Description of Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2017
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 well as interests in entities that own natural gas and refinery gas pipelines which transport offshore natural gas to market hubs and deliver refinery gas from refineries and plants to chemical sites along the Gulf Coast.
Basis of Presentation	Basis of Presentation Our condensed consolidated financial statements include all 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. During interim periods, we follow the accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2016 (our “2016 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, 2017 and 2016 include all adjustments we believe are necessary for a fair statement of the results for the interim periods presented. These adjustments are of a normal recurring nature unless otherwise disclosed. Operating results for the interim periods are not necessarily indicative of the results that may be expected for the full year. 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 2016 Annual Report. The acquisition of Delta, Na Kika and Refinery Gas Pipeline (the “Shell Delta, Na Kika and Refinery Gas Pipeline Operations” or “Delta, Na Kika and Refinery Gas Pipeline”) was a transfer of businesses between entities under common control, which requires it to be accounted for as if the transfer had occurred at the beginning of the period of transfer, with prior periods retrospectively adjusted to furnish comparative financial information. Accordingly, the accompanying financial statements and notes have been retrospectively adjusted to include the historical results and financial position of the Shell Delta, Na Kika and Refinery Gas Pipeline Operations prior to the effective date of the acquisition. See Note 2 - Acquisitions and Divestitures for additional information.
Revenue Recognition	Revenue Recognition Certain transportation services agreements with a related party are considered operating leases under GAAP. Revenues from these agreements are recorded within Lease revenue - related parties in the condensed consolidated statements of income. See Note 3-Related Party Transactions for additional information.
Recently Adopted and Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In October 2016, the Financial Accounting Standards Board (“FASB”) issued 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 variable interest entity. The update was effective for us as of January 1, 2017. The adoption of this update did not have a material impact on our financial statements. In March 2016, the FASB issued 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. The update was effective for us as of January 1, 2017. The adoption of this update did not have a material impact on our financial statements. Recent Accounting Pronouncements In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which will supersede nearly all existing revenue recognition guidance under GAAP. The ASU's core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The update is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2017. The update allows for either “full retrospective” adoption, meaning the standard is applied to all of the periods presented, or “modified retrospective” adoption, meaning the standard is applied only to the most current period presented in the financial statements. We will adopt the requirements of the new standard in the first quarter of 2018 under the modified retrospective transition method. As part of our implementation efforts to date, all of our revenue contracts have been subject to review to evaluate the effect of the new standard on our revenue recognition practices. We have also made progress in evaluating new disclosure requirements and identifying impacts to our business processes, systems and controls to support recognition and disclosure under the new guidance. We expect the adoption of the new standard will change the way we recognize revenue from our committed shippers under transportation services agreements. We anticipate the new standard will result in earlier recognition of revenue related to cash collected from customers for shortfalls under these agreements, which is recorded as deferred revenue. We currently recognize deferred revenue under these arrangements into revenue once all contingencies or potential performance obligations associated with the related volumes have been satisfied or expired. Upon adoption of the new standard and application of the breakage model to our deferred revenue, we anticipate a cumulative transition adjustment resulting from the earlier recognition of revenue with a corresponding adjustment to beginning retained earnings and are in the process of quantifying the impact. We have also identified potential contracts or elements of contracts that may require a change in presentation on our income statement, specifically related to the service component of leases, product loss allowance, gross versus net presentation and reimbursements of capital expenditures. Currently, we do not anticipate these to materially impact our financial statements as there will be no net impact to income before taxes. However, this is still under review and subject to our ongoing assessment of the guidance. For additional information on accounting pronouncements issued prior to September 2017, refer to Note 2—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements of our 2016 Annual Report.