Segment Information - Sales Revenues by Geographic Area Table (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue from External Customer [Line Items]
Sales revenues	$ 10,969	$ 8,447	$ 9,486
United States [Member]
Revenue from External Customer [Line Items]
Sales revenues	9,176	7,049	7,819
Algeria [Member]
Revenue from External Customer [Line Items]
Sales revenues	1,249	1,103	1,189
Other International [Member]
Revenue from External Customer [Line Items]
Sales revenues	$ 544	$ 295	$ 478