Total Compensation Cost from Share-Based Payments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 14,317	$ 3,531	$ 19,928	$ 8,444
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	5,762	1,675	8,416	4,191
Selling, General and Administrative Expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	8,555	1,856	11,512	4,253
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	4,751	1,803	8,112	4,692
Stock and Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	9,445	1,671	11,592	3,646
Purchases of common stock at a discount
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 121	$ 57	$ 224	$ 106