Debt Credit Facilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 1,600	[1]
Long-term Line of Credit	50	[1]
Letters of Credit Outstanding, Amount	0	[1]
Line of Credit Facility, Remaining Borrowing Capacity	1,550	[1]
Line of Credit Facility, Maximum Borrowing Capacity	2,100
Andeavor Logistics Dropdown Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	1,000
Long-term Line of Credit	0
Letters of Credit Outstanding, Amount	0
Line of Credit Facility, Remaining Borrowing Capacity	$ 1,000
Line of Credit Facility, Expiration Date	Jan. 29, 2021
Andeavor Logistics Revolving Credit Facility (a)
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 600	[2]
Long-term Line of Credit	50	[2]
Letters of Credit Outstanding, Amount	0	[2]
Line of Credit Facility, Remaining Borrowing Capacity	$ 550	[2]
Line of Credit Facility, Expiration Date	Jan. 29, 2021	[2]
Debt, Weighted Average Interest Rate	3.31%

[1] We are allowed to request that the loan availability be increased up to an aggregate of $2.1 billion, subject to receiving increased commitments from the lenders.

[2] The weighted average interest rate for borrowings under our Revolving Credit Facility was 3.31% at June 30, 2017.