Stock-Based Compensation - Stock Options Activity (Details) - Common stock options $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance (in shares) \| shares	1,315,360
Granted (in shares) \| shares	2,039,387
Exercised (in shares) \| shares	0
Forfeited (in shares) \| shares	(508,630)
Expired (in shares) \| shares	(504,591)
Outstanding, ending balance (in shares) \| shares	2,341,526
Vested and expected to vest balance (in shares) \| shares	2,081,243
Exercisable balance (in shares) \| shares	482,446
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning balance (in USD per share) \| $ / shares	$ 54.20
Granted (in USD per share) \| $ / shares	6.48
Exercised (in USD per share) \| $ / shares	0.00
Forfeited (in USD per share) \| $ / shares	38.86
Expired (in USD per share) \| $ / shares	81.28
Outstanding, ending balance (in USD per share) \| $ / shares	10.12
Vested and expected to vest balance, weighted average exercise price (USD per share) \| $ / shares	10.53
Exercisable balance, weighted average exercise price (USD per share) \| $ / shares	$ 21.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding balance, weighted average remaining contractual life	8 years 7 months 10 days
Vested and expected to vest balance, weighted average remaining contractual life	8 years 6 months 26 days
Exercisable balance, weighted average remaining contractual life	8 years 26 days
Outstanding balance, aggregate intrinsic value \| $	$ 0
Vested and expected to vest, balance, aggregate intrinsic value \| $	0
Exercisable balance, aggregate intrinsic value \| $	$ 0

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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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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 price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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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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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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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 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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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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

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