Stock Plans Stock Plans (Schedule of RSU Expense by Vesting Type) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,459	$ 1,011	$ 2,662	$ 1,850
Restricted stock unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	745	370	1,481	674
Restricted stock unit awards | Service-based
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	536	363	1,069	575
Performance restricted stock unit awards | Performance-based objectives
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	29	(27)	41	32
Performance restricted stock unit awards | Market-condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 180	$ 34	$ 371	$ 67