Stock Plans (Stock Option Activity) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Number of Shares
Balance at December 31, 2017 | shares	361
Granted | shares	30
Cancelled | shares	(35)
Balance at December 31, 2018 | shares	356
Vested or expected to vest at December 31, 2018 | shares	354
Exercisable at December 31, 2018 | shares	270
Weighted Average Exercise Price
Balance at December 31, 2017 | $ / shares	$ 8.05
Granted | $ / shares	5.37
Cancelled | $ / shares	9.41
Balance at December 31, 2018 | $ / shares	7.69
Vested or expected to vest at December 31, 2018 | $ / shares	7.70
Exercisable at December 31, 2018 | $ / shares	$ 8.20
Additional Disclosures
Balance at period end, Weighted Average Remaining Contractual Term (in years)	5 years 7 months 25 days
Balance at period end, Aggregate Intrinsic Value | $	$ 0
Vested or expected to vest, Weighted Average Contractual Term (in years)	5 years 7 months 19 days
Vested or expected to vest, Aggregate Intrinsic Value | $	$ 0
Exercisable, Weighted Average Contractual Term (in years)	5 years 1 month 5 days
Exercisable, Aggregate Intrinsic Value | $	$ 0