Stock-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock options, expense	$ 16	$ 16	$ 22
Restricted stock awards, expense	66	51	41
Total stock-based compensation expense	82	67	63
Tax benefit recognized	(30)	(25)	(23)
Stock-based compensation expense, net of tax	$ 52	$ 42	$ 40