Purchased Intangible Assets and Goodwill (Changes in Purchased Intangibles Balances) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets [Roll Forward]
Beginning balance	$ 15,225	$ 16,364
Amortization	(1,073)	(1,039)	$ (1,000)
Foreign currency impact	413	(100)
Ending balance	$ 14,565	$ 15,225	$ 16,364