Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 22,812,000	$ 20,057,000	$ 72,774,000	$ 65,443,000
Effective tax rate	26.30%	28.60%	27.90%	29.50%
Reasonably possible change in unrecognized tax benefits over next 12 months, lower range	0		0
Reasonably possible change in unrecognized tax benefits over next 12 months, upper range	$ 1,500,000		$ 1,500,000