Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended				12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Benefit [Line Items]
Income tax provision	$ (246,000)	$ (282,000)	$ (382,000)	$ (102,000)	$ 0	$ (1,012,000)
Consideration received under collaboration agreement						2,600,000
Income tax provision within equity						1,000,000
Net operating loss carryforwards, federal					35,800,000
Net operating loss carryforwards, state					$ 31,500,000
Net operating loss carryforwards, expiration year					2034
Net operating loss carryforwards, expiration date description					Begin to expire in 2034
Research and development tax credit	$ 418,000				$ 1,873,000	418,000
Research and development tax credits, expiration date description					Begin to expire in 2034 and 2029
Increase in valuation allowance					$ 13,100,000	3,800,000	$ 3,600,000
Unrecognized tax benefits					0
Federal [Member]
Income Tax Benefit [Line Items]
Research and development tax credit					$ 1,200,000
Research and development tax credits, expiration year					2034
State [Member]
Income Tax Benefit [Line Items]
Research and development tax credit					$ 800,000
Research and development tax credits, expiration year					2029
Novartis [Member]
Income Tax Benefit [Line Items]
Total fixed amount of consideration under collaboration agreement						$ 30,000,000