Employee Stock And Savings Plans - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Defined Contribution Pension	Dec. 31, 2011 Defined Contribution Pension	Dec. 31, 2010 Defined Contribution Pension	Dec. 31, 2012 Stock Options Y	Dec. 31, 2012 Employee Stock Purchase Plan	Dec. 31, 2011 Employee Stock Purchase Plan	Dec. 31, 2010 Employee Stock Purchase Plan	Jan. 01, 2013 Employee Stock Purchase Plan Share Based Awards
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)							3 years
Expiration of awards, years after date of awards							10
Employee purchase percentage of the closing price of common stock								85.00%
Compensation cost recognized relative to stock price								15.00%
Share-based compensation	$ 44	$ 39	$ 39
Income tax benefits from share-based compensation	15	14	13
Unrecognized compensation cost	53
Period over which unrecognized cost will be recognized, years	2 years 3 months 18 days
Weighted-average estimated fair value per share of stock options granted	$ 21.71	$ 22.68	$ 17.46
Shares available for grant							2.8				2.8
Shares issued under equity plan								0.4	0.5	0.5
Defined contribution plan expense				$ 33	$ 38	$ 29