Research and License Agreements - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Aug. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) LicenseAgreement shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)
Series B Convertible Preferred Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Convertible preferred stock, shares issued | shares		0	4,999,976
Series A Convertible Preferred Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Convertible preferred stock, shares issued | shares		0	2,172,520
Contract Research Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Convertible preferred stock, shares issued | shares		0
Contract Research Agreement | Series B Convertible Preferred Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Convertible preferred stock, shares issued | shares			70,028
Convertible preferred stock, fair values			$ 1,100,000
Contract Research Agreement | Series A Convertible Preferred Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Convertible preferred stock, shares issued | shares				133,000
Convertible preferred stock, fair values				$ 845,000
University Research Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research agreement date		2013-12
Maximum allowable research and development expenses per year		$ 1,800,000			$ 386,000
Research agreement expiration date		Aug. 31, 2017
Increasing the maximum research expenditure limit	$ 750,000
Payments pursuant to research agreements	$ 375,000	$ 832,000	563,000	386,000
License Agreements
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research agreement date		2013-12
Annual license fees paid		$ 5,000	$ 0	$ 0
Number of license agreements | LicenseAgreement		2