Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reserves for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance Beginning of Year	$ 31	$ 34	$ 45
Charged to Income	36	42	39
Accounts Written Off/Use of Reserve	(42)	(45)	(50)
Balance End of Year	25	31	34
Merger and Restructuring Accruals [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance Beginning of Year	45	14	32
Charged to Income	15	82	18
Accounts Written Off/Use of Reserve	(47)	(51)	(36)
Balance End of Year	$ 13	$ 45	$ 14