Additional Information about Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding at end of year	5,907,359
Options Outstanding, Avg. Life in Years	4 years
Options Outstanding, Aggregate Intrinsic Value	$ 28,025,000
Exercisable at end of year	2,474,636
Options Exercisable,Avg. Life in year	2 years 2 months 12 days
Options Exercisable, Aggregate Intrinsic Value	21,042,000
Range of Exercise Prices per Option $ 21.17 to $ 23.58
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit	$ 21.17
Range of exercise prices, upper limit	$ 23.58
Outstanding at end of year	70,750
Options Outstanding, Avg. Life in Years	1 month 6 days
Options Outstanding, Aggregate Intrinsic Value	2,614,000
Exercisable at end of year	70,750
Options Exercisable,Avg. Life in year	1 month 6 days
Options Exercisable, Aggregate Intrinsic Value	2,614,000
Range of Exercise Prices per Option $ 30.30 to $ 45.70
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit	$ 30.30
Range of exercise prices, upper limit	$ 45.70
Outstanding at end of year	924,910
Options Outstanding, Avg. Life in Years	3 years 6 months
Options Outstanding, Aggregate Intrinsic Value	14,327,000
Exercisable at end of year	697,410
Options Exercisable,Avg. Life in year	2 years 7 months 6 days
Options Exercisable, Aggregate Intrinsic Value	11,176,000
Range of Exercise Prices per Option $ 51.07 to $ 57.32
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit	$ 51.07
Range of exercise prices, upper limit	$ 57.32
Outstanding at end of year	1,643,097
Options Outstanding, Avg. Life in Years	2 years 10 months 24 days
Options Outstanding, Aggregate Intrinsic Value	11,084,000
Exercisable at end of year	1,071,476
Options Exercisable,Avg. Life in year	2 years 3 months 18 days
Options Exercisable, Aggregate Intrinsic Value	7,252,000
Range of Exercise Prices per Option $ 59.66 to $ 72.75
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of exercise prices, lower limit	$ 59.66
Range of exercise prices, upper limit	$ 72.75
Outstanding at end of year	3,268,602
Options Outstanding, Avg. Life in Years	4 years 10 months 24 days
Options Outstanding, Aggregate Intrinsic Value	0
Exercisable at end of year	635,000
Options Exercisable,Avg. Life in year	1 year 10 months 24 days
Options Exercisable, Aggregate Intrinsic Value	$ 0