Stock Plans (Details Textual) - USD ($) shares in Thousands, $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Weighted-average period for recognizing non-vested stock option | 8 months 12 days | |||
| Employee Stock Option [Member] | ||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
| Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized | $ 0.6 | $ 0.6 | ||
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | 5,000 | 60,000 | 950,000 | 496,000 |