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).

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).