Total Compensation Cost from Share-Based Payments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 5,610	$ 4,913
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	2,654	2,516
Selling, General and Administrative Expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	2,956	2,397
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	3,360	2,889
Stock and Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	2,147	1,975
Purchases of common stock at a discount
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 103	$ 49