Related Party Transactions (Other Related Party Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Prepaid expenses and other current assets	$ 7	$ 10
Other assets	50	52
Deferred revenues	22	16
Other current liabilities	3	3
Other liabilities	91	94
Phillips 66
Related Party Transaction [Line Items]
Prepaid expenses and other current assets	4	7
Other assets	48	44
Deferred revenues	22	16
Other current liabilities	1	1
Other liabilities	$ 66	$ 70