Description of Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business We are a fee-based, growth-oriented master limited partnership formed by Shell to own, operate, develop and acquire pipelines and other midstream assets. Our assets consist of interests in entities that own crude oil and refined products pipelines serving as key infrastructure to transport onshore and offshore crude oil production to Gulf Coast and Midwest refining markets and to deliver refined products from those markets to major demand centers. As of September 30, 2016, we own interests in four crude oil pipeline systems, three refined products systems and a crude storage terminal. The crude oil pipeline systems, which are held by Zydeco Pipeline Company LLC (“Zydeco”), Mars Oil Pipeline Company (“Mars”), Poseidon Oil Pipeline Company, LLC (“Poseidon”) and the Auger Pipeline System (“Auger”), are strategically located along the Texas and Louisiana Gulf Coast and in the Gulf of Mexico. These systems link major onshore and offshore production areas with key refining markets. The refined products pipeline systems are held by Bengal Pipeline Company LLC (“Bengal”) and Colonial Pipeline Company (“Colonial”), which connect Gulf Coast and southeastern U.S. refineries to major demand centers from Alabama to New York, and Explorer Pipeline Company (“Explorer”), which serves more than 70 major cities in 16 states from the Gulf Coast to the Midwest. The crude storage terminal, called the Lockport Terminal (“Lockport”), is located southwest of Chicago and serves Midwest refineries. Auger and Lockport are owned by our wholly owned subsidiary, Pecten Midstream LLC (“Pecten”). As of September 30, 2016, we own a 100% interest in Pecten, a 92.5% interest in Zydeco, a 28.6% interest in Mars, a 36.0% interest in Poseidon, a 50.0% interest in Bengal, a 6.0% interest in Colonial and a 2.62% interest in Explorer. Each of Pecten and Zydeco is consolidated within our condensed consolidated financial statements as a subsidiary. The 7.5% ownership interest in Zydeco retained by SPLC is reflected as noncontrolling interest in our condensed consolidated financial statements. We account for each of our investments in Mars, Bengal and Poseidon using the equity method of accounting, and we account for each of our investments in Colonial and Explorer using the cost method of accounting. We generate the majority of our revenue under long-term agreements by charging fees for the transportation and storage of crude oil and refined products through our pipelines and storage tanks. Our operations consist of one reportable segment.
Basis of Presentation	Basis of Presentation Our condensed consolidated financial statements include all majority owned and non-majority owned subsidiaries required to be consolidated under generally accepted accounting principles in the United States (“GAAP”). Our reporting currency is U.S. dollars, and all references to dollars are U.S. dollars. The accompanying unaudited condensed consolidated financial statements and related notes have been prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by GAAP for complete annual financial statements. The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. During interim periods, we follow the accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2015 (our “2015 Annual Report”), filed with the United States Securities and Exchange Commission (“SEC”). The unaudited condensed consolidated financial statements for the three and nine months ended September 30, 2016 and 2015 include all adjustments we believe are necessary for a fair statement of the results for the interim periods. These adjustments are of a normal recurring nature unless otherwise disclosed. Operating results for the three and nine months ended September 30, 2016 are not necessarily indicative of the results that may be expected for the full year ended December 31, 2016. These unaudited condensed consolidated financial statements and other information included in this Quarterly Report on Form 10-Q should be read in conjunction with our consolidated financial statements and notes thereto included in our 2015 Annual Report. The September 30, 2015 condensed consolidated financial statements have been retrospectively adjusted for the acquisition of the Shell Auger and Lockport Operations (the "Shell Auger and Lockport Operations"). These retrospective adjustments include expense allocations for certain functions historically performed by our Parent on behalf of the Shell Auger and Lockport Operations, including allocations of general corporate expenses related to finance, legal, information technology, human resources, communications, ethics and compliance, shared services, employee benefits and incentives, insurance, and share-based compensation. See Note 2—Acquisitions to our condensed consolidated financial statements. Prior to the contribution of fixed assets and certain agreements on October 1, 2015 related to the Shell Auger and Lockport Operations, the cash generated and used by these operations was deposited to SPLC’s centralized account which was comingled with the cash of other pipeline entities controlled by SPLC. SPLC funded these operating and investing activities as needed. Accordingly, we did not record any cash and cash equivalents held by SPLC on behalf of the Shell Auger and Lockport Operations for any period prior to October 1, 2015. We reflected the cash generated by these operations and expenses paid by SPLC on behalf of these operations as Net distributions to Parent within the accompanying condensed consolidated statements of cash flows. Our asset acquisitions are accounted for prospectively from the effective date of the transaction. The condensed consolidated financial statements as of and for the nine months ended September 30, 2016 and 2015 reflect the results of the following assets acquired prospectively from the dates indicated: •The interest in Explorer acquired August 9, 2016; •The additional interests in Zydeco, Bengal and Colonial acquired effective April 1, 2016; •The additional interests in Zydeco and Colonial acquired effective April 1, 2015; and •The interest in Poseidon acquired effective July 1, 2015.
Recent Accounting Pronouncements	Recent Accounting Pronouncements For additional information on accounting pronouncements issued prior to December 2015, refer to Note 2—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements of our 2015 Annual Report. In October 2016, the Financial Accounting Standards Board (“FASB”) issued accounting standards update (ASU 2016-17) to topic 810, Consolidation, making changes on how a reporting entity should treat indirect interests in an entity held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of a VIE. This update is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Adoption of this update will not have an impact on our financial statements at this time. In August 2016, the FASB issued accounting standards update (ASU 2016-15) to topic 230, Statement of Cash Flows, making changes to the classification of certain cash receipts and cash payments in order to reduce diversity in presentation. This update is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. The update addresses eight specific cash flow issues, of which only one is applicable to our financial statements. The applicable update relates to distributions received from equity method investees and prescribes two options for presenting these cash flows: cumulative earnings approach or nature of the distribution approach. We currently apply cumulative earnings approach, when the distributions received are considered returns on investment and classified as cash inflows from operating activities. Adoption of this update will not have a material impact on our financial statements. In March 2016, the FASB issued accounting standards update (ASU 2016-07) to topic 323, Investments – Equity Method and Joint Ventures, to eliminate the need for an entity to retroactively adopt the equity method of accounting when an investment becomes qualified for the use of the equity method of accounting due to an increase in level of ownership or degree of influence. This provision is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. We are currently evaluating the effect of adoption of this guidance on our financial position or results of operations. In January 2016, the FASB issued accounting standards update (ASU 2016-01) to topic 825, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities, requiring equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income. Additionally, the update allows equity investments that do not have readily determinable fair values to be re-measured at fair value either upon the occurrence of an observable price change or upon identification of impairment, and requires additional disclosure around those investments. This update is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. We are currently evaluating the effect of this guidance which is not expected to have a significant impact on our financial position or results of operations. In February 2015, the FASB issued an accounting standards update (ASU 2015-02) making targeted changes to the current consolidation guidance. The new standard changes the considerations related to substantive rights, related parties, and decision making fees when applying the variable interest entity consolidation model and eliminates certain guidance for limited partnerships and similar entities under the voting interest consolidation model. The update is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2015. Adoption of this standard did not have a material impact on the consolidated results of operations, financial position or cash flows.