Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common stock
Par value per share (in USD per share)	$ 0.001	$ 0.001	$ 0.001
Shares authorized (in shares)	100,000,000us-gaap_CommonStockSharesAuthorized	15,045,871us-gaap_CommonStockSharesAuthorized	7,804,281us-gaap_CommonStockSharesAuthorized
Shares issued (in shares)	16,878,817us-gaap_CommonStockSharesIssued	369,460us-gaap_CommonStockSharesIssued	360,961us-gaap_CommonStockSharesIssued
Shares outstanding (in shares)	16,878,817us-gaap_CommonStockSharesOutstanding	369,460us-gaap_CommonStockSharesOutstanding	360,961us-gaap_CommonStockSharesOutstanding
Convertible preferred stock
Par value per share (in USD per share)	$ 0.001	$ 0.001	$ 0.001
Shares authorized	10,000,000us-gaap_TemporaryEquitySharesAuthorized	12,882,593us-gaap_TemporaryEquitySharesAuthorized	5,969,418us-gaap_TemporaryEquitySharesAuthorized
Shares issued	0us-gaap_TemporaryEquitySharesIssued	9,769,422us-gaap_TemporaryEquitySharesIssued	5,818,356us-gaap_TemporaryEquitySharesIssued
Shares outstanding	0	9,769,422	5,818,356
Liquidation preference	$ 0	$ 84,300	$ 52,000

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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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The aggregate liquidation preference (or restrictions) of stock classified as temporary equity that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. 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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Per share amount of par value or stated value of stock classified as temporary equity. 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.

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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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