Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, 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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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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Gross number of share options (or share units) granted during the period.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the 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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Stock-based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	$ 969,000	$ 668,000	$ 1,205,000
2005 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation shares authorized under stock option plans	770,000
Percent of the fair value options granted	100.00%
Stock options grant and expire	10 years
Stock options granted	0	0
Shares available for grant	0
Weighted average remaining contractual term stock options outstanding	2 years 8 months 15 days
Weighted average remaining contractual life for options exercisable	2 years 8 months 4 days
Unrecognized compensation costs related to unvested stock options	$ 1,691
Unrecognized compensation costs weighted average period	5 months 1 day
2005 Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	5 years
2010 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation shares authorized under stock option plans	90,427			2,500,000	1,350,000
Percent of the fair value options granted	100.00%
Stock options grant and expire	10 years
Stock options granted	0	0
Weighted average remaining contractual term stock options outstanding	2 years 10 months 17 days
Weighted average remaining contractual life for options exercisable	2 years 5 months 23 days
Unrecognized compensation costs related to unvested stock options	$ 3,100,000
Unrecognized compensation costs weighted average period	1 year 9 months
2010 Plan \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	5 years
2010 Plan \| Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years	3 years