Recorded Share-Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Component of Operating Other Cost and Expense [Line Items]
Share-based compensation expense	$ 5,751	$ 3,708	$ 16,111	$ 10,871
Research and development
Component of Operating Other Cost and Expense [Line Items]
Share-based compensation expense	1,216	904	3,450	2,890
Selling, general and administrative
Component of Operating Other Cost and Expense [Line Items]
Share-based compensation expense	$ 4,535	$ 2,804	$ 12,661	$ 7,981