Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 52,702	$ 52,724
Accumulated Amortization	(39,625)	(38,892)
Net Carrying Amount	13,077	13,832
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	30,414	30,447
Accumulated Amortization	(24,006)	(23,615)
Net Carrying Amount	$ 6,408	$ 6,832
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	$ 16,964	$ 17,219
Accumulated Amortization	(12,073)	(11,786)
Net Carrying Amount	$ 4,891	$ 5,433
Weighted Average Amortization Period	8 years 5 months	8 years 4 months 18 days
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,284	$ 1,286
Accumulated Amortization	(1,284)	(1,286)
Net Carrying Amount	$ 0	$ 0
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	$ 1,435	$ 1,436
Accumulated Amortization	(1,435)	(1,436)
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	$ 2,343	$ 2,074
Accumulated Amortization	(592)	(534)
Net Carrying Amount	$ 1,751	$ 1,540
Weighted Average Amortization Period	12 years 7 months	12 years 4 months 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