Preferred Stock, Common Stock and Stockholders' Equity - Initial Public Offering - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	12 Months Ended		0 Months Ended
	Oct. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2013
Sale Of Stock [Line Items]
Warrants to purchase common stock				22,000
Warrant exercise price per share		$ 16.73	18.20
Date warrants are exercisable		Sep. 24, 2014
Expiration date of warrants		Sep. 24, 2018
Warrants to purchase convertible preferred stock				110,000
Underwriter discounts, commissions and other offering expenses	$ 3.9
Net proceeds from issuance from IPO	$ 25.1
Common Stock [Member]
Sale Of Stock [Line Items]
Conversion of shares of preferred stock to common stock, Shares			2,439,002
Initial Public Offering [Member]
Sale Of Stock [Line Items]
Shares issued, price per share				12.00
Warrants to purchase common stock				84,000
Warrant exercise price per share				21.00
Initial Public Offering [Member] | Common Stock [Member]
Sale Of Stock [Line Items]
Common stock, shares issued				2,100,000
Conversion of shares of preferred stock to common stock, Shares				2,439,002
Over-Allotment Option [Member]
Sale Of Stock [Line Items]
Shares issued, price per share	$ 12.00
Over-Allotment Option [Member] | Common Stock [Member]
Sale Of Stock [Line Items]
Common stock, shares issued	315,000