Employee Stock Ownership Plans - Summary of Stock Based Compensation Included in Cost of Sales or Operating Expenses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components Of Other Operating Cost And Expense Line Items
Total stock-based compensation	$ 8,781	$ 4,426	$ 1,654
Cost of Product Revenue [Member]
Components Of Other Operating Cost And Expense Line Items
Total stock-based compensation	1,121	496	221
Research and Development Expenses [Member]
Components Of Other Operating Cost And Expense Line Items
Total stock-based compensation	1,046	267	112
Sales and Marketing Expenses [Member]
Components Of Other Operating Cost And Expense Line Items
Total stock-based compensation	1,390	727	384
General and Administrative Expenses [Member]
Components Of Other Operating Cost And Expense Line Items
Total stock-based compensation	$ 5,224	$ 2,936	$ 937