Summary of Status of Stock Options Under Twenty Twelve Plan and Twenty Zero Two Plan (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares
Granted (in shares)	633,224
Exercised (in shares)	(4,156,728)	(1,721,282)	(2,515,769)
Stock options under the Plan, the 2002 Plan, and the 1992 Plan
Shares
Options Outstanding, at beginning of the year (in shares)	8,271,270
Granted (in shares)	633,224
Exercised (in shares)	(4,156,728)
Forfeited, Expired or Cancelled (in shares)	(43,997)
Options Outstanding, at the end of year (in shares)	4,703,769	8,271,270
Options Exercisable at the end of year (in shares)	3,444,609
Weighted average exercise price per share
Options Outstanding, Beginning Balance (in dollars per share)	$ 55.51
Granted (in dollars per share)	58.25
Exercised (in dollars per share)	56.24
Forfeited, Expired or Cancelled (in dollars per share)	59.99
Options Outstanding, Ending Balance (in dollars per share)	55.20	$ 55.51
Options Exercisable, at the end of the year (in dollars per share)	$ 52.96
Weighted average remaining contractual term (years)
Options Outstanding, at the end of the year	5 years 3 months 18 days
Options Exercisable, at the end of the year	4 years 1 month 6 days
Aggregate intrinsic value
Options Outstanding, at the end of year	$ 158.2
Options Exercisable at end of the year	$ 123.5