Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued employee compensation costs	$ 4,955	$ 6,170
Accrued clinical and preclinical costs	4,845	3,471
Accrued professional fees	1,924	3,403
Accrued contract manufacturing costs	1,876	3,271
Accrued research costs	579	311
Accrued facility-related costs	270	300
Other	735	440
Total accrued expenses	$ 15,184	$ 17,366