $ — $ 7.4 Total derivative liabilities (1.6 ) (1.6 ) — — Net derivative assets $ 7.4 $ — $ — $ 7.4 _______________________________________________________________________________ (1) We report the fair values of our derivative assets and liabilities on a gross basis in our consolidated balance sheets. As a result, the gross amounts recognized and net amounts presented herein are the same.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table presents assets and liabilities included in our consolidated balance sheets that are recognized at fair value on a recurring basis, and indicates the fair value hierarchy utilized to determine such fair value as of December 31, 2017 and 2016 : Balances as of December 31, 2017 Total Quoted Market Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in millions) Cash equivalents $ 80.5 $ 80.5 $ — $ — Total assets at fair value $ 80.5 $ 80.5 $ — $ — Unrealized losses on natural gas derivatives $ (3.2 ) $ — $ (3.2 ) $ — Total liabilities at fair value $ (3.2 ) $ — $ (3.2 ) $ — Balances as of December 31, 2016 Total Quoted Market Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in millions) Cash equivalents $ 32.0 $ 32.0 $ — $ — Unrealized gains on natural gas derivatives 9.0 — 9.0 — Total assets at fair value $ 41.0 $ 32.0 $ 9.0 $ — Unrealized losses on natural gas derivatives $ (1.6 ) $ — $ (1.6 ) $ — Total liabilities at fair value $ (1.6 ) $ — $ (1.6 ) $ — Cash Equivalents As of December 31, 2017 and 2016 , our cash equivalents consisted primarily of money market mutual funds that invest in U.S. treasuries and direct investments in U.S. treasuries with original maturities of three months or less. Natural Gas Derivatives The derivative instruments that we use are primarily natural gas fixed price swaps and options traded in the OTC markets with multinational commercial banks, other major financial institutions and large energy companies. The derivatives are traded in months forward and settlements are scheduled to coincide with anticipated gas purchases during those future periods. These contracts settle using NYMEX futures prices and accordingly, to determine the fair value of these instruments, we use quoted market prices from NYMEX and standard pricing models with inputs derived from or corroborated by observable market data such as forward curves supplied by an industry-recognized unrelated third party. See Note 7—Derivative Financial Instruments for additional information. Assets Measured at Fair Value on a Nonrecurring Basis We also have assets that may be measured at fair value on a nonrecurring basis; that is, the assets are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances, such as when there is evidence of impairment. These include long-lived assets that may be written down to fair value as a result of impairment. We determined that these fair value measurements would rely primarily on Partnership-specific inputs and the Partnership's assumptions about the use of the assets. Since certain of the assumptions would involve inputs that are not observable, these fair values would reside within Level 3 of the fair value hierarchy.

Property, Plant and Equipment,

Property, Plant and Equipment, Net	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Net	Property, Plant and Equipment—Net Property, plant and equipment—net consisted of the following: December 31, 2017 2016 (in millions) Land $ 1.4 $ 1.4 Buildings and improvements 16.9 16.7 Machinery and equipment 568.3 562.3 Construction in progress 41.1 21.9 Property, plant and equipment 627.7 602.3 Less: Accumulated depreciation and amortization 337.5 301.0 Property, plant and equipment—net $ 290.2 $ 301.3 Property, plant and equipment used to produce nitrogen fertilizer products are subject to the Services and Offtake Agreement with an affiliate of the General Partner, which is accounted for as an operating lease. See Note 10—Related Party Transactions for additional information. Additions to property, plant and equipment included in our consolidated statements of cash flows represents cash outflows for capital expenditures; therefore, it does not include the net increase (decrease) in amounts accrued for capital expenditures, which were $0.6 million , $1.8 million and $(2.2) million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Losses on the disposal of certain machinery and equipment were zero , $0.1 million and $2.0 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, and are included in other general and administrative expenses in our consolidated statements of operations. Plant turnarounds —Scheduled inspections, replacements and overhauls of machinery and equipment at our continuous process manufacturing facility are referred to as plant turnarounds. The expenditures related to turnarounds are capitalized in property, plant and equipment when incurred. The following is a summary of capitalized plant turnaround costs: Year ended December 31, 2017 2016 2015 (in millions) Net capitalized turnaround costs: Beginning balance $ 26.6 $ 37.8 $ 16.7 Additions 2.3 4.9 33.6 Depreciation (14.2 ) (16.1 ) (12.5 ) Ending balance $ 14.7 $ 26.6 $ 37.8 Scheduled replacements and overhauls of machinery and equipment include the dismantling, repair or replacement and installation of various components including piping, valves, motors, turbines, pumps, compressors, heat exchangers and the replacement of catalyst when a full plant shutdown occurs. Scheduled inspections are also conducted during full plant shutdowns, including required safety inspections which entail the disassembly of various components such as steam boilers, pressure vessels and other equipment requiring safety certifications. Internal employee costs and overhead are not considered turnaround costs and are not capitalized.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions TNCLP and TNGP have no employees. We have entered into several agreements with subsidiaries of CF Industries relating to the operation of our business and the sale of the fertilizer products produced at our Verdigris facility. We believe that each of these agreements is on terms that are fair and reasonable to us. Product Sales Pursuant to the Services and Offtake Agreement, which is accounted for as an operating lease, the Partnership sells all of its fertilizer products to affiliates of the General Partner at prices based on market prices for the Partnership's nitrogen fertilizer products. Also, pursuant to the Services and Offtake Agreement, selling prices are determined monthly and are equal to the volume weighted average net invoice price for third party sales (that is, sales by the affiliates of the General Partner to their customers) of product during each month. These selling prices are reduced by any freight or other transportation charges and incentives paid by the affiliates of the General Partner. Title and risk of loss transfer to affiliates of the General Partner as the product is shipped from the plant gate. The Services and Offtake Agreement was effective initially for a one-year term and is extended automatically for successive one -year terms unless terminated by one of the parties prior to renewal. The Services and Offtake Agreement is accounted for as an operating lease comprised entirely of variable lease payments associated with the sale of our products. Directly Incurred Charges Since we have no employees, we rely on employees from an affiliate of the General Partner to operate our Verdigris facility. As a result, the payroll, payroll-related expenses and benefit costs, such as health insurance and pension costs, are incurred by an affiliate of the General Partner and directly charged to us. Payroll, payroll-related expenses and other employee-related benefit costs directly charged to us were $27.9 million for each of the years ended December 31, 2017 , 2016 and 2015 . We report these expenses as services provided by affiliates of the General Partner in cost of goods sold in our consolidated statements of operations. Allocated Charges CF Industries, together with its affiliates, also provides certain services to us under the Services and Offtake Agreement. These services include production planning, manufacturing management, logistics, procurement, accounting, legal, risk management, investor relations and other general and administrative functions. Allocated expenses charged to us in each of the years ended December 31, 2017 , 2016 and 2015 were $15.9 million , $15.7 million and $15.7 million , respectively. We report these expenses as selling, general and administrative services provided by affiliates of the General Partner in our consolidated statements of operations. Amounts Due to/from Affiliates of the General Partner We receive cash and make expenditures directly from our cash accounts. Because we sell our products to and receive labor and other services from affiliates of the General Partner, the affiliates of the General Partner continue to be both debtors and creditors to us. As of December 31, 2017 and 2016 , we had a net balance due from (to) affiliates of the General Partner of $12.9 million and $(0.1) million , respectively. Spare Parts Sharing Agreement Affiliates of CF Industries own and operate nitrogen fertilizer complexes that utilize some equipment that is similar to equipment at our Verdigris nitrogen complex. Each of the various manufacturing complexes maintains spare parts for use in its facilities. In the event that an unplanned need arises and to help minimize manufacturing downtime, we have entered into a spare parts sharing agreement with affiliates of CF Industries that permits spare parts to be shared among the manufacturing complexes from time to time. Parts that are borrowed from another complex under the agreement are either refurbished and returned to the lender or replaced. Other Leases We entered into an amended and restated lease with an affiliate of the General Partner under which the ammonia assets in our terminal in Blair, Nebraska are leased by the affiliate. The lease is effective for a five -year term ending on December 31, 2018, and the affiliate of the General Partner has options to renew for three additional five -year terms. The quarterly lease payment is $100,000 , subject to an annual inflation adjustment, and additional rent will be paid equal to all costs, expenses, and obligations incurred by the affiliate of the General Partner related to the use, occupancy and operation of the terminal. We also have leased certain of our rail cars to an affiliate of the General Partner for quarterly rental payments of $3,600 per car. This lease was effective initially for a one -year term and is extended automatically for successive one -year terms unless terminated by either party thereto prior to renewal. In each of the years ended December 31, 2017 , 2016 and 2015 , we recognized rental income of $0.6 million . We report this income as other income from an affiliate of the General Partner in our consolidated statements of operations.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations Asset retirement obligations (AROs) are legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development or normal operation of such assets. AROs are initially recognized as incurred when sufficient information exists to estimate fair value. We have unrecorded AROs at our Verdigris facility that are conditional upon cessation of operations. These AROs include certain decommissioning and pond closure activities, and the removal and disposal of certain chemicals, waste materials, structures, equipment, vessels, piping and storage tanks. The most recent estimate of the aggregate cost of these AROs expressed in 2017 dollars is $4.0 million . We have not recorded a liability for these conditional AROs as of December 31, 2017 because we do not believe there is currently a reasonable basis for estimating a date or range of dates of cessation of operations at this facility, which is necessary in order to estimate fair value. In reaching this conclusion, we considered the historical performance of the facility and have taken into account factors such as planned maintenance, asset replacements and upgrades of plant and equipment, which if conducted as in the past, can extend the physical lives of the facility indefinitely, as well as the possibility of changes in technology, risk of obsolescence and availability of raw materials in arriving at our conclusion.

Commitments

Commitments	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments	Commitments The Operating Partnership is committed to various non-cancelable operating leases for land, buildings and equipment. Total minimum rental payments for operating leases are insignificant for 2018 and all subsequent years. Rent expense under non-cancelable operating leases for the years ended December 31, 2017 , 2016 and 2015 was insignificant.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	Quarterly Financial Data (Unaudited) Summarized quarterly financial data are as follows: First Quarter Second Quarter Third Quarter Fourth Quarter Full Year (in millions, except per unit amounts) 2017 Net sales $ 119.0 $ 96.1 $ 84.6 $ 97.5 $ 397.2 Gross margin 46.6 43.5 27.2 39.4 156.7 Net earnings (1) 42.2 39.5 22.8 49.4 153.9 Net earnings per Common Unit (1) (2) 2.10 1.48 0.92 1.44 5.93 2016 Net sales $ 108.0 $ 126.7 $ 90.2 $ 93.4 $ 418.3 Gross margin 43.1 102.7 32.8 48.2 226.8 Net earnings 37.7 98.7 28.8 44.1 209.3 Net earnings per Common Unit (2) 1.44 3.22 1.04 1.85 7.56 (1) The fourth quarter of 2017 includes a gain of $14.3 million for the sale of our 50% joint venture interest in Oklahoma CO2 Partnership (OKCO2). See Note 14—Sale of Equity Method Investment . (2) The sum of the four quarters is not necessarily the same as the total for the year.

Sale of Equity Method Investmen

Sale of Equity Method Investment (Notes)	12 Months Ended
	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Equity Method Investments and Joint Ventures Disclosure [Text Block]	Sale of Equity Method Investment On October 2, 2017, we sold our 50% interest in OKCO2, a joint venture that owns a carbon dioxide liquefaction and purification facility, to the joint venture partner. Prior to the sale, we had accounted for this interest as an equity method investment. We received proceeds of $16.3 million for the sale and recorded a gain of $14.3 million after the completion of certain customary closing and working capital adjustments in the fourth quarter of 2017. The proceeds were included in the determination of Available Cash for the fourth quarter of 2017.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2017
Subsequent Event [Line Items]
Subsequent Events [Text Block]	Subsequent Event On February 7, 2018, TNCLP announced that, in accordance with Section 17.1 of the TNCLP Partnership Agreement, TNGP elected to exercise the right, assigned to TNGP by TNCLP, to purchase all of the issued and outstanding common units representing limited partner interests in TNCLP not already owned by TNGP or its affiliates (the Public Units). TNGP will purchase the Public Units on April 2, 2018 for a cash purchase price of $84.033 per Public Unit. The purchase price was determined in accordance with Section 17.1 of the TNCLP Partnership Agreement as the average of the daily closing prices per common unit for the 20 consecutive trading days beginning with January 5, 2018 and ending with February 2, 2018. As of April 2, 2018, all rights of the holders of the Public Units will cease, except for the right to receive payment of the purchase price. Upon completion of the purchase on April 2, 2018, TNGP will own 100 percent of the Public Units and will be entitled to all of the benefits resulting from the Public Units. As a result of TNGP’s exercise of the right to purchase the Public Units, there will be no further cash distributions on the common units after the distribution payable February 28, 2018. In addition, upon completion of the purchase, the common units representing limited partner interests in TNCLP will cease to be publicly traded or listed on the NYSE.

Summary of Significant Accoun22

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Consolidation	Consolidation The consolidated financial statements of TNCLP and the accompanying notes include the accounts of the Partnership. All intercompany transactions and balances have been eliminated. Income is allocated to the General Partner and the limited partners of TNCLP (Limited Partners) in accordance with the provisions of the TNCLP Partnership Agreement that provides for allocations of income between the Limited Partners and the General Partner in the same proportion as cash distributions related to such year. The 0.975% limited partner interest and the 0.025% general partner interest in the Operating Partnership held by TLPH and the General Partner, respectively, are included in the line labeled General Partner’s interest in the consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses for the periods presented. Actual results could differ from these estimates. Significant estimates and assumptions are used for, but are not limited to, the net realizable value of inventories, environmental remediation liabilities, environmental and litigation contingencies, useful lives of property, plant and equipment, the assumptions used in the evaluation of potential impairments of property, plant and equipment and the allowance for doubtful accounts receivable.
Revenue Recognition	Revenue Recognition The primary products we sell are ammonia and UAN. Sales are made in accordance with the Amendment to the General and Administrative Services and Product Offtake Agreement (the Services and Offtake Agreement) we have with an affiliate of the General Partner under which affiliates of the General Partner purchase our products. We recognize revenue as products are shipped from the plant gate when title and risk of loss transfer to affiliates of the General Partner. The Services and Offtake Agreement is accounted for as an operating lease comprised entirely of variable lease payments associated with the sale of our products. The Services and Offtake Agreement is described in Note 10—Related Party Transactions .
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include highly liquid investments that are readily convertible to known amounts of cash with original maturities of three months or less. The carrying value of cash and cash equivalents approximates fair value.
Due to/from Affiliates of General Partner	Due to/from Affiliates of the General Partner We receive cash and make expenditures directly from our cash accounts. Because we sell our products to and receive labor and other services from affiliates of the General Partner, the affiliates of the General Partner continue to be both debtors and creditors to us.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at face amounts less an allowance for doubtful accounts. The allowance is an estimate based on historical collection experience, current economic and market conditions, and a review of the current status of each customer's trade accounts receivable. A receivable is past due if payments have not been received within the agreed upon invoice terms. Account balances are charged-off against the allowance when management determines that it is probable the receivable will not be recovered.
Inventories, net	Inventories Inventories are reported at the lower of cost and net realizable value and are determined on a first-in, first-out (FIFO) and average cost basis. Inventories include the cost of materials, production labor and production overhead. Net realizable value is reviewed quarterly. Fixed production costs related to idle capacity are not included in the cost of inventories but are charged directly to cost of sales. On January 1, 2017, we adopted Accounting Standards Update (ASU) No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory, as discussed in Note 3—New Accounting Standards .
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost and are subject to the Services and Offtake Agreement, which is accounted for as an operating lease, as described in Note 10—Related Party Transactions . Depreciation and amortization are computed using the straight-line method over the estimated useful life of the property, plant and equipment. Useful lives for property, plant, and equipment range from 10 to 40 years for buildings and 3 to 30 years for machinery and equipment. We periodically review these useful lives and change the estimates to reflect the results of those reviews. Scheduled inspections, replacements and overhauls of machinery and equipment at our continuous process manufacturing facility are referred to as plant turnarounds. Plant turnarounds are accounted for under the deferral method, as opposed to the direct expense or built-in overhaul methods. Under the deferral method, expenditures related to turnarounds are capitalized when incurred and amortized to production costs on a straight-line basis over the period benefited, which is until the next scheduled turnaround in up to 5 years . If the direct expense method were used, all turnaround costs would be expensed as incurred. Internal employee costs and overhead amounts are not considered turnaround costs and are not capitalized. Turnaround costs are classified as investing activities in our consolidated statements of cash flows. For additional information, see Note 9—Property, Plant and Equipment—Net .
Recoverability of Long-Lived Assets	Recoverability of Long-Lived Assets We review property, plant and equipment and other long-lived assets in order to assess recoverability based on expected future undiscounted cash flows whenever events or circumstances indicate that the carrying value may not be recoverable. If the sum of the expected future net cash flows is less than the carrying value, an impairment loss is recognized. The impairment loss is measured as the amount by which the carrying value exceeds the fair value of the asset.
Lessee, Leases	Other Leases Leases are classified as either operating leases or capital leases. Assets acquired under capital leases are depreciated on the same basis as property, plant and equipment. We currently do not have any capital leases. Rental payments, including rent holidays, leasehold incentives, and scheduled rent increases, if any, are expensed on a straight-line basis over the lease term.
Lessor, Leases	Other Leases Leases are classified as either operating leases or capital leases. Assets acquired under capital leases are depreciated on the same basis as property, plant and equipment. We currently do not have any capital leases. Rental payments, including rent holidays, leasehold incentives, and scheduled rent increases, if any, are expensed on a straight-line basis over the lease term.
Income Taxes	Income Taxes As a partnership, we are not subject to income taxes. For additional information, see Note 1—Background and Basis of Presentation . The income tax liability of the individual partners is not reflected in our consolidated financial statements.
Derivative Financial Instruments	Derivative Financial Instruments Natural gas is the principal raw material used to produce nitrogen fertilizers. We use natural gas both as a chemical feedstock and as a fuel to produce ammonia and UAN. We manage the risk of changes in natural gas prices primarily through the use of derivative financial instruments. The derivative instruments that we use are primarily natural gas fixed price swaps and options traded in the over-the-counter markets. These derivatives reference NYMEX futures contract prices, which represent the basis for fair value at any given time. The derivatives are traded in months forward and settlements are scheduled to coincide with anticipated gas purchases during those future periods. We do not use derivatives for trading purposes and are not a party to any leveraged derivatives. We have elected to not apply hedge accounting to our derivatives; as a result, changes in the fair value of the derivatives are recorded in cost of goods sold in our consolidated statements of operations. Derivatives are recognized in our consolidated balance sheets at fair value. Cash flows related to natural gas derivatives are reported as operating activities in our consolidated statements of cash flows. For additional information, see Note 7—Derivative Financial Instruments .
Asset Retirement Obligations	Asset Retirement Obligations Asset retirement obligations (AROs) are legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development or normal operation of such assets. AROs are initially recognized as liabilities as incurred when sufficient information exists to estimate fair value. When initially recognized, the fair value based on discounted future cash flows is recorded both as a liability and an increase in the carrying amount of the related long-lived asset. In subsequent periods, depreciation of the asset and accretion of the liability are recorded. For additional information on AROs, see Note 11—Asset Retirement Obligations .
Environmental	Environmental Environmental expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations are expensed. Expenditures that increase the capacity or extend the useful life of an asset, improve the safety or efficiency of the operations, or mitigate or prevent future environmental contamination are capitalized. Liabilities are recorded when it is probable that a liability has been incurred, the costs can be reasonably estimated, and the liability would not be discounted.
Litigation	Litigation From time to time, the Partnership is subject to ordinary, routine legal proceedings related to the usual conduct of its business. From time to time, the Partnership also is involved in legal proceedings regarding public utility and transportation rates, environmental matters, taxes and permits relating to the operations of its plant and facilities. Accruals for such contingencies are recorded to the extent management concludes their occurrence is probable and the financial impact of an adverse outcome is reasonably estimable. Disclosure for specific legal contingencies is provided if the likelihood of occurrence is at least reasonably possible and the exposure is considered material to the consolidated financial statements. In making determinations of likely outcomes of litigation matters, many factors are considered. These factors include, but are not limited to, past history, scientific and other evidence, and the specifics and status of each matter. If the assessment of various factors changes, the estimates may change. Predicting the outcome of claims and litigation, and estimating related costs and exposure involves substantial uncertainties that could cause actual costs to vary materially from estimates and accruals. Legal fees are expensed as incurred and are included in selling, general, and administrative services provided by affiliates of the General Partner in our consolidated statements of operations.

Agreement of Limited Partners23

Agreement of Limited Partnership (Tables)	12 Months Ended
	Dec. 31, 2017
Distributions Made to Members or Limited Partners [Abstract]
Summary of available cash distribution	In the fourth quarter of 2017 , we exceeded the cumulative MQD amounts and will distribute Available Cash as summarized in the following table: Quarterly Income and Distribution Allocation Target Limit (per unit) Target Increment (per unit) Distribution Threshold (in millions) (1) Common Units Class B Common Units General Partner (2) Total Minimum Quarterly Distributions $ 0.605 $ 0.605 $ 11.3 98.990 % 0.985 % 0.025 % 100 % First Target 0.715 0.110 13.4 98.990 % 0.985 % 0.025 % 100 % Second Target 0.825 0.110 15.4 85.859 % 0.985 % 13.156 % 100 % Third Target 1.045 0.220 19.5 75.758 % 0.985 % 23.257 % 100 % Final Target and Beyond >1.045 — > 19.5 50.505 % 0.985 % 48.510 % 100 %
Schedule of the quarterly cash distributions paid to the unitholders and the General Partner	The quarterly cash distributions to the unitholders and the General Partner declared to date in 2018 and during 2017 and 2016 are as follows: Distribution Common Units Class B Common Units General Partner Total Distributions Declared Declared in Related to Total Per unit Total Per unit Total (in millions, except per unit amounts) First Quarter 2018 Fourth Quarter 2017 $ 37.6 $ 2.03 $ 0.6 $ 3.10 $ 20.4 $ 58.6 First Quarter 2017 Fourth Quarter 2016 $ 22.6 $ 1.22 $ 0.3 $ 1.52 $ 5.7 $ 28.6 Second Quarter 2017 First Quarter 2017 17.9 0.97 0.2 1.04 1.4 19.5 Third Quarter 2017 Second Quarter 2017 29.6 1.60 0.4 2.26 12.7 42.7 Fourth Quarter 2017 Third Quarter 2017 25.2 1.36 0.3 1.79 8.3 33.8 First Quarter 2016 Fourth Quarter 2015 $ 53.3 $ 2.88 $ 0.9 $ 4.78 $ 36.0 $ 90.2 Second Quarter 2016 First Quarter 2016 28.0 1.51 0.4 2.09 11.1 39.5 Third Quarter 2016 Second Quarter 2016 47.7 2.58 0.7 4.17 30.4 78.8 Fourth Quarter 2016 Third Quarter 2016 32.7 1.77 0.5 2.60 15.8 49.0

Net Earnings per Common Unit (T

Net Earnings per Common Unit (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Unit [Abstract]
Schedule of calculation for net earnings per common unit	The following table provides a calculation for net earnings per common unit for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in millions, except per unit amounts) Basic earnings per common unit: Net earnings $ 153.9 $ 209.3 $ 306.9 Less distributions declared to: Common units 110.3 130.9 187.4 Class B common units 1.5 1.9 3.1 General partner interest 42.8 63.1 118.4 (Distributions in excess of earnings) undistributed earnings $ (0.7 ) $ 13.4 $ (2.0 ) Allocation percentage for undistributed earnings or distributions in excess of earnings (1) : Common units 71.33 % 66.82 % 60.67 % Class B common units 0.97 % 0.97 % 0.97 % General partner interest 27.70 % 32.21 % 38.36 % Allocation of (distributions in excess of earnings) undistributed earnings to: Common units $ (0.5 ) $ 9.0 $ (1.2 ) Class B common units — 0.1 (0.1 ) General partner interest (0.2 ) 4.3 (0.7 ) Total (distributions in excess of earnings) undistributed earnings $ (0.7 ) $ 13.4 $ (2.0 ) Net earnings allocable to General Partner (2) $ 42.6 $ 67.4 $ 117.7 Net earnings allocable to Class B common units $ 1.5 $ 2.0 $ 3.0 Net earnings allocable to common units $ 109.8 $ 139.9 $ 186.2 Weighted-average common units outstanding 18.5 18.5 18.5 Net earnings per common unit $ 5.93 $ 7.56 $ 10.06 (1) In accordance with the TNCLP Partnership Agreement, undistributed earnings or distributions in excess of earnings are allocated in the same percentage that Available Cash for such period was declared among the General Partner (including with respect to the embedded incentive distribution rights) and limited partners. (2) Net earnings allocable to the General Partner include net earnings allocated to the General Partner and TLPH from the Operating Partnership of $1.5 million , $2.1 million and $3.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Schedule of inventories	Inventories consisted of the following: December 31, 2017 2016 (in millions) Finished goods $ 3.5 $ 6.8 Raw materials, spare parts and supplies 1.8 1.8 Total $ 5.3 $ 8.6

Derivative Financial Instrume26

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of the gross fair values of derivatives on balance sheet	The gross fair values of derivatives in our consolidated balance sheets are shown below. All balance sheet amounts from derivatives arise from natural gas derivatives that are not designated as hedging instruments. For additional information on derivative fair values, see Note 8—Fair Value Measurements . December 31, 2017 2016 (in millions) Derivative Assets Unrealized gains in other current assets $ — $ 7.9 Unrealized gains in other assets — 1.1 Total derivative assets — 9.0 Derivative Liabilities Unrealized losses in other current liabilities (3.2 ) — Unrealized losses in other liabilities — (1.6 ) Total derivative liabilities (3.2 ) (1.6 ) Net derivative (liabilities) assets $ (3.2 ) $ 7.4
Schedule of effects of derivatives in consolidated statements of operations	The effect of derivatives in our consolidated statements of operations is shown below. All amounts arise from natural gas derivatives that are not designated as hedging instruments and are recorded in cost of goods sold. Year ended December 31, 2017 2016 2015 (in millions) Unrealized net mark-to-market (losses) gains $ (10.6 ) $ 35.3 $ (23.1 ) Realized net losses (3.0 ) (16.7 ) (10.6 ) Net derivative (losses) gains $ (13.6 ) $ 18.6 $ (33.7 )
Schedule of offsetting of derivative assets and liabilities	The following table presents amounts relevant to offsetting of our derivative assets and liabilities as of December 31, 2017 and 2016 : Gross amounts not offset in consolidated balance sheets Gross and net amounts presented in consolidated balance sheets (1) Financial instruments Cash collateral received (pledged) Net amount (in millions) December 31, 2017 Total derivative assets $ — $ — $ — $ — Total derivative liabilities (3.2 ) — — (3.2 ) Net derivative liabilities $ (3.2 ) $ — $ — $ (3.2 ) December 31, 2016 Total derivative assets $ 9.0 $ 1.6 $ — $ 7.4 Total derivative liabilities (1.6 ) (1.6 ) — — Net derivative assets $ 7.4 $ — $ — $ 7.4 _______________________________________________________________________________ (1) We report the fair values of our derivative assets and liabilities on a gross basis in our consolidated balance sheets. As a result, the gross amounts recognized and net amounts presented herein are the same.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of assets and liabilities that are recognized at fair value on a recurring basis	The following table presents assets and liabilities included in our consolidated balance sheets that are recognized at fair value on a recurring basis, and indicates the fair value hierarchy utilized to determine such fair value as of December 31, 2017 and 2016 : Balances as of December 31, 2017 Total Quoted Market Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in millions) Cash equivalents $ 80.5 $ 80.5 $ — $ — Total assets at fair value $ 80.5 $ 80.5 $ — $ — Unrealized losses on natural gas derivatives $ (3.2 ) $ — $ (3.2 ) $ — Total liabilities at fair value $ (3.2 ) $ — $ (3.2 ) $ — Balances as of December 31, 2016 Total Quoted Market Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) (in millions) Cash equivalents $ 32.0 $ 32.0 $ — $ — Unrealized gains on natural gas derivatives 9.0 — 9.0 — Total assets at fair value $ 41.0 $ 32.0 $ 9.0 $ — Unrealized losses on natural gas derivatives $ (1.6 ) $ — $ (1.6 ) $ — Total liabilities at fair value $ (1.6 ) $ — $ (1.6 ) $ —

Property, Plant and Equipment28

Property, Plant and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of property, plant and equipment, net	Property, plant and equipment—net consisted of the following: December 31, 2017 2016 (in millions) Land $ 1.4 $ 1.4 Buildings and improvements 16.9 16.7 Machinery and equipment 568.3 562.3 Construction in progress 41.1 21.9 Property, plant and equipment 627.7 602.3 Less: Accumulated depreciation and amortization 337.5 301.0 Property, plant and equipment—net $ 290.2 $ 301.3
Summary of plant turnaround activity	The following is a summary of capitalized plant turnaround costs: Year ended December 31, 2017 2016 2015 (in millions) Net capitalized turnaround costs: Beginning balance $ 26.6 $ 37.8 $ 16.7 Additions 2.3 4.9 33.6 Depreciation (14.2 ) (16.1 ) (12.5 ) Ending balance $ 14.7 $ 26.6 $ 37.8

Quarterly Financial Data (Una29

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Summary of quarterly financial data	Summarized quarterly financial data are as follows: First Quarter Second Quarter Third Quarter Fourth Quarter Full Year (in millions, except per unit amounts) 2017 Net sales $ 119.0 $ 96.1 $ 84.6 $ 97.5 $ 397.2 Gross margin 46.6 43.5 27.2 39.4 156.7 Net earnings (1) 42.2 39.5 22.8 49.4 153.9 Net earnings per Common Unit (1) (2) 2.10 1.48 0.92 1.44 5.93 2016 Net sales $ 108.0 $ 126.7 $ 90.2 $ 93.4 $ 418.3 Gross margin 43.1 102.7 32.8 48.2 226.8 Net earnings 37.7 98.7 28.8 44.1 209.3 Net earnings per Common Unit (2) 1.44 3.22 1.04 1.85 7.56 (1) The fourth quarter of 2017 includes a gain of $14.3 million for the sale of our 50% joint venture interest in Oklahoma CO2 Partnership (OKCO2). See Note 14—Sale of Equity Method Investment . (2) The sum of the four quarters is not necessarily the same as the total for the year.

Background and Basis of Prese30

Background and Basis of Presentation (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Common units and interest in the partnership
General Partners' Capital Account, Units Issued	4,720
Common
Common units and interest in the partnership
Common Units issued	18,501,576	18,501,576
Common Units outstanding	18,501,576	18,501,576
Class B Common Units
Common units and interest in the partnership
Common Units issued	184,072	184,072
Common Units outstanding	184,072	184,072
CF Industries Holdings Inc [Member] | Common
Common units and interest in the partnership
Common units owned through subsidiaries	13,889,014
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest	75.10%
Limited Partner [Member]
Common units and interest in the partnership
Ownership interest in the partnership (as a percent)	99.00%
General Partner's Interest
Common units and interest in the partnership
Ownership interest in the partnership (as a percent)	0.025%
Affiliate of General Partner | Limited Partner [Member] | Terra LP Holdings LLC [Member]
Common units and interest in the partnership
Ownership interest in the partnership (as a percent)	0.975%

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2017
Maximum
Property, Plant and Equipment
Turnaround period	5 years
Buildings | Minimum
Property, Plant and Equipment
Depreciable life	10 years
Buildings | Maximum
Property, Plant and Equipment
Depreciable life	40 years
Machinery and equipment | Minimum
Property, Plant and Equipment
Depreciable life	3 years
Machinery and equipment | Maximum
Property, Plant and Equipment
Depreciable life	30 years
Limited Partner [Member]
Property, Plant and Equipment
Ownership interest in the partnership (as a percent)	99.00%
General Partner's Interest
Property, Plant and Equipment
Ownership interest in the partnership (as a percent)	0.025%
Affiliate of General Partner | Terra LP Holdings LLC [Member] | Limited Partner [Member]
Property, Plant and Equipment
Ownership interest in the partnership (as a percent)	0.975%

Agreement of Limited Partners32

Agreement of Limited Partnership (Details)	Feb. 07, 2018$ / shares	Mar. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)$ / shares	Sep. 30, 2017USD ($)$ / shares	Jun. 30, 2017USD ($)$ / shares	Mar. 31, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)$ / shares	Sep. 30, 2016USD ($)$ / shares	Jun. 30, 2016USD ($)$ / shares	Mar. 31, 2016USD ($)$ / shares	Dec. 31, 2017USD ($)trading_day$ / shares$ / Unit	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares
Agreement of limited partnership
Declared and paid partnership distributions											$ 124,600,000	$ 257,500,000	$ 294,800,000
Available cash received from operating partnership (as a percent)											99.00%
Distribution Made to Limited and General Partners, Distributions Declared, Total			$ 33,800,000	$ 42,700,000	$ 19,500,000	$ 28,600,000	$ 49,000,000	$ 78,800,000	$ 39,500,000	$ 90,200,000
Number of average trading days' closing prices used to determine the purchase price of outstanding units of non-affiliates | trading_day											20
Minimum Quarterly Distributions
Agreement of limited partnership
Target Limit (per unit) | $ / Unit											0.605
Target Increment (per unit) | $ / Unit											0.605
Income and distribution allocation (as a percent)											100.00%
Minimum Quarterly Distributions | Maximum
Agreement of limited partnership
Incentive Distribution, Distribution											$ 11.3
First Target
Agreement of limited partnership
Target Limit (per unit) | $ / Unit											0.715
Target Increment (per unit) | $ / Unit											0.110
Income and distribution allocation (as a percent)											100.00%
First Target | Maximum
Agreement of limited partnership
Incentive Distribution, Distribution											$ 13.4
Second Target
Agreement of limited partnership
Target Limit (per unit) | $ / Unit											0.825
Target Increment (per unit) | $ / Unit											0.110
Income and distribution allocation (as a percent)											100.00%
Second Target | Maximum
Agreement of limited partnership
Incentive Distribution, Distribution											$ 15.4
Third Target
Agreement of limited partnership
Target Limit (per unit) | $ / Unit											1.045
Target Increment (per unit) | $ / Unit											0.220
Income and distribution allocation (as a percent)											100.00%
Third Target | Maximum
Agreement of limited partnership
Incentive Distribution, Distribution											$ 19.5
Final Target and Beyond
Agreement of limited partnership
Target Increment (per unit) | $ / Unit											0
Income and distribution allocation (as a percent)											100.00%
Final Target and Beyond | Minimum
Agreement of limited partnership
Target Limit (per unit) | $ / Unit											1.045
Incentive Distribution, Distribution											$ 19.5
Common and Class B Common Units
Agreement of limited partnership
Cash distribution made, excluding when cumulative distribution is specified, (as a percent)											99.975%
Common units
Agreement of limited partnership
Declared and paid partnership distributions			$ 25,200,000	$ 29,600,000	$ 17,900,000	$ 22,600,000	$ 32,700,000	$ 47,700,000	$ 28,000,000	$ 53,300,000
Cash distribution declared per common limited partnership unit (in dollars per unit) | $ / shares			$ 1.36	$ 1.60	$ 0.97	$ 1.22	$ 1.77	$ 2.58	$ 1.51	$ 2.88	$ 5.15	$ 8.74	$ 9.75
Common units | Minimum Quarterly Distributions
Agreement of limited partnership
Income and distribution allocation (as a percent)											98.99%
Common units | First Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											98.99%
Common units | Second Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											85.859%
Common units | Third Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											75.758%
Common units | Final Target and Beyond
Agreement of limited partnership
Income and distribution allocation (as a percent)											50.505%
Class B Common Units
Agreement of limited partnership
Declared and paid partnership distributions			$ 300,000	$ 400,000	$ 200,000	$ 300,000	$ 500,000	$ 700,000	$ 400,000	$ 900,000
Cash distribution declared per common limited partnership unit (in dollars per unit) | $ / shares			$ 1.79	$ 2.26	$ 1.04	$ 1.52	$ 2.60	$ 4.17	$ 2.09	$ 4.78	$ 6.61	$ 13.64	$ 15.61
Class B Common Units | Minimum Quarterly Distributions
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.985%
Class B Common Units | First Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.985%
Class B Common Units | Second Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.985%
Class B Common Units | Third Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.985%
Class B Common Units | Final Target and Beyond
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.985%
General Partner's Interest
Agreement of limited partnership
Declared and paid partnership distributions			$ 8,300,000	$ 12,700,000	$ 1,400,000	$ 5,700,000	$ 15,800,000	$ 30,400,000	$ 11,100,000	$ 36,000,000
Available cash distributed from operating partnership to General Partner (as a percent)											1.00%
General Partner Distributions											$ (1,200,000)	$ (2,600,000)	$ (2,900,000)
Cash distribution made, excluding when cumulative distribution is specified, (as a percent)											0.025%
Percentage of outstanding units owned by the General Partner and its affiliates			75.10%								75.10%
General Partner's Interest | Minimum
Agreement of limited partnership
Percentage of ownership of non-affiliates of the General Partner allowing majority owner to acquire outstanding units held by non-affiliated persons											25.00%
General Partner's Interest | Minimum Quarterly Distributions
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.025%
General Partner's Interest | First Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											0.025%
General Partner's Interest | Second Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											13.156%
General Partner's Interest | Third Target
Agreement of limited partnership
Income and distribution allocation (as a percent)											23.257%
General Partner's Interest | Final Target and Beyond
Agreement of limited partnership
Income and distribution allocation (as a percent)											48.51%
Subsequent Event
Agreement of limited partnership
Cash distribution declared per common limited partnership unit (in dollars per unit) | $ / shares	$ 2.03
Distribution Made to Limited and General Partners, Distributions Declared, Total		$ 58,600,000
Subsequent Event | Common units
Agreement of limited partnership
Declared and paid partnership distributions		$ 37,600,000
Cash distribution declared per common limited partnership unit (in dollars per unit) | $ / shares		$ 2.03
Subsequent Event | Class B Common Units
Agreement of limited partnership
Declared and paid partnership distributions		$ 600,000
Cash distribution declared per common limited partnership unit (in dollars per unit) | $ / shares		$ 3.10
Subsequent Event | General Partner's Interest
Agreement of limited partnership
Declared and paid partnership distributions		$ 20,400,000
CF Industries Holdings Inc [Member] | Common units
Agreement of limited partnership
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest											75.10%
Terra Nitrogen GP Inc [Member] | Terra Nitrogen Company LP [Member] | Subsequent Event
Agreement of limited partnership
Business Acquisition, Share Price | $ / shares	$ 84.033

Net Earnings per Common Unit (D

Net Earnings per Common Unit (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic earnings per common unit:
Net earnings	$ 49.4	$ 22.8	$ 39.5	$ 42.2	$ 44.1	$ 28.8	$ 98.7	$ 37.7	$ 153.9	$ 209.3	$ 306.9
(Distributions in excess of earnings) undistributed earnings									$ (0.7)	$ 13.4	$ (2)
Weighted-average common units outstanding									18,500,000	18,500,000	18,500,000
Net earnings per common unit	$ 1.44	$ 0.92	$ 1.48	$ 2.10	$ 1.85	$ 1.04	$ 3.22	$ 1.44	$ 5.93	$ 7.56	$ 10.06
Dilutive TNCLP units outstanding									0	0	0
Common Units | Common units
Basic earnings per common unit:
Distributions declared									$ 110.3	$ 130.9	$ 187.4
Allocation percentage for undistributed earnings or distributions in excess of earnings									71.33%	66.82%	60.67%
Allocation of (distributions in excess of earnings) undistributed earnings									$ (0.5)	$ 9	$ (1.2)
Net earnings allocated									109.8	139.9	186.2
Common Units | Class B Common Units
Basic earnings per common unit:
Distributions declared									$ 1.5	$ 1.9	$ 3.1
Allocation percentage for undistributed earnings or distributions in excess of earnings									0.97%	0.97%	0.97%
Allocation of (distributions in excess of earnings) undistributed earnings									$ 0	$ 0.1	$ (0.1)
Net earnings allocated									1.5	2	3
General Partner's Interest
Basic earnings per common unit:
Distributions declared									$ 42.8	$ 63.1	$ 118.4
Allocation percentage for undistributed earnings or distributions in excess of earnings									27.70%	32.21%	38.36%
Allocation of (distributions in excess of earnings) undistributed earnings									$ (0.2)	$ 4.3	$ (0.7)
Net earnings allocable to General Partner (2)									42.6	67.4	117.7
General Partner and TLPH
Basic earnings per common unit:
Net earnings allocable to General Partner (2)									$ 1.5	$ 2.1	$ 3.1

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Finished goods	$ 3.5	$ 6.8
Raw materials, spare parts and supplies	1.8	1.8
Total	$ 5.3	$ 8.6

Derivative Financial Instrume35

Derivative Financial Instruments (Details) MMBTU in Millions	12 Months Ended
	Dec. 31, 2017USD ($)MMBTU	Dec. 31, 2016USD ($)MMBTU	Dec. 31, 2015USD ($)
Effect of Derivatives on Consolidated Statement of Operations
Unrealized net mark-to-market gains (losses)	$ (10,600,000)	$ 35,300,000	$ (24,300,000)
Open derivative contracts for natural gas (in MMBtus) | MMBTU	8.4	29.4
Percentage of natural gas consumption covered by derivatives	48.00%
Aggregate fair value of the derivative instruments with credit-risk-related contingent features in net liability position	$ 3,200,000	$ 1,600,000
Cash Collateral for Borrowed Securities	0	0
Total derivative assets
Gross and net amounts presented in consolidated balance sheet	0	9,000,000
Gross amounts not offset in consolidated balance sheet
Financial instruments	0	1,600,000
Cash collateral received (pledged)	0	0
Net amount	0	7,400,000
Total derivative liabilities
Gross and net amounts presented in consolidated balance sheet	(3,200,000)	(1,600,000)
Gross amounts not offset in consolidated balance sheet
Financial instruments	0	(1,600,000)
Cash collateral received (pledged)	0	0
Net amount	(3,200,000)	0
Net assets (liabilities)
Gross and net amounts presented in consolidated balance sheet	(3,200,000)	7,400,000
Natural gas derivatives not designated as hedging instruments
Derivative financial instruments
Unrealized gains in other current assets	0	7,900,000
Derivative Asset, Noncurrent	0	1,100,000
Price Risk Derivative Instruments Not Designated as Hedging Instruments Asset, at Fair Value	0	9,000,000
Unrealized losses in other current liabilities	(3,200,000)	0
Unrealized losses in other liabilities	0	(1,600,000)
Price Risk Derivative Instruments Not Designated as Hedging Instruments Liability, at Fair Value	(3,200,000)	(1,600,000)
Net derivative (liabilities) assets	(3,200,000)	7,400,000
Effect of Derivatives on Consolidated Statement of Operations
Unrealized net mark-to-market gains (losses)	(10,600,000)	35,300,000	(23,100,000)
Realized net losses	(3,000,000)	(16,700,000)	(10,600,000)
Net derivative (losses) gains	$ (13,600,000)	$ 18,600,000	$ (33,700,000)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring basis - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Significant Observable Inputs
Fair value measurements
Cash Equivalents, at Fair Value	$ 0	$ 0
Unrealized gains on natural gas derivatives	0	9
Total assets at fair value	0	9
Unrealized losses on natural gas derivatives	(3.2)	(1.6)
Total liabilities at fair value	(3.2)	(1.6)
Total
Fair value measurements
Cash Equivalents, at Fair Value	80.5	32
Unrealized gains on natural gas derivatives	0	9
Total assets at fair value	80.5	41
Unrealized losses on natural gas derivatives	(3.2)	(1.6)
Total liabilities at fair value	(3.2)	(1.6)
Total | Quoted Market Prices in Active Markets (Level 1)
Fair value measurements
Cash Equivalents, at Fair Value	80.5	32
Unrealized gains on natural gas derivatives	0	0
Total assets at fair value	80.5	32
Unrealized losses on natural gas derivatives	$ 0	$ 0

Property, Plant and Equipment37

Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, plant and equipment, net
Gross property, plant and equipment	$ 627.7	$ 602.3
Less: Accumulated depreciation and amortization	337.5	301
Net property, plant and equipment	290.2	301.3
Construction in Progress Expenditures Incurred but Not yet Paid	0.6	1.8	$ (2.2)
Losses on Disposition of Property Plant Equipment	0	(0.1)	(2)
Net capitalized turnaround costs:
Beginning balance	26.6	37.8	16.7
Additions	2.3	4.9	33.6
Depreciation	(14.2)	(16.1)	(12.5)
Ending balance	14.7	26.6	$ 37.8
Land
Property, plant and equipment, net
Gross property, plant and equipment	1.4	1.4
Buildings and improvements
Property, plant and equipment, net
Gross property, plant and equipment	16.9	16.7
Machinery and equipment
Property, plant and equipment, net
Gross property, plant and equipment	568.3	562.3
Construction in progress
Property, plant and equipment, net
Gross property, plant and equipment	$ 41.1	$ 21.9

Related Party Transactions (Det

Related Party Transactions (Details)	12 Months Ended
	Dec. 31, 2017USD ($)Term$ / Car	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Affiliate of General Partner
Related party transactions
Payroll, payroll-related expenses and other employee related benefits	$ 27,900,000
Due from (to) affiliates of the General Partner, net	$ 12,900,000	$ (100,000)
Affiliate of General Partner | Services and Offtake Agreement
Related party transactions
Extended term of agreement	1 year
Affiliate of General Partner | Lease Agreements
Related party transactions
Rental income received	$ 600,000	600,000	$ 600,000
Affiliate of General Partner | Lease Agreements | Ammonia assets
Related party transactions
Term of agreement	5 years
Number of times lease term is automatically extended under agreement | Term	3
Base quarterly rent of leased asset	$ 100,000
Affiliate of General Partner | Lease Agreements | Rail cars
Related party transactions
Extended term of agreement	1 year
Term of agreement	1 year
Quarterly rent per leased asset (in dollars per car) | $ / Car	3,600
CF Industries | Services and Offtake Agreement
Related party transactions
Allocated expenses	$ 15,900,000	$ 15,700,000	$ 15,700,000

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) $ in Millions	Dec. 31, 2017USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Estimated cost of AROs expressed in 2017 dollars	$ 4

Quarterly Financial Data (Una40

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 02, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 97.5	$ 84.6	$ 96.1	$ 119	$ 93.4	$ 90.2	$ 126.7	$ 108	$ 397.2	$ 418.3	$ 581.7
Gross margin	39.4	27.2	43.5	46.6	48.2	32.8	102.7	43.1	156.7	226.8	325.8
Net earnings	$ 49.4	$ 22.8	$ 39.5	$ 42.2	$ 44.1	$ 28.8	$ 98.7	$ 37.7	$ 153.9	$ 209.3	$ 306.9
Net earnings per Common Unit (in dollars per unit)	$ 1.44	$ 0.92	$ 1.48	$ 2.10	$ 1.85	$ 1.04	$ 3.22	$ 1.44	$ 5.93	$ 7.56	$ 10.06
Gain on sale of equity method investment									$ (14.3)	$ 0	$ 0
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Oklahoma CO2 Partnership [Member]
Gain on sale of equity method investment	$ (14.3)
Partnership equity interest (as a percent)												50.00%

Sale of Equity Method Investm41

Sale of Equity Method Investment (Details) - USD ($) $ in Millions	Oct. 02, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investment			$ 16.3	$ 0	$ 0
Gain on sale of equity method investment			$ (14.3)	$ 0	$ 0
Oklahoma CO2 Partnership [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Schedule of Equity Method Investments [Line Items]
Partnership equity interest (as a percent)	50.00%
Proceeds from sale of equity method investment	$ 16.3
Gain on sale of equity method investment		$ (14.3)

Subsequent Event (Details)

Subsequent Event (Details)	12 Months Ended
	Dec. 31, 2017trading_day	Feb. 07, 2018$ / shares
Subsequent Event [Line Items]
Number of average trading days' closing prices used to determine the purchase price of outstanding units of non-affiliates | trading_day	20
Terra Nitrogen Company LP [Member] | Terra Nitrogen GP Inc [Member] | Subsequent Event
Subsequent Event [Line Items]
Business Acquisition, Share Price | $ / shares		$ 84.033