Investments - Summarized Financial Assets Measured at Fair Value on Recurring Basis (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	$ 37,548	$ 42,525
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	21,672	21,963
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	15,875	20,562
Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Cash Equivalents	21,672	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	21,672	21,963
FDIC Guaranteed Certificates of Deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	3,079	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	3,079	2,118
Corporate Notes/Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sales securities - current	12,797	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	$ 12,797	$ 18,444