Summary of Restructuring Costs by Function (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016		Sep. 30, 2016
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	$ 995		$ 1,919
Total restructuring expenses, Non-cash	269	[1]	504	[2]
Total restructuring expenses	1,264		2,423
Research and Development [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	628		1,448
Total restructuring expenses, Non-cash	143	[1]	336	[2]
Total restructuring expenses	771		1,784
General and Administration [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses, Cash	367		471
Total restructuring expenses, Non-cash	126	[1]	168	[2]
Total restructuring expenses	$ 493		$ 639

[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.