Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) - Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	$ 31,588	$ 42,525
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	18,912	21,963
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	12,676	20,562
Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	18,912	21,963
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	18,912	21,963
FDIC Guaranteed Certificates of Deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	2,882	2,118
FDIC Guaranteed Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	2,882	2,118
Corporate Notes/Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	9,794	18,444
Corporate Notes/Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	$ 9,794	$ 18,444