Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Provision for income taxes	$ 23,533,000	$ 23,074,000	$ 45,386,000	$ 45,483,000
Effective tax rate	30.20%	31.50%	29.90%	31.70%
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	$ 1,800,000		$ 1,800,000