Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 9,671	$ 9,379
Description of performance obligations and contract balances	The majority of the Company's product sale commitments are short-term in nature with a contract term of one year or less. The Company typically satisfies its performance obligations upon transfer of control as described above in Disaggregated revenue from contracts with purchasers and records the related revenue in the month production is delivered to the purchaser. Settlement statements for sales of oil, NGL and gas and sales of purchased oil and gas may not be received for 30 to 60 days after the date the volumes are delivered, and as a result, the Company is required to estimate the amount of volumes delivered to the purchaser and the price that will be received for the sale of the product.
Accounts receivable, due or billable	$ 968	646
Oil sales
Disaggregation of Revenue [Line Items]
Revenue	4,168	3,991
NGL Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	510	695
Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	238	305
Total Oil and Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,916	4,991
Sale of Oil Purchased [Member]
Disaggregation of Revenue [Line Items]
Revenue	4,726	4,339
Sale of Gas Purchased [Member]
Disaggregation of Revenue [Line Items]
Revenue	29	49
Sales of Purchased Oil and Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue	$ 4,755	$ 4,388