Summary of Restructuring Costs by Function (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Restructuring Cost And Reserve [Line Items]
Total restructuring costs, Cash	$ 388
Total restructuring costs, Non-cash	145	[1]
Total restructuring costs	533
Research and Development [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs, Cash	357
Total restructuring costs, Non-cash	145	[1]
Total restructuring costs	502
General and Administration [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring costs, Cash	31
Total restructuring costs	$ 31

[1] The non-cash restructuring expense relates to acceleration of stock options.