Stock Plans (Stock-based Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	$ 9,047	$ 8,239
Less: stock-based compensation expense related to discontinued operations	(31)	(798)
Total stock-based compensation expense, continuing operations	9,078	9,037
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	1,077	948
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	6,635	6,065
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	1,335	1,226
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	271	237
Unvested restricted stock unit awards
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	6,286	5,186
Unvested restricted stock unit awards | Service-based
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	4,054	3,268
Unvested restricted stock unit awards | Performance objectives
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	320	379
Unvested restricted stock unit awards | Market-condition
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	1,912	1,539
Restricted stock units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	83	416
ESPP
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	148	114
Bonuses settled in stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	1,986	2,826
Director fees settled in stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense, including discontinued operations	$ 304	$ 258