Segment Information - Sales Revenues by Geographic Area Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue from External Customer [Line Items]
Sales revenues	$ 16,375	$ 14,867	$ 13,307
United States [Member]
Revenue from External Customer [Line Items]
Sales revenues	13,083	11,290	9,911
Algeria [Member]
Revenue from External Customer [Line Items]
Sales revenues	2,435	2,184	2,182
Other International [Member]
Revenue from External Customer [Line Items]
Sales revenues	$ 857	$ 1,393	$ 1,214