Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Provision for income taxes	$ 20,057,000	$ 14,765,000	$ 65,443,000	$ 60,248,000
Effective tax rate	28.60%	23.40%	29.50%	29.10%
Minimum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Change in unrecognized tax benefits over next 12 months	0		0
Maximum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Change in unrecognized tax benefits over next 12 months	$ 1,700,000		$ 1,700,000