Changes in Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Number of Shares
Exercised	(615,674)	(1,495,926)	(548,659)
Outstanding at end of year	5,434,228
Exercisable at end of year	2,319,735
Stock Options
Number of Shares
Outstanding at beginning of year	5,302,384	5,431,560	5,399,060
Granted at FMV	1,397,312	1,605,628	1,057,000
Exercised	(974,500)	(1,580,950)	(560,500)
Forfeited	(290,968)	(153,854)	(464,000)
Outstanding at end of year	5,434,228	5,302,384	5,431,560
Exercisable at end of year	2,319,735	2,499,610	3,506,310
Average Exercise Price
Outstanding at beginning of year	48.83	42.01	40.90
Granted at FMV	67.64	52.85	43.95
Exercised	39.30	29.04	19.58
Forfeited	52.73	53.33	60.65
Outstanding at end of year	55.17	48.83	42.01
Exercisable at end of year	51.14	45.07	34.86