Summary of Restructuring Costs by Function (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016		Jun. 30, 2016
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	$ 536		$ 924
Total restructuring expenses, Non-cash	90	[1]	235	[2]
Total restructuring expenses	626		1,159
Research and Development [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	463		820
Total restructuring expenses, Non-cash	48	[1]	193	[2]
Total restructuring expenses	511		1,013
General and Administration [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	73		104
Total restructuring expenses, Non-cash	42	[1]	42	[2]
Total restructuring expenses	$ 115		$ 146

[1] The non-cash restructuring expense relates to accelerated depreciation for certain assets.

[2] The non-cash restructuring expense relates to acceleration of stock option vesting and accelerated depreciation for certain assets.