Stock Plans (Details Textual) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($) share_based_compensation_plan shares	Mar. 31, 2017 USD ($) shares
Stock Plans (Textual) [Abstract]
Stock-based compensation plans (in shares) \| share_based_compensation_plan	2
Stock options granted during the period (in shares) \| shares	0	0
Stock-based compensation expense	$ 2,624	$ 1,538
Bonuses settled in stock
Stock Plans (Textual) [Abstract]
Stock compensation expense	900	500
Bonuses settled in stock \| Director
Stock Plans (Textual) [Abstract]
Settled bonuses, previously earned under plan	$ 203
Number shares of fully vested common stock and restricted stock units \| shares	34,376
Stock compensation expense	$ 109
Bonuses settled in stock \| Annual Incentive Bonuses, 2017 Performance Period [Member]
Stock Plans (Textual) [Abstract]
Settled bonuses, previously earned under plan	3,000
Bonuses settled in stock \| Annual Incentive Bonuses, 2016 Performance Period
Stock Plans (Textual) [Abstract]
Settled bonuses, previously earned under plan	300	1,200
Stock options
Stock Plans (Textual) [Abstract]
Stock-based compensation expense	72	51
Restricted stock awards
Stock Plans (Textual) [Abstract]
Stock-based compensation expense	$ 60	97
Director restricted stock unit awards
Stock Plans (Textual) [Abstract]
Restricted stock unit vesting period (in years)	1 year
Restricted stock unit awards
Stock Plans (Textual) [Abstract]
Stock-based compensation expense	$ 1,502	$ 865
Restricted stock unit vesting period (in years)	4 years
Number of unrestricted shares of common stock to be received upon vesting \| shares	1
Restricted stock unit awards \| Bonuses settled in stock \| Annual Incentive Bonuses, 2016 Performance Period
Stock Plans (Textual) [Abstract]
Number shares of fully vested common stock and restricted stock units \| shares	42,662	89,730
Restricted stock unit awards \| Service-based
Stock Plans (Textual) [Abstract]
Stock-based compensation expense	$ 1,084	$ 667
Market condition restricted stock units \| Minimum
Stock Plans (Textual) [Abstract]
Potential vesting percentages	0.00%
Market condition restricted stock units \| Maximum
Stock Plans (Textual) [Abstract]
Potential vesting percentages	200.00%
Market condition restricted stock units \| Performance period one
Stock Plans (Textual) [Abstract]
Restricted stock unit vesting period (in years)	1 year
Market condition restricted stock units \| Performance period two
Stock Plans (Textual) [Abstract]
Restricted stock unit vesting period (in years)	2 years
Market condition restricted stock units \| Performance period three
Stock Plans (Textual) [Abstract]
Restricted stock unit vesting period (in years)	3 years
Employee stock purchase plan
Stock Plans (Textual) [Abstract]
Stock-based compensation expense	$ 29	$ 34
Discount rate from market value on offering date	85.00%
Offering period	6 months
Fully vested common stock \| Bonuses settled in stock \| Annual Incentive Bonuses, 2017 Performance Period [Member]
Stock Plans (Textual) [Abstract]
Number shares of fully vested common stock and restricted stock units \| shares	506,017
Fully vested common stock \| Bonuses settled in stock \| Annual Incentive Bonuses, 2016 Performance Period
Stock Plans (Textual) [Abstract]
Number shares of fully vested common stock and restricted stock units \| shares		142,582

Number of active stock based compensation plans.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares

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- Definition

Stock plans.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
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The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

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The total fair value of shares issued during the period under a deferred compensation arrangement.

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Number of shares issued pursuant to the terms of a deferred compensation arrangement.

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

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

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