The Company - Additional Information (Detail)			1 Months Ended	3 Months Ended		12 Months Ended
	Nov. 03, 2014 USD ($)	Sep. 30, 2014 USD ($)	Oct. 31, 2013 USD ($) $ / shares shares	Mar. 31, 2016 USD ($) Segment shares	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) shares
Organization And Nature Of Business [Line Items]
Number of operating segments | Segment				1
Common stock initial public offering (in shares) | shares			7,728,000
Net proceeds from initial public offering			$ 68,300,000
Proceeds from sale of common stock				$ 0	$ 35,000,000
Sale of stock, commissions, percentage of gross sales (up to)						3.00%
Convertible notes
Organization And Nature Of Business [Line Items]
Gross proceeds		$ 125,000,000
Proceeds from issuance of convertible notes, net of discounts		$ 122,900,000
IPO
Organization And Nature Of Business [Line Items]
Public offering price of the shares sold (in USD per share) | $ / shares			$ 10.00
Maximum
Organization And Nature Of Business [Line Items]
Shelf registration statement, aggregate dollar amount	$ 150,000,000.0
Common stock
Organization And Nature Of Business [Line Items]
Shelf registration, amount available for issuance				$ 48,100,000
Cantor Fitzgerald and Co. | Common stock
Organization And Nature Of Business [Line Items]
Common stock issued and sold under sales agreement (in shares) | shares				0		1,754,556
Proceeds from sale of common stock						$ 50,500,000
Cantor Fitzgerald and Co. | Common stock | Maximum
Organization And Nature Of Business [Line Items]
Shelf registration statement, aggregate dollar amount	$ 50,000,000