Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued clinical and preclinical costs	$ 10,033	$ 9,587
Accrued employee compensation costs	8,748	8,189
Accrued contract manufacturing costs	4,673	4,830
Accrued professional fees	2,799	4,258
Accrued research costs	1,186	629
Other	3,577	1,560
Total accrued expenses	$ 31,016	$ 29,053