Debt Credit Facilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Line of Credit Facility [Line Items]
Total Capacity	$ 2,600
Amount Borrowed as of June 30, 2019	1,500
Outstanding Letters of Credit	0
Available Capacity as of June 30, 2019	1,100
Revolving Credit Facility
Line of Credit Facility [Line Items]
Outstanding Letters of Credit	0
Available Capacity as of June 30, 2019	$ 30
Expiration	Jan. 29, 2021
Dropdown Credit Facility
Line of Credit Facility [Line Items]
Outstanding Letters of Credit	$ 0
Available Capacity as of June 30, 2019	$ 570
Expiration	Jan. 29, 2021
Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Amount Borrowed as of June 30, 2019	$ 1,070
Weighted Average Interest Rate	3.90%
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,100	[1]
Revolving Credit Facility | Dropdown Credit Facility
Line of Credit Facility [Line Items]
Amount Borrowed as of June 30, 2019	$ 430
Weighted Average Interest Rate	3.92%
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,000	[1]
Revolving Credit Facility | MPC Loan Agreement
Line of Credit Facility [Line Items]
Amount Borrowed as of June 30, 2019	0
Outstanding Letters of Credit	0
Available Capacity as of June 30, 2019	$ 500
Expiration	Dec. 21, 2023
Weighted Average Interest Rate	0.00%
Line of Credit Facility, Maximum Borrowing Capacity	$ 500	[1]

[1] In conjunction with the MPLX Merger, on July 30, 2019, all outstanding borrowings and unpaid fees on our credit facilities were repaid and the agreements were terminated, including the MPC Loan Agreement.