Formation and Business of the Company - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended	73 Months Ended
Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Initial Public Offering [Line Items]
Business incorporated date		Dec. 10, 2008
Proceeds from issuance of common stock in initial public offering, net of issuance costs	$ 132,100	$ 132,137	$ 132,137
Common stock, shares authorized	50,000,000us-gaap_CommonStockSharesAuthorized	50,000,000us-gaap_CommonStockSharesAuthorized	50,000,000us-gaap_CommonStockSharesAuthorized	15,652,174us-gaap_CommonStockSharesAuthorized
Convertible preferred stock, shares authorized	5,000,000us-gaap_TemporaryEquitySharesAuthorized	5,000,000us-gaap_TemporaryEquitySharesAuthorized	5,000,000us-gaap_TemporaryEquitySharesAuthorized	135,816,462us-gaap_TemporaryEquitySharesAuthorized
IPO [Member]
Initial Public Offering [Line Items]
Initial public offering shares of common stock issued	6,900,000

- Definition

The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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