Other Liabilities - Long-Term Table (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Other Long-Term Liabilities [Line Items]
Conveyance obligation	$ 0		$ 0		$ 156
Unrecognized tax benefits	81		81		101
Other	96		96		97
Total other long-term liabilities	177		177		354
Other income (expense)	62	$ (1)	62	$ 2
Capitalized costs, proved properties	69,976		69,976		$ 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 (expense)	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