Organization and Basis of Presentation (Policies)	9 Months Ended
Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of accounting, policy	We prepare our condensed combined consolidated financial statements in conformity with U.S. GAAP, which requires management 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.
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”), which provides accounting guidance for all revenue arising from contracts to provide goods or services to customers. ASU 2014-09 is effective for interim and annual periods beginning after December 15, 2017 given the FASB’s recent deferral of ASU 2014-09’s effective date. Entities may choose to early adopt ASU 2014-09 as of the original effective date. The standard allows for either full retrospective adoption or modified retrospective adoption. At this time, we are evaluating the standard to determine the method of adoption and the impact of ASU 2014-09 on our financial statements and related disclosures. Pushdown Accounting. In November 2014, the SEC released a Staff Accounting Bulletin overturning portions of the interpretive guidance regarding pushdown accounting. Effective November 18, 2014, the new bulletin aligns the existing guidance to the ASU issued by the FASB in October 2014. Under the new guidance, pushdown accounting can be applied in the separate financial statements of the acquired entity upon completion of the acquisition or in a subsequent period. This impacts the stand-alone financial statements of the subsidiary, but does not alter the existing reporting requirements for the parent company to record the fair value of the acquired assets, liabilities, and non-controlling interests in consolidated financial statements. If pushdown accounting is not applied in the reporting period in which the change-in-control event occurs, an acquired entity will have the option to elect to apply pushdown accounting in a subsequent reporting period. If pushdown accounting is applied, that election is irrevocable. The SEC responded by rescinding its guidance on pushdown accounting, which had required registrants to apply pushdown accounting in certain circumstances. We plan to apply pushdown accounting to applicable entities acquired as part of the Rockies Natural Gas Business Acquisition upon finalization of the purchase price allocation. Consolidation. In February 2015, the FASB issued ASU 2015-02, “Amendments to the Consolidation Analysis” (“ASU 2015-02”). This standard modifies existing consolidation guidance for reporting organizations that are required to evaluate whether they should consolidate certain legal entities. ASU 2015-02 is effective for interim and annual periods beginning after December 15, 2015, and requires either a retrospective or a modified retrospective approach to adoption. Early adoption is permitted. At this time, we are evaluating the potential impact of this standard on our financial statements, as well as the available transition methods. Treatment of Predecessor in EPU calculation. In April 2015, the FASB issued ASU 2015-06 (“ASU 2015-06”), which requires a master limited partnership to allocate earnings or losses of transferred net assets for periods prior to asset purchases from an entity under common control entirely to the general partner when calculating earnings per unit (“EPU”). ASU 2015-06 is effective for interim and annual periods beginning after December 15, 2015 and early adoption is permitted. We elected to adopt this guidance beginning in the first quarter of 2015. Adoption of ASU 2015-06 did not impact the disclosed amounts of earnings per unit attributable to limited partners; however, the allocation of earnings presented in our EPU disclosure for the three and nine months ended September 30, 2014 has been modified to conform to the requirements of the final standard. There were no asset purchases from Tesoro during the three and nine months ended September 30, 2015. Debt Issuance Costs. In April 2015, the FASB issued ASU 2015-03, “Interest - Imputation of Interest” (“ASU 2015-03”), which will simplify the presentation of debt issuance costs. Under ASU 2015-03, debt issuance costs related to a recognized debt liability will be presented in the balance sheet as a direct deduction from the carrying amount of the related debt liability. As a result, our balance sheet will reflect a reclassification of unamortized debt issuance costs from other noncurrent assets to debt. ASU 2015-03 is effective for interim and annual periods beginning after December 15, 2015, and early adoption is permitted. We adopted this standard in the first quarter of 2015 and applied the changes retrospectively to prior periods presented. The adoption of this standard resulted in the reclassification of $49 million from other noncurrent assets to debt on the balance sheet at December 31, 2014. Unamortized debt issuance costs of $43 million are recorded as a reduction to debt on the balance sheet at September 30, 2015. Business Combinations. In September 2015, the FASB issued ASU 2015-16, “Simplifying the Accounting for Measurement-Period Adjustments” (“ASU 2015-16”). The standard requires an acquirer to recognize the cumulative impact of adjustments to provisional purchase price amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. The standard also requires an entity to present separately on the face of the income statement or disclose in the notes the portion of the amount recorded in current-period earnings by line item that would have been recorded in previous reporting periods if the adjustment to the provisional amounts had been recognized as of the acquisition date. ASU 2015-16 is effective for interim and annual periods beginning after beginning after December 15, 2015 and must be applied prospectively to adjustments that occur after the effective date. Early application is permitted for financial statements that have not been issued.

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”), which provides accounting guidance for all revenue arising from contracts to provide goods or services to customers. ASU 2014-09 is effective for interim and annual periods beginning after December 15, 2017 given the FASB’s recent deferral of ASU 2014-09’s effective date. Entities may choose to early adopt ASU 2014-09 as of the original effective date. The standard allows for either full retrospective adoption or modified retrospective adoption. At this time, we are evaluating the standard to determine the method of adoption and the impact of ASU 2014-09 on our financial statements and related disclosures.

Pushdown Accounting. In November 2014, the SEC released a Staff Accounting Bulletin overturning portions of the interpretive guidance regarding pushdown accounting. Effective November 18, 2014, the new bulletin aligns the existing guidance to the ASU issued by the FASB in October 2014. Under the new guidance, pushdown accounting can be applied in the separate financial statements of the acquired entity upon completion of the acquisition or in a subsequent period. This impacts the stand-alone financial statements of the subsidiary, but does not alter the existing reporting requirements for the parent company to record the fair value of the acquired assets, liabilities, and non-controlling interests in consolidated financial statements. If pushdown accounting is not applied in the reporting period in which the change-in-control event occurs, an acquired entity will have the option to elect to apply pushdown accounting in a subsequent reporting period. If pushdown accounting is applied, that election is irrevocable. The SEC responded by rescinding its guidance on pushdown accounting, which had required registrants to apply pushdown accounting in certain circumstances. We plan to apply pushdown accounting to applicable entities acquired as part of the Rockies Natural Gas Business Acquisition upon finalization of the purchase price allocation.

Consolidation. In February 2015, the FASB issued ASU 2015-02, “Amendments to the Consolidation Analysis” (“ASU 2015-02”). This standard modifies existing consolidation guidance for reporting organizations that are required to evaluate whether they should consolidate certain legal entities. ASU 2015-02 is effective for interim and annual periods beginning after December 15, 2015, and requires either a retrospective or a modified retrospective approach to adoption. Early adoption is permitted. At this time, we are evaluating the potential impact of this standard on our financial statements, as well as the available transition methods.

Treatment of Predecessor in EPU calculation. In April 2015, the FASB issued ASU 2015-06 (“ASU 2015-06”), which requires a master limited partnership to allocate earnings or losses of transferred net assets for periods prior to asset purchases from an entity under common control entirely to the general partner when calculating earnings per unit (“EPU”). ASU 2015-06 is effective for interim and annual periods beginning after December 15, 2015 and early adoption is permitted. We elected to adopt this guidance beginning in the first quarter of 2015. Adoption of ASU 2015-06 did not impact the disclosed amounts of earnings per unit attributable to limited partners; however, the allocation of earnings presented in our EPU disclosure for the three and nine months ended September 30, 2014 has been modified to conform to the requirements of the final standard. There were no asset purchases from Tesoro during the three and nine months ended September 30, 2015.

Debt Issuance Costs. In April 2015, the FASB issued ASU 2015-03, “Interest - Imputation of Interest” (“ASU 2015-03”), which will simplify the presentation of debt issuance costs. Under ASU 2015-03, debt issuance costs related to a recognized debt liability will be presented in the balance sheet as a direct deduction from the carrying amount of the related debt liability. As a result, our balance sheet will reflect a reclassification of unamortized debt issuance costs from other noncurrent assets to debt. ASU 2015-03 is effective for interim and annual periods beginning after December 15, 2015, and early adoption is permitted. We adopted this standard in the first quarter of 2015 and applied the changes retrospectively to prior periods presented. The adoption of this standard resulted in the reclassification of $49 million from other noncurrent assets to debt on the balance sheet at December 31, 2014. Unamortized debt issuance costs of $43 million are recorded as a reduction to debt on the balance sheet at September 30, 2015.

Business Combinations. In September 2015, the FASB issued ASU 2015-16, “Simplifying the Accounting for Measurement-Period Adjustments” (“ASU 2015-16”). The standard requires an acquirer to recognize the cumulative impact of adjustments to provisional purchase price amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. The standard also requires an entity to present separately on the face of the income statement or disclose in the notes the portion of the amount recorded in current-period earnings by line item that would have been recorded in previous reporting periods if the adjustment to the provisional amounts had been recognized as of the acquisition date. ASU 2015-16 is effective for interim and annual periods beginning after beginning after December 15, 2015 and must be applied prospectively to adjustments that occur after the effective date. Early application is permitted for financial statements that have not been issued.