Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 49,831	$ 48,470
Accumulated Amortization	(37,510)	(36,104)
Net Carrying Amount	12,321	12,366
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	29,040	27,882
Accumulated Amortization	(22,879)	(22,197)
Net Carrying Amount	$ 6,161	$ 5,685
Weighted Average Amortization Period	5 years 3 months 18 days	5 years 3 months 18 days
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 15,973	$ 15,978
Accumulated Amortization	(11,110)	(10,457)
Net Carrying Amount	$ 4,863	$ 5,521
Weighted Average Amortization Period	8 years	8 years 18 days
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,287	$ 1,289
Accumulated Amortization	(1,287)	(1,283)
Net Carrying Amount	$ 0	$ 6
Weighted Average Amortization Period	2 years 1 month	2 years 1 month 12 days
Non-compete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,437	$ 1,439
Accumulated Amortization	(1,437)	(1,439)
Net Carrying Amount	$ 0	$ 0
Weighted Average Amortization Period	2 years 3 months 12 days	2 years 3 months 12 days
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,832	$ 1,620
Accumulated Amortization	(562)	(493)
Net Carrying Amount	$ 1,270	$ 1,127
Weighted Average Amortization Period	13 years 3 months	13 years 1 month 18 days
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 262	$ 262
Accumulated Amortization	(235)	(235)
Net Carrying Amount	$ 27	$ 27
Weighted Average Amortization Period	2 years 8 months 12 days	2 years 8 months 18 days