Other Liabilities - Long-Term Table (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Other Long-Term Liabilities [Line Items]
Conveyance obligation	$ 0		$ 0		$ 156
Unrecognized tax benefits	53		53		101
Other	107		107		97
Total other long-term liabilities	160		160		354
Other income	1	$ 4	63	$ 6
Capitalized costs, proved properties	70,620		70,620		$ 68,858
ORRI [Member]
Other Long-Term Liabilities [Line Items]
Conveyance obligation	183		183
Consideration			199
Conveyance obligation, noncurrent	30		30
Conveyance obligation, current	153		153
Other income			61
Oil and Gas Properties [Member] | ORRI [Member]
Other Long-Term Liabilities [Line Items]
Capitalized costs, proved properties	$ 77		77
Liability [Member] | ORRI [Member]
Other Long-Term Liabilities [Line Items]
Extinguishment of liabilities			$ 122