Schedule of Stock Based Compensation by Expense Category (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash compensation expense related to share-based compensation included in operating expense	$ 1,240	$ 1,185	$ 3,256	$ 5,165
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash compensation expense related to share-based compensation included in operating expense	337	249	876	1,011
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total non-cash compensation expense related to share-based compensation included in operating expense	$ 903	$ 936	$ 2,380	$ 4,154