Fair Value of Financial Instruments - Summary of Company's Financial Assets Carried at Fair Value (Detail) (Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 27,504	$ 28,210
Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	5,021	5,001
U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term marketable securities - U.S. government agency securities	100,170	100,299
Quoted Prices in Active Markets for Identical Items (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	27,504	28,210
Quoted Prices in Active Markets for Identical Items (Level 1) [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term marketable securities - U.S. government agency securities	95,168	75,288
Significant Other Observable Inputs (Level 2) [Member] | Bank Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	5,021	5,001
Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term marketable securities - U.S. government agency securities	$ 5,002	$ 25,011