Schedule of Stock Based Compensation by Expense Category (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
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			$ 3,980	$ 3,546
2012 Incentive Plan
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	2,762	1,878	3,980	3,546
2012 Incentive Plan | 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	507	383	758	726
2012 Incentive Plan | 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	$ 2,255	$ 1,495	$ 3,222	$ 2,820