Common Stock and Preferred Stock - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 Vote $ / shares shares	Dec. 31, 2016 shares
Equity [Abstract]
Each share of common stock is entitled to vote | Vote	1
Preferred stock, shares authorized (in shares)	15,000,000	15,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0
Preferred stock warrants were converted into warrants to purchase common stock (in shares)	355,585
Exercise price of common stock warrants (in dollars per share) | $ / shares	$ 10.96