Stock-Based Compensation - Schedule of Fair Value of Employee Stock Options (Details) - Options to Purchase Common Stock	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employees
Share-based Compensation
Expected volatility, Minimum	46.70%	42.60%	44.10%
Expected volatility, Maximum	52.00%	45.30%	48.90%
Risk-free interest rate, Minimum	1.85%	1.12%	1.51%
Risk-free interest rate, Maximum	2.14%	2.26%	1.79%
Dividend yield	0.00%	0.00%	0.00%
Employees \| Minimum
Share-based Compensation
Expected term (in years)	5 years 3 months 18 days	4 years 9 months 18 days	5 years 7 months 6 days
Employees \| Maximum
Share-based Compensation
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Non-Employee
Share-based Compensation
Expected volatility, Minimum	46.70%	52.30%	51.60%
Expected volatility, Maximum	60.50%	52.70%	52.90%
Risk-free interest rate, Minimum	2.09%	1.94%	1.72%
Risk-free interest rate, Maximum	2.44%	2.41%	2.02%
Non-Employee \| Minimum
Share-based Compensation
Expected term (in years)	7 years 2 months 12 days	9 years 6 months	6 years 7 months 6 days
Non-Employee \| Maximum
Share-based Compensation
Expected term (in years)	9 years 7 months 6 days	9 years 9 months 18 days	9 years 1 month 6 days
2016 Employee Stock Purchase Plan
Share-based Compensation
Expected volatility, Minimum	49.30%
Expected volatility, Maximum	72.70%
Risk-free interest rate, Minimum	0.49%
Risk-free interest rate, Maximum	1.02%
2016 Employee Stock Purchase Plan \| Minimum
Share-based Compensation
Expected term (in years)	6 months
2016 Employee Stock Purchase Plan \| Maximum
Share-based Compensation
Expected term (in years)	1 year

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

+ Details

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- Definition

The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

+ Details

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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