Summary of Status of Stock Options Under Twenty Twelve Plan and Twenty Zero Two Plan (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Shares
Granted	386,749
Exercised	(2,515,769)	(3,088,490)	(973,270)
Stock options under the Plan, the 2002 Plan, and the 1992 Plan
Shares
Options Outstanding, at beginning of the year	11,992,811
Granted	386,749
Exercised	(2,515,769)
Forfeited, Expired or Cancelled	(192,710)
Options Outstanding, at the end of year	9,671,081
Options Exercisable at the end of year	7,642,521
Weighted average exercise price per share
Options Outstanding, Beginning Balance	53.64
Granted	60.85
Exercised	50.70
Forfeited, Expired or Cancelled	53.54
Options Outstanding, Ending Balance	54.70
Options Exercisable, at the end of the year	55.82
Weighted average remaining contractual term (years)
Options Outstanding, at the end of the year	5 years 1 month 6 days
Options Exercisable, at the end of the year	4 years 6 months
Aggregate intrinsic value
Options Outstanding, at the end of year	132.6
Options Exercisable at end of the year	96.9