Divestitures, Decommissioning and Restructuring Activities (Narrative) (Details) $ in Millions		1 Months Ended							3 Months Ended			9 Months Ended		42 Months Ended
	Jun. 30, 2019 a	Oct. 31, 2020 employee	Jul. 31, 2020 USD ($)	Jun. 30, 2020 employee	May 31, 2020 USD ($) a	Jul. 31, 2019 USD ($) a	Jun. 30, 2019 USD ($) a	May 31, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) a	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jul. 01, 2022	Jan. 01, 2021 USD ($)	Dec. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds												$ 58	$ 82
Gain (loss) on disposition of assets, net									$ 2	$ 20		7	(477)
Contingent Consideration, Valuation Adjustment									22	(48)		(42)	(61)
Contingent consideration																$ 91
South Texas deficiency fee obligation									0	0		69	0
Restricted cash									66			66				74
Accelerated depreciation									0	0		0	23
Staffing reduction, employees | employee				50
Restructuring charges									74	$ 1		75	159
Employee severance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncash stock-based compensation expense													23
Restructuring charges												72	133
Employee severance | 2020 Corporate Restructuring
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring charges									74			74
Accelerated vesting of certain equity awards | 2020 Corporate Restructuring
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncash stock-based compensation expense									3			3
Subsequent event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Staffing reduction, employees | employee		300
Significant Other Observable Inputs (Level 2)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent consideration																$ 91
Vertical Wells in Upton County
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sale					$ 6
Certain Vertical Wells in Martin County of the Permian Basin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sale						$ 26	$ 31
South Texas Divestiture
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds								$ 2
Cash proceeds, before normal closing adjustments								210
Receivable from buyer									71			71
Gain (loss) on disposition of assets, net					$ 525
Contingent consideration								136
Contingent Consideration, Valuation Adjustment												22
Deficiency fee liability									(321)			(321)
Contingent consideration period					5 years
Disposal Group, Contingent Consideration Received			$ 49
South Texas Divestiture | Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Retained obligation percentage														100.00%
Escrow															$ 50
South Texas Divestiture | Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Retained obligation percentage	100.00%
Deficiency fee liability									$ 460			460
South Texas Divestiture | Maximum | Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Retained obligation percentage														100.00%
Buyer recovery percentage														18.00%
South Texas Divestiture | South Texas Divestiture
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Receivable from buyer								$ 72
Pressure pumping assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of inventory and other property and other equipment													16
Sand mine
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accelerated depreciation											$ 12	$ 23
Impairment of inventory and other property and other equipment													$ 13
Sold | Vertical Wells in Upton County
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acres | a					1,500
Cash proceeds					$ 6
Sold | Certain Vertical Wells in Martin County of the Permian Basin
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acres | a	1,900					1,400	1,900				1,900
Cash proceeds						$ 27	$ 38