v3.10.0.1

Stock Awards - Estimates and assumptions (Details) - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Estimates and assumptions used
Fair value of common stock, minimum	$ 11.95	$ 22.87	$ 4.47
Fair value of common stock, maximum	$ 11.95	$ 30.35	$ 11.95
Risk-free interest rate, minimum	1.90%	2.40%	1.80%
Risk-free interest rate, maximum	2.00%	2.70%	2.10%
Expected life	6 years 4 months 24 days	5 years 10 months 24 days	6 years 2 months 12 days
Expected dividend yield		0.00%
Expected volatility, minimum	46.50%	50.10%	46.50%
Expected volatility, maximum	52.60%	50.60%	54.00%
Weighted average grant date fair value of the options granted	$ 6.26	$ 13.38	$ 5.06

Minimum price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

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- Definition

Maximum price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

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- References

No definition available.

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- Definition

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.

+ References

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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.

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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.

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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.

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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.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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