Stock Incentive and Employee Stock Purchase Plans - Summary of Share-Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Amounts for share-based compensation awards	$ 3,588	$ 3,443	$ 7,500
Cost of revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Amounts for share-based compensation awards	5	84	747
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Amounts for share-based compensation awards	654	1,114	3,042
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Amounts for share-based compensation awards	247	669	1,403
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Amounts for share-based compensation awards	$ 2,682	$ 1,576	$ 2,308