Revenue from Contracts with Customers - Impact of Adoption of Asc 606 on Company's Condensed Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	$ 14,156	$ 11,253	$ 37,611	$ 49,473
Net loss	(6,380)	(11,951)	(26,859)	21,495
Product Sales [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	13,763	8,118	34,367	23,798
Product Royalty Revenues [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	370	1,409	2,197	3,682
Contract Revenues [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	23	$ 1,194	1,047	$ 21,194
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	14,133		37,375
Net loss	(6,403)		(27,096)
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Product Sales [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	13,763		34,367
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Product Royalty Revenues [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	393		2,195
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Contract Revenues [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues			813
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	23		236
Net loss	23		236
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Contract Revenues [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	$ 23		$ 236