Fair Value Measurement - Additional Information (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash balance	$ 47,900,000
Cash equivalents	43,200,000
Short term investments	10,258,000	8,581,000
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 30,500,000	$ 30,400,000