Income Taxes - Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits, Including Accrued Interest (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Line Items]
Balance beginning	$ 49	$ 53	$ 75
Additions based on tax positions related to the current year	15	9	5
Additions based on tax positions of prior years
Additions due to acquisitions		2
Accrued interest	2	2	3
Reductions for tax positions of prior years	(1)		(1)
Settlements	(4)	(10)	(23)
Lapse of statute of limitations	(7)	(7)	(6)
Balance ending	$ 54	$ 49	$ 53