Fair Value Measurements - Valuation of Company's Assets and Liabilities Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	$ 62,126	$ 90,536
Securities available-for-sale	64,863	67,742
Assets Fair Value Total	127,092	157,806
Municipal Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	11,696	16,052
Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	53,167	51,690
Foreign Exchange Contract [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	103	(472)
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	62,126	90,536
Assets Fair Value Total	62,126	90,536
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Fair Value Total	64,966	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	11,696	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	53,167	51,690
Level 2 [Member] | Foreign Exchange Contract [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	$ 103	$ (472)