Organization and Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of accounting, policy	We are required under U.S. GAAP to make estimates and assumptions that affect the amounts of assets and liabilities and revenues and expenses reported as of and during the periods presented.
Use of Estimates, Policy [Policy Text Block]	We review our estimates on an ongoing basis using currently available information. Changes in facts and circumstances may result in revised estimates, and actual results could differ from those estimates. The results of operations of the Partnership, or our Predecessors, for any interim period are not necessarily indicative of results for the full year.
New accounting pronouncement, policy	NEW ACCOUNTING STANDARDS AND DISCLOSURES REVENUE RECOGNITION. In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”), and has since amended the standard with ASU 2015-14, “Revenue From Contracts with Customers: Deferral of the Effective Date,” ASU 2016-08, ”Revenue From Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” ASU 2016-10, “Revenue From Contracts with Customers: Identifying Performance Obligations and Licensing,” and ASU 2016-12, “Revenue From Contracts with Customers: Narrow-Scope Improvements and Practical Expedients.” These standards replace existing revenue recognition rules with a single comprehensive model to use in accounting for revenue arising from contracts with customers. We are required to adopt ASU 2014-09 on January 1, 2018. We expect to transition to the new standard under the modified retrospective transition method, whereby a cumulative effect adjustment will be recognized upon adoption and the guidance will be applied prospectively. We are progressing through our implementation plan and continue to evaluate the impact of the standard’s revenue recognition model on our contracts with customers in the gathering and processing and terminalling and transportation segments along with our business processes, accounting systems, controls and financial statement disclosures. While we have made substantial progress in our review and documentation of the impact of the standard on our revenue agreements, we continue to assess the impact in certain other areas where industry consensus continues to be formed such as agreements with terms that include non-cash consideration, contributions in aid of construction, tiered pricing structures and other unique considerations. At this time, we are unable to estimate the full impact of the standard until the industry reaches a consensus on certain industry specific issues. However, we do expect some impact on presentation and disclosures in our financial statements relating to contracts that include minimum volume commitments with claw back provisions, or where revenue is based on a percentage of gross proceeds. LEASES. In February 2016, the FASB issued ASU 2016-02, “Leases” (“ASU 2016-02”), which amends existing accounting standards for lease accounting and adds additional disclosures about leasing arrangements. Under the new guidance, lessees are required to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either a finance lease or operating lease with the classification affecting the pattern of expense recognition in the income statement and presentation of cash flows in the statement of cash flows. ASU 2016-02 is effective for annual reporting periods beginning after December 15, 2018, and interim reporting periods within those annual reporting periods. Early adoption is permitted and modified retrospective application is required, however, we do not intend to early adopt the standard. While it is early in our assessment of the impacts from this standard, we expect the recognition of right-of-use assets and lease liabilities not currently reflected in our balance sheet could have a material impact on total assets and liabilities. Additionally, we expect the presentation changes required for amounts currently reflected in our statement of operations to impact certain financial statement line items. We cannot estimate the impact on our business processes, accounting systems, controls and financial statement disclosures due to the implementation of this standard given the preliminary stage of our assessment. CREDIT LOSSES. In June 2016, the FASB issued ASU 2016-13, “Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”), which amends guidance on the impairment of financial instruments. The ASU requires the estimation of credit losses based on expected losses and provides for a simplified accounting model for purchased financial assets with credit deterioration. ASU 2016-13 is effective for annual reporting periods beginning after December 15, 2019, and interim reporting periods within those annual reporting periods. Early adoption is permitted for annual reporting periods beginning after December 15, 2018. While we are still evaluating the impact of ASU 2016-13, we do not expect the adoption of this standard to have a material impact on our financial statements. DEFINITION OF A BUSINESS. In January 2017, the FASB issued ASU 2017-01, “Clarifying the Definition of a Business” (“ASU 2017-01”), which revises the definition of a business and assists in the evaluation of when a set of transferred assets and activities is a business. ASU 2017-01 is effective for interim and annual reporting periods beginning after December 15, 2017, and should be applied prospectively on or after the effective date. Early adoption is permitted under certain circumstances. At this time, we are evaluating the potential impact of this standard on our financial statements and whether we will early adopt this standard in 2017. GOODWILL. In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”), which eliminates the second step from the goodwill impairment test that required goodwill impairments to be measured as the amount that a reporting unit’s carrying amount of goodwill exceeded its implied fair value of goodwill. Instead, an entity can perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount with any impairment being limited to the total amount of goodwill allocated to that reporting unit. ASU 2017-04 is effective for interim and annual reporting periods beginning after December 15, 2019 and should be applied on a prospective basis. As permitted under ASU 2017-04, we have elected to early adopt this standard for our 2017 goodwill impairment tests to be performed as of November 1, 2017. The adoption of this standard is not expected to have a material impact on our financial statements. PENSION AND POSTRETIREMENT COSTS. In March 2017, the FASB issued ASU 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost” (“ASU 2017-07”), which requires the current service-cost component of net benefit costs to be presented similarly with other current compensation costs for related employees on the condensed statement of consolidated operations and stipulates that only the service cost component of net benefit cost is eligible for capitalization. Additionally, the Partnership will present other components of net benefit costs elsewhere on the condensed statement of consolidated operations since these costs are allocated to the Partnership’s financial statements by Andeavor. ASU 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted in the first quarter of 2017 only. The amendments to the presentation of the condensed statement of consolidated operations in this update should be applied retrospectively while the change in capitalized benefit cost is to be applied prospectively. We have evaluated the impact of this standard on our financial statements and determined there will be no impact to net earnings, but it is expected to have an immaterial impact on other line items such as operating income. We have elected not to early adopt and will implement when the standard becomes effective.

NEW ACCOUNTING STANDARDS AND DISCLOSURES

REVENUE RECOGNITION. In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”), and has since amended the standard with ASU 2015-14, “Revenue From Contracts with Customers: Deferral of the Effective Date,” ASU 2016-08, ”Revenue From Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” ASU 2016-10, “Revenue From Contracts with Customers: Identifying Performance Obligations and Licensing,” and ASU 2016-12, “Revenue From Contracts with Customers: Narrow-Scope Improvements and Practical Expedients.” These standards replace existing revenue recognition rules with a single comprehensive model to use in accounting for revenue arising from contracts with customers. We are required to adopt ASU 2014-09 on January 1, 2018. We expect to transition to the new standard under the modified retrospective transition method, whereby a cumulative effect adjustment will be recognized upon adoption and the guidance will be applied prospectively.

We are progressing through our implementation plan and continue to evaluate the impact of the standard’s revenue recognition model on our contracts with customers in the gathering and processing and terminalling and transportation segments along with our business processes, accounting systems, controls and financial statement disclosures. While we have made substantial progress in our review and documentation of the impact of the standard on our revenue agreements, we continue to assess the impact in certain other areas where industry consensus continues to be formed such as agreements with terms that include non-cash consideration, contributions in aid of construction, tiered pricing structures and other unique considerations. At this time, we are unable to estimate the full impact of the standard until the industry reaches a consensus on certain industry specific issues. However, we do expect some impact on presentation and disclosures in our financial statements relating to contracts that include minimum volume commitments with claw back provisions, or where revenue is based on a percentage of gross proceeds.

LEASES. In February 2016, the FASB issued ASU 2016-02, “Leases” (“ASU 2016-02”), which amends existing accounting standards for lease accounting and adds additional disclosures about leasing arrangements. Under the new guidance, lessees are required to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either a finance lease or operating lease with the classification affecting the pattern of expense recognition in the income statement and presentation of cash flows in the statement of cash flows. ASU 2016-02 is effective for annual reporting periods beginning after December 15, 2018, and interim reporting periods within those annual reporting periods. Early adoption is permitted and modified retrospective application is required, however, we do not intend to early adopt the standard. While it is early in our assessment of the impacts from this standard, we expect the recognition of right-of-use assets and lease liabilities not currently reflected in our balance sheet could have a material impact on total assets and liabilities. Additionally, we expect the presentation changes required for amounts currently reflected in our statement of operations to impact certain financial statement line items. We cannot estimate the impact on our business processes, accounting systems, controls and financial statement disclosures due to the implementation of this standard given the preliminary stage of our assessment.

CREDIT LOSSES. In June 2016, the FASB issued ASU 2016-13, “Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”), which amends guidance on the impairment of financial instruments. The ASU requires the estimation of credit losses based on expected losses and provides for a simplified accounting model for purchased financial assets with credit deterioration. ASU 2016-13 is effective for annual reporting periods beginning after December 15, 2019, and interim reporting periods within those annual reporting periods. Early adoption is permitted for annual reporting periods beginning after December 15, 2018. While we are still evaluating the impact of ASU 2016-13, we do not expect the adoption of this standard to have a material impact on our financial statements.

DEFINITION OF A BUSINESS. In January 2017, the FASB issued ASU 2017-01, “Clarifying the Definition of a Business” (“ASU 2017-01”), which revises the definition of a business and assists in the evaluation of when a set of transferred assets and activities is a business. ASU 2017-01 is effective for interim and annual reporting periods beginning after December 15, 2017, and should be applied prospectively on or after the effective date. Early adoption is permitted under certain circumstances. At this time, we are evaluating the potential impact of this standard on our financial statements and whether we will early adopt this standard in 2017.

GOODWILL. In January 2017, the FASB issued ASU 2017-04, “Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”), which eliminates the second step from the goodwill impairment test that required goodwill impairments to be measured as the amount that a reporting unit’s carrying amount of goodwill exceeded its implied fair value of goodwill. Instead, an entity can perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount with any impairment being limited to the total amount of goodwill allocated to that reporting unit. ASU 2017-04 is effective for interim and annual reporting periods beginning after December 15, 2019 and should be applied on a prospective basis. As permitted under ASU 2017-04, we have elected to early adopt this standard for our 2017 goodwill impairment tests to be performed as of November 1, 2017. The adoption of this standard is not expected to have a material impact on our financial statements.

PENSION AND POSTRETIREMENT COSTS. In March 2017, the FASB issued ASU 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost” (“ASU 2017-07”), which requires the current service-cost component of net benefit costs to be presented similarly with other current compensation costs for related employees on the condensed statement of consolidated operations and stipulates that only the service cost component of net benefit cost is eligible for capitalization. Additionally, the Partnership will present other components of net benefit costs elsewhere on the condensed statement of consolidated operations since these costs are allocated to the Partnership’s financial statements by Andeavor. ASU 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017, with early adoption permitted in the first quarter of 2017 only. The amendments to the presentation of the condensed statement of consolidated operations in this update should be applied retrospectively while the change in capitalized benefit cost is to be applied prospectively. We have evaluated the impact of this standard on our financial statements and determined there will be no impact to net earnings, but it is expected to have an immaterial impact on other line items such as operating income. We have elected not to early adopt and will implement when the standard becomes effective.