Segment information - Reconciliation of Adjusted EBITDA to Income Before Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Consolidated Adjusted EBITDA	$ 327	$ 315	$ 965	$ 1,181
Impairment of non-current assets	3	3	10	12
Depreciation and amortization	163	159	525	470
Interest expense, net of capitalization	64	61	191	178
Other income and (expense)	16	19	38	50
Earnings (losses) from equity method investments	(3)	(9)	(3)
Consolidated Income Before Income Tax	$ 110	$ 102	$ 274	$ 571