STOCK COMPENSATION EXPENSE (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expenses	$ 5,869	$ 2,042	$ 13,595	$ 5,294
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocation of stock-based compensation expense	1,662	794	4,381	2,021
Selling, General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocation of stock-based compensation expense	4,207	1,248	9,214	3,273
Equity Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expenses	5,782	1,952	13,374	5,117
Employee Stock Purchase Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation expenses	$ 87	$ 90	$ 221	$ 177