Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Number of Options
Outstanding at beginning of year	6,508,833	7,387,753	7,297,399
Granted	1,050,226	1,388,846	1,368,476
Exercised	(963,218)	(2,106,156)	(1,107,063)
Forfeited	(244,378)	(156,269)	(162,470)
Cancelled or expired	(9,126)	(5,341)	(8,589)
Outstanding at end of year	6,342,337	6,508,833	7,387,753
Exercisable at end of year	3,406,594	3,099,479	3,884,494
Available for future grant	4,396,346	2,240,937	3,939,210
Weighted Average Exercise Price per Share
Outstanding at beginning of year	$ 41.86	$ 35.43	$ 30.97
Granted	$ 85.28	$ 54.13	$ 47.39
Exercised	$ 32.41	$ 26.95	$ 19.61
Forfeited	$ 53.49	$ 47.07	$ 42.84
Cancelled or expired	$ 28.93	$ 55.50	$ 53.37
Outstanding at end of year	$ 50.06	$ 41.86	$ 35.43
Exercisable at end of year	$ 40.31	$ 34.49	$ 28.58