Stock-Based Incentive Compensation Plans - Weighted Average Grant Date Fair Value and Assumptions (Details) - $ / shares	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Weighted average grant date fair value per share and fair value assumptions for estimate fair value
Weighted average grant date fair value per share (in dollars per share)	$ 5.43	$ 3.48	$ 9.78	$ 2.47
Stock Options
Weighted average grant date fair value per share and fair value assumptions for estimate fair value
Expected volatility, minimum (percent)	46.62%	41.00%	41.68%	41.00%
Expected volatility, maximum (percent)	47.25%	44.00%	47.25%	46.00%
Risk-free interest rate, minimum (percent)	1.32%	2.74%	1.32%	2.35%
Risk-free interest rate, maximum (percent)	1.39%	2.80%	2.59%	2.93%
Dividend yield (percent)	0.00%	0.00%	0.00%	0.00%
Minimum \| Stock Options
Weighted average grant date fair value per share and fair value assumptions for estimate fair value
Expected term (years)	5 years 8 days	5 years 3 months 17 days	5 years 8 days	5 years
Maximum \| Stock Options
Weighted average grant date fair value per share and fair value assumptions for estimate fair value
Expected term (years)	6 years 11 months 23 days	7 years	7 years	7 years

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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.

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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.

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No definition available.

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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.

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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.

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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.

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