Segment information - Reconciliation of Consolidated EBITDA to Consolidated Net Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting [Abstract]
Consolidated Adjusted EBITDA	$ 611	$ 624
Loss from assets held for sale	5
Depreciation and amortization	203	197
Interest expense, net of capitalization	74	71
Income tax expense	72	103
Other expense	(21)	(16)
Earnings from equity method investments	2	2
Net Income	$ 238	$ 239