Total Compensation Cost from Share-Based Payments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 9,931	$ 7,638	$ 29,009	$ 24,583
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	3,633	3,229	11,629	10,570
Selling, general and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	6,298	4,409	17,380	14,013
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	187	94	433	369
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	3,348	3,583	11,718	12,427
Stock and stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation cost	$ 6,396	$ 3,961	$ 16,858	$ 11,787