Significant Accounting Polices - Summary of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total stock-based expenses	$ 2,529	$ 2,432	$ 1,260
Research and Development Expense
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total stock-based expenses	1,032	1,069	1,150
General and Administrative Expense
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total stock-based expenses	$ 1,497	$ 1,363	$ 110