Stock-Based Compensation - Weighted-Average Fair Value Assumptions (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Jan. 01, 2019
Weighted-Average Assumptions
Weighted-average Black-Scholes fair value per share at date of grant	$ 4.16	$ 5.11
Stock option
Weighted-Average Assumptions
Risk-free interest rate	1.80%	2.70%
Expected term (average in years)	6 years 2 months 12 days	6 years 2 months 12 days
Expected dividend yield	0.00%	0.00%
Expected volatility	55.70%	51.00%
Weighted-average Black-Scholes fair value per share at date of grant	$ 4.16	$ 5.11

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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 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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- Definition

The 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 award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 718
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-Name Accounting Standards Codification
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