Acquisitions (Acquisition of MarEn Bakken) (Details) bbl / d in Thousands, $ in Millions			11 Months Ended	12 Months Ended
		Feb. 15, 2017 USD ($) Quarterly_reporting_period bbl / d	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments				$ 713.0	$ 341.0	$ 761.0
Income from equity method investments	[1],[2]			290.0	247.0	$ 78.0
MPC
Schedule of Equity Method Investments [Line Items]
Incentive distribution rights forfeited per quarter		$ 1.6
Number of quarters IDRs forfeited | Quarterly_reporting_period		12
Prorated incentive distribution rights forfeited		$ 0.8
MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments		$ 2,000.0
MarEn Bakken
Schedule of Equity Method Investments [Line Items]
Barrels Handled | bbl / d		520
Payments to acquire equity method investments		$ 500.0
Percentage of ownership interest in joint venture acquired		25.00%
Income from equity method investments			$ 15.0	$ 72.0	$ 48.0
Bakken Pipeline System
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in joint venture acquired		37.00%
Equity method investment, ownership percentage		9.00%

[1] “Income from equity method investments” includes the impact of any basis differential amortization or accretion.

[2] The financial information for equity method investments for 2019 includes financial information of equity method investments acquired as part of the Merger. The financial information for equity method investments for 2018 includes financial information of equity method investments acquired as part of the Merger for the last three months of 2018. The financial information for equity method investments for 2017 does not include financial information of equity method investments acquired as part of the Merger. See Note 1 for additional information