Basis of Presentation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Reclassification of expense from Operating costs and expenses, Exploration expenses, and General and administrative expenses to Other, net due to adopting ASU 2017-07		$ 2
Prior Period Adjustment [Abstract]
Sales and other operating revenues	$ 1,346	1,258
Marketing, including purchased oil and gas	358	200
Restatement Adjustment
Prior Period Adjustment [Abstract]
Sales and other operating revenues		(19)
Marketing, including purchased oil and gas		(19)
Scenario Previously Reported
Prior Period Adjustment [Abstract]
Sales and other operating revenues		1,277
Marketing, including purchased oil and gas		$ 219
ASU 2017-12
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Cumulative effect of hedging ineffectiveness	$ 1