Fair Value Measurements - Valuation of Company's Assets and Liabilities Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	$ 80,400	$ 90,536
Securities available-for-sale	65,742	67,742
Foreign currency forward position	(293)	(472)
Assets Fair Value Total	145,849	157,806
Municipal Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	16,594	16,052
Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	49,148	51,690
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	80,400	90,536
Assets Fair Value Total	80,400	90,536
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	(293)	(472)
Assets Fair Value Total	65,449	67,270
Level 2 [Member] | Municipal Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	16,594	16,052
Level 2 [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	$ 49,148	$ 51,690