Impairment - Additional Information (Detail) - USD ($)			3 Months Ended	12 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impairments [Line Items]
Impairment charge, pre-tax				$ 1,616,000,000	$ 0	$ 289,000,000
Goodwill impairment charge, pre-tax				1,483,000,000
Goodwill impairment charge, after-tax				1,483,000,000
Cash proceeds from asset sales				50,000,000	2,978,000,000	4,458,000,000
Gains on asset sales, net				51,000,000	823,000,000	2,174,000,000
Gain (loss) on asset sale, after-tax					$ 0
Legacy Assets in North Dakota
Impairments [Line Items]
Impairment charge, pre-tax				133,000,000
Impairment charge, after-tax				$ 83,000,000
Onshore Reporting Unit
Impairments [Line Items]
Goodwill impairment charge, pre-tax	$ 385,000,000
Offshore Reporting Unit
Impairments [Line Items]
Goodwill impairment charge, pre-tax			$ 1,098,000,000
Bakken Midstream
Impairments [Line Items]
Goodwill impairment charge, pre-tax	$ 0
Offshore and Onshore Reporting Units
Impairments [Line Items]
Goodwill impairment charge, pre-tax		$ 0
Interests in Natuna A Field & Pangkah Asset, Offshore Indonesia
Impairments [Line Items]
Cash proceeds from asset sales						1,300,000,000
Interest in Natuna A Field, Offshore Indonesia
Impairments [Line Items]
Cash proceeds from asset sales						656,000,000
Gains on asset sales, net						388,000,000
Gain (loss) on asset sale, after-tax						343,000,000
Interests in Pangkah Asset, Offshore Indonesia
Impairments [Line Items]
Impairment charge, pre-tax						289,000,000
Impairment charge, after-tax						$ 187,000,000