Supplementary Information - Change in Allowance for Doubtful Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting [Abstract]
Balance at beginning of year	$ 275	$ 384	$ 202
Provision	75	39	205
Amounts written off	(17)	(148)	(23)
Balance at end of year	$ 333	$ 275	$ 384