Stock Options Status and Activity (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, January 1, 2013	2,654,247	2,447,475	2,447,475
Granted	388	311,539
Canceled		(7,225)
Forfeited	(450)	(14,920)
Exercised	(393,442)	(82,622)
Outstanding, March 31, 2013	2,260,743	2,654,247	2,260,743	2,447,475
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, January 1, 2013	$ 22.12	$ 20.14	$ 20.14
Granted	$ 38.90	$ 36.29
Canceled		$ 11.73
Forfeited	$ 21.81	$ 14.59
Exercised	$ 22.53	$ 19.96
Outstanding, March 31, 2013	$ 22.06	$ 22.12	$ 22.06	$ 20.14
Weighted Avg. Remaining Life in Years		4 years 3 months 0 days	4 years 8 months 12 days	4 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 41	$ 29	$ 29
Aggregate Intrinsic Value, Exercised	7	1
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 44	$ 41	$ 44	$ 29