Stock Based Compensation - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	$ 14,591	$ 19,511	$ 15,527
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	8,031	10,977	8,932
Vesting of Restricted Stock Grants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	2,160	8,534	4,035
Stock Awarded to Directors and Officers
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	4,400		2,560
Cost of Product Sales
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	137
Research and Development Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	2,030	8,573	5,600
Selling, General, and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized	$ 12,424	$ 10,938	$ 9,927