Stock-based Compensation - Expense Related to Stock Options (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to stock options	$ 342	$ 819	$ 616	$ 1,115
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to stock options	86	62	156	114
Selling, general and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to stock options	256	689	460	900
Discontinued operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to stock options	$ 0	$ 68	$ 0	$ 101