Stock-Based Compensation - Weighted average assumptions (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Stock-based compensation fair value assumptions
Weighted average fair value of options granted	$ 4.90	$ 5.49
Proceeds from exercise of stock options	$ 128
Forfeited		2,787
Employee stock option
Stock-based compensation fair value assumptions
Expected dividends	0.00%	0.00%
Expected life	5 years 9 months	5 years 9 months
Total stock compensation cost	$ 272	$ 293
Tax benefits recognized related to stock compensation cost	0
Unrecognized compensation cost	$ 350
Weighted average period in which the unrecognized compensation cost will be recognized	1 year 1 month 21 days
Employee stock option \| Minimum
Stock-based compensation fair value assumptions
Risk-free rate	1.95%	2.84%
Expected volatility	22.44%	19.68%
Weighted average fair value of options granted	$ 4.84	$ 4.87
Employee stock option \| Maximum
Stock-based compensation fair value assumptions
Risk-free rate	2.61%	3.06%
Expected volatility	22.48%	26.11%
Weighted average fair value of options granted	$ 5.30	$ 5.52

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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 tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of cash inflow from exercise of option under 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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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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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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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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