Divestitures (Details) - USD ($) $ in Millions			1 Months Ended	3 Months Ended	6 Months Ended
	Dec. 03, 2018	Aug. 30, 2018	Dec. 31, 2018	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contractual commitments assumed by buyer					$ 162
Potential amount to be reimbursed to buyer					82
Liability for estimated future payments			$ 88		68	$ 88
Repayments of long-term debt					0		$ 1,191
Treasury stock acquired			201	$ 21		$ 180
Commissions			$ 1
Treasury stock acquired (in shares)			44,000,000	5,260,687		39,061,269
Fayetteville Shale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest prior to disposal		100.00%
Consideration		$ 1,865
Proceeds from disposal	$ 1,650
Adjustment due to differences from economic effective date to close date	$ 215
Non-core leasehold
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration					$ 25
Senior Notes
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayment of debt			$ 914
Repayments of long-term debt			900
Cash paid for interest			$ 9