Formation and Business of the Company - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	1 Months Ended
	Mar. 31, 2015	Jan. 31, 2015
Public Offering [Line Items]
Business incorporated date	Dec. 10, 2008
Proceeds from issuance of common stock in secondary offering, net of issuance costs	$ 80,208
Secondary Offering [Member]
Public Offering [Line Items]
Secondary public offering shares of common stock issued		4,999,999
Proceeds from issuance of common stock in secondary offering, net of issuance costs		$ 80,200