Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued employee compensation costs	$ 6,262	$ 6,170
Accrued clinical and preclinical costs	5,972	3,471
Accrued professional fees	3,349	3,403
Accrued contract manufacturing costs	2,145	3,271
Accrued research costs	565	311
Accrued facility-related costs	168	300
Other	1,300	440
Total accrued expenses	$ 19,761	$ 17,366