Stock-based Compensation - Stock Options Vested and Expected to Vest (Details) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Options [Roll Forward]
Balance as of December 31, 2018	137,547	100,870
Vested and expected to vest at December 31, 2018	122,637
Exercisable at December 31, 2018	64,836
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2018 (in dollars per share)	$ 80.07
Vested and expected to vest at December 31, 2018	88.94
Exercisable at December 31, 2018	$ 161.99
Weighted Average Remaining Contractual Term [Roll Forward]
Balance as of December 31, 2018	7 years 10 months 24 days
Vested and expected to vest at December 31, 2018	7 years 9 months 10 days
Exercisable at December 31, 2018	6 years 7 months 2 days

No definition available.

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- Definition

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.

+ References

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-Publisher FASB
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-SubTopic 10
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- Definition

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.

+ References

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- Definition

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

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- Definition

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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No definition available.

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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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- Definition

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 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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