Total Compensation Cost from Share-Based Payments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 8,449	$ 14,317	$ 16,945	$ 19,928
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	3,633	5,762	7,341	8,416
Selling, general and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	4,816	8,555	9,604	11,512
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	4,164	4,751	8,844	8,112
Stock and stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	4,178	9,445	7,826	11,592
Purchases of common stock at a discount
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 107	$ 121	$ 275	$ 224