Goodwill - Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Balance at January 1	$ 1,858	$ 375	$ 1,858
Reclassification		0	0
Impairment		0	(1,483)
Balance at December 31		375	375
Exploration and Production
Goodwill [Line Items]
Balance at January 1	1,858	0	1,858
Reclassification		0	(375)
Impairment		0	(1,483)
Balance at December 31		0	0
Bakken Midstream
Goodwill [Line Items]
Balance at January 1	0	375	0
Reclassification	$ 375	0	375
Impairment		0	0
Balance at December 31		$ 375	$ 375