Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued clinical and preclinical costs	$ 10,170	$ 9,587
Accrued contract manufacturing costs	5,161	4,830
Accrued employee compensation costs	4,553	8,189
Accrued professional fees	2,957	4,258
Accrued research costs	663	629
Accrued facility-related costs	51	127
Other	722	1,433
Total accrued expenses	$ 24,277	$ 29,053