Employee Stock Purchase Plan (Details) - USD ($)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	4,900,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee subscription rate	15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee	2,500
Maximum employee subscription	$ 25,000
Purchase price of common stock, percent	85.00%
Shares available for grant	3,500,000
Issuance of common stock under Employee Stock Purchase Plan (Shares)	313,773	464,757	314,868
Proceeds from issuance of shares under incentive and share-based compensation plans, excluding stock options	$ 2,600,000	$ 1,500,000	$ 3,200,000
Risk free interest rate	0.80%	0.80%	2.30%
Dividend yield	0.30%	0.70%	0.70%
Volatility factor of the expected market price of the Company's common stock	106.10%	166.20%	56.60%
Expected life (in years)	6 months	6 months	6 months
Stock-based compensation expense	$ 1,400,000	$ 900,000	$ 1,100,000

Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription

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

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Amount of cash inflow from issuance of shares under share-based payment arrangement. Excludes option exercised.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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The highest quantity of shares an employee can purchase under the plan per period.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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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Purchase price of common stock expressed as a percentage of its fair value.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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