Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Loss	Treasury Stock at Cost	Retained Earnings	Non-controlling Interests
Balance at Beginning of Period at Dec. 31, 2017	$ 10,619	$ 5	$ 8,438	$ (30)	$ (725)	$ 2,248	$ 683
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	574					554	20
Stock-based Compensation	17		17
Dividends	(48)					(48)
Purchase and Retirement of Common Stock	(67)		(67)
Clayton Williams Energy Acquisition	(25)		(25)
Distributions to Noncontrolling Interest Owners	(11)						(11)
Contributions from Noncontrolling Interest Owners	331						331
Other	(3)			1	(6)		2
Balance at End of Period at Mar. 31, 2018	11,387	5	8,363	(29)	(731)	2,754	1,025
Balance at Beginning of Period at Dec. 31, 2017	10,619	5	8,438	(30)	(725)	2,248	683
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	816
Balance at End of Period at Sep. 30, 2018	11,394	5	8,249	(27)	(731)	2,850	1,048
Balance at Beginning of Period at Mar. 31, 2018	11,387	5	8,363	(29)	(731)	2,754	1,025
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	(6)					(23)	17
Stock-based Compensation	29		29
Dividends	(54)					(54)
Purchase and Retirement of Common Stock	(63)		(63)
Distributions to Noncontrolling Interest Owners	(11)						(11)
Other	(1)			1			(2)
Balance at End of Period at Jun. 30, 2018	11,281	5	8,329	(28)	(731)	2,677	1,029
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	248					227	21
Stock-based Compensation	17		17
Dividends	(54)					(54)
Purchase and Retirement of Common Stock	(103)		(103)
Distributions to Noncontrolling Interest Owners	(13)						(13)
Contributions from Noncontrolling Interest Owners	17						17
Other	1		6	1			(6)
Balance at End of Period at Sep. 30, 2018	11,394	5	8,249	(27)	(731)	2,850	1,048
Balance at Beginning of Period at Dec. 31, 2018	10,484	5	8,203	(32)	(730)	1,980	1,058
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	(289)					(313)	24
Stock-based Compensation	14		14
Dividends	(53)					(53)
Distributions to Noncontrolling Interest Owners	(17)						(17)
Contributions from Noncontrolling Interest Owners	10						10
Other	(6)		2		(5)		(3)
Balance at End of Period at Mar. 31, 2019	10,143	5	8,219	(32)	(735)	1,614	1,072
Balance at Beginning of Period at Dec. 31, 2018	10,484	5	8,203	(32)	(730)	1,980	1,058
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	(245)
Balance at End of Period at Sep. 30, 2019	10,083	5	8,258	(30)	(735)	1,506	1,079
Balance at Beginning of Period at Mar. 31, 2019	10,143	5	8,219	(32)	(735)	1,614	1,072
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	8					(10)	18
Stock-based Compensation	21		21
Dividends	(58)					(58)
Distributions to Noncontrolling Interest Owners	(19)						(19)
Contributions from Noncontrolling Interest Owners	11						11
Other	(2)		4	1			(7)
Balance at End of Period at Jun. 30, 2019	10,104	5	8,244	(31)	(735)	1,546	1,075
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (Loss) Income	36					17	19
Stock-based Compensation	16		16
Dividends	(57)					(57)
Distributions to Noncontrolling Interest Owners	(19)						(19)
Contributions from Noncontrolling Interest Owners	6						6
Other	(3)		(2)	1			(2)
Balance at End of Period at Sep. 30, 2019	$ 10,083	$ 5	$ 8,258	$ (30)	$ (735)	$ 1,506	$ 1,079