Stock Plans Stock Plans (Schedule of RSU Expense by Vesting Type) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,097	$ 1,055	$ 3,759	$ 2,906
Restricted stock unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	824	374	2,305	1,049
Restricted stock unit awards | Service-based
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	544	400	1,613	975
Performance restricted stock unit awards | Performance objectives
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	30	(60)	71	(28)
Performance restricted stock unit awards | Market-condition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 250	$ 34	$ 621	$ 102