Income Taxes - Income Tax Reconciliation Computed at Federal Statutory Rates to Income Tax Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Provision for income taxes at statutory rate	$ 16,782	$ 15,462	$ 12,117
State and local income taxes, net of federal tax benefit	791	429	343
Foreign rate differential	(150)	(220)	(171)
Effect of rate changes on deferred taxes	110	232	(76)
Stock compensation	60	113	68
Research credits	(535)		(212)
Reversal of reserve for income taxes	(86)	(361)	(111)
Other, net	(109)	(440)	(7)
Reported income tax provision	$ 16,863	$ 15,215	$ 11,951
Provision for income taxes at statutory rate, tax rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal tax benefit, tax rate	1.70%	1.00%	1.00%
Foreign rate differential, tax rate	(0.30%)	(0.50%)	(0.50%)
Effect of rate changes on deferred taxes, tax rate	0.20%	0.50%	(0.20%)
Stock compensation, tax rate	0.10%	0.20%	0.20%
Research credits, tax rate	(1.10%)		(0.60%)
Reversal of reserve for income taxes, tax rate	(0.20%)	(0.80%)	(0.40%)
Other, net, tax rate	(0.20%)	(1.00%)	0.00%
Reported income tax provision, tax rate	35.20%	34.40%	34.50%