Stock Compensation Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expenses	$ 1,524,000	$ 748,000	$ 4,353,000	$ 2,776,000
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocation of stock-based compensation expense	798,000	198,000	1,306,000	576,000
Selling, General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocation of stock-based compensation expense	726,000	550,000	3,047,000	2,145,000
Restructuring Charges
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocation of stock-based compensation expense				55,000
1995 Equity Incentive Plan (the Equity Plan)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expenses	1,410,000	733,000	4,188,000	2,744,000
Employee Stock Purchase Plans
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expenses	$ 114,000	$ 15,000	$ 165,000	$ 32,000