Stock-Based Compensation (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation [Abstract]
Share-based compensation expense	$ 762	$ 1,030	$ 1,447	$ 2,058
Employee Stock Purchase Plans [Abstract]
Expected life			6 months
Stock Options [Member]
Assumptions for Black-Scholes Option Pricing Model [Abstract]
Dividend yield	0.00%	0.00%	0.00%	0.00%
Expected volatility	66.40%	55.70%	66.40%	55.90%
Risk-free interest rate	2.18%	2.56%	2.18%	2.54%
Expected life of options (in years)	4 years	4 years	4 years	4 years
Share-based Payment Award [Abstract]
Options exercised (in shares)	0	0	0	0
Unrecognized compensation cost related to options	$ 555		$ 555
Share-based compensation, weighted average recognized period			1 year 10 months 24 days
RSUs [Member]
Share-based Payment Award [Abstract]
Share-based compensation, weighted average recognized period			2 years 7 months 6 days
Unrecognized compensation cost related to RSUs	$ 4,960		$ 4,960

The expected life of employee stock purchase plans.

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Weighted-average period over which cost not yet recognized is expected to be recognized for 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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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Amount of noncash expense for share-based payment arrangement.

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

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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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Number of share options (or share units) exercised during the current period.

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