Stock-Based Compensation - Schedule of Stock-Based Compensation Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding beginning balance (in shares)	13,529
Granted (in shares)	5,291
Exercised (in shares)	(150)
Canceled/Forfeited (in shares)	(1,757)
Outstanding ending balance (in shares)	16,913
Exercisable at December 31, 2013 (in shares)	8,829
Vested at December 31, 2013 (in shares)	16,667
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding weighted average exercise price, beginning balance (in usd per share)	$ 2.46
Granted weighted average exercise price (in usd per share)	$ 3.23
Exercised weighted average exercise price (in usd per share)	$ 2.29
Canceled/Forfeited weighted average exercise price (in usd per share)	$ 2.97
Outstanding weighted average exercise price, ending balance (in usd per share)	$ 2.65
Exercisable weighted average exercise price at December 31, 2013 (in usd per share)	$ 2.63
Vested and unvested expected to vest weighted average exercise price at December 31, 2013 (in usd per share)	$ 2.65
Outstanding, weighted average remaining term at December 31, 2013	7 years 8 months 12 days
Exercisable, weighted average remaining term at December 31, 2013	7 years
Vested and unvested expected to vest, weighted average remaining term at December 31, 2013	7 years 8 months 12 days
Outstanding, intrinsic value at December 31, 2013	$ 48
Exercisable, intrinsic value at December 31, 2013	31
Vested and unvested expected to vest, intrinsic value at December 31, 2013	$ 48

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average price of options that were either forfeited or expired.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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