Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reserves for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance Beginning of Year	$ 25	$ 31	$ 34
Charged to Income	42	36	42
Accounts Written Off/Use of Reserve	(43)	(42)	(45)
Balance End of Year	24	25	31
Merger and Restructuring Accruals [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance Beginning of Year	13	45	14
Charged to Income	4	15	82
Accounts Written Off/Use of Reserve	(10)	(47)	(51)
Balance End of Year	$ 7	$ 13	$ 45