Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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No definition available.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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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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- Definition

Gross number of share options (or share units) granted during the period.

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No definition available.

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Percentage of vesting of award under share-based payment arrangement.

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- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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No definition available.

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The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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No definition available.

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Number of shares that have been repurchased and retired during the period.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Stockholders' Equity - Stock incentive plan (Details) - $ / shares	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2014	Jul. 28, 2004
Stockholders Equity
Maximum number of shares authorized for grant			2,000,000
Options granted (in shares)	141,000	158,000
Number of shares available for granting options or stock awards	1,073,000
Share Repurchase Authorization 2004
Stockholders Equity
Number of shares of common stock authorized to be repurchased				2,000,000
Number of shares purchased	0	0
Remaining number of shares authorized to be repurchased	384,809
Restricted Stock
Stockholders Equity
Average purchase price of shares purchased and retired (in dollars per share)	$ 2.27	$ 1.86
Vesting rights percentage each year beginning on the second anniversary date of the grant			20.00%
Service period over which the aggregate market value of stock is being amortized			6 years
Number of shares purchased and retired	51,791	50,572