Discontinued Operations - Summarized Results of Discontinued Operations (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Revenue										$ 75	$ 291
Disposal Group, Including Discontinued Operation, Depreciation and Amortization										8	131
Disposal Group, Including Discontinued Operation, Lease Operating Expense										7	50
Disposal Group Including Discontinued Operation Gathering and Transportation Expense										12	70
Disposal Group, Including Discontinued Operation Taxes other than income										5	23
Disposal Group Including Discontinued Operation Exploration Expense										3	14
Disposal Group, Including Discontinued Operation, General and Administrative Expense										1	8
Disposal group contract obligation expense										0	5
Disposal Group (gain) loss on sale of Assets and Impairment charges										0	50
Accretion Expense										6	6
Disposal Group, Including Discontinued Operation, Other Expense										5	(3)	[1]
Disposal Group, Including Discontinued Operation, Operating Expense										47	354
Disposal Group, Including Discontinued Operation, Operating Income (Loss)										28	(63)
Disposal Group Including Discontinued Operation Income before Tax										(120)	(63)
Discontinued Operation, Tax Effect of Discontinued Operation										(29)	(23)
Income (loss) from discontinued operations	$ (1)	$ (1)	$ 0	$ 0	$ 1	$ (1)	$ (2)	$ (89)	$ (2)	(91)	(40)
Domestic
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Provision for Loss (Gain) on Disposal, before Income Tax										$ (148)	$ 0

[1] Includes severance tax refund received in 2017.