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Investments & NCI MarEn Bakken (Details) $ in Millions |  | 6 Months Ended |
--- | --- | --- | ---
Feb. 15, 2017 USD ($) | Jun. 30, 2017 USD ($) | Jun. 30, 2016 USD ($) | Dec. 31, 2016 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |
Investments in unconsolidated affiliates |  | $ 640.0 | $ 39.0 |
Equity method investments |  | $ 3,368.0 |  | $ 2,471.0
Bakken Pipeline System [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Percentage of Ownership Interest in Joint Venture Acquired | 36.75% |  |  |
Equity Method Investment, Ownership Percentage |  | 9.1875% |  |
MarEn Bakken [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Investments in unconsolidated affiliates | $ 500.0 |  |  |
Percentage of Ownership Interest in Joint Venture Acquired |  | 25.00% |  |
Equity method investments |  | $ 519.0 |  |
MPC |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Incentive Distribution Rights Forfeited per Quarter | $ 1.6 |  |  |
Number of Quarters IDRs Forfeited | 12 |  |  |
Prorated Incentive Distribution Rights Forfeited | $ 0.8 |  |  |
MarEn Bakken Company LLC [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Investments in unconsolidated affiliates | $ 2,000.0 |  |  |

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