Exit Cost - Transportation Commitments - Income Statement Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Long-term Purchase Commitment [Line Items]
Cost of Purchased Oil and Gas	$ 431	$ 296	$ 0
Sales of Purchased Oil and Gas
Long-term Purchase Commitment [Line Items]
Sales of Purchased Oil and Gas	90	113	0
Cost of Purchased Oil and Gas	85	108	0
Utilized Firm Transportation Expense
Long-term Purchase Commitment [Line Items]
Cost of Purchased Oil and Gas	57	29	0
Unutilized Firm Transportation Expense
Long-term Purchase Commitment [Line Items]
Cost of Purchased Oil and Gas	1	3	0
Cost of Purchased Gas, Total
Long-term Purchase Commitment [Line Items]
Cost of Purchased Oil and Gas	$ 143	$ 140	$ 0