Share-Based Compensation - Liability-Classified Compensation Table (Details) - Performance Share Units - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ (1)	$ 24	$ 12	$ 25
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	(1)	20	8	21
Oil and natural gas properties
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	0	1	1	1
Oil, natural gas and NGL production expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	1	2	3	2
Exploration expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ (1)	$ 1	$ 0	$ 1