Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue - service revenue	$ 7,024	$ 9,671
Accounts receivable, due or billable	661	968
Oil sales
Disaggregation of Revenue [Line Items]
Revenue - service revenue	2,871	4,168
NGL Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	490	510
Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	269	238
Total Oil and Gas Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	3,630	4,916
Sale of Oil Purchased [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	3,359	4,726
Sale of Gas Purchased [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	24	29
Sales of Purchased Commodities [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	3,394	4,755
Sale of Diesel Purchased [Member]
Disaggregation of Revenue [Line Items]
Revenue - service revenue	$ 11	$ 0