Share Based Payments - Recognized Stock-Based Compensation Expense on all Stock Option Awards (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total operating expenses	$ 3,181	$ 1,716
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total operating expenses	1,467	664
Selling, general and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total operating expenses	$ 1,714	$ 1,052