INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Definite-lived intangible assets
Gross value of definite-lived intangible assets	$ 82,042	$ 82,532
Accumulated amortization	(54,231)	(53,044)
Net definite-lived intangible assets	27,811	29,488
Indefinite-lived intangible assets
Total intangible assets, net	29,116	30,793
Trademarks and trade names
Indefinite-lived intangible assets
Total intangible assets, net	1,305	1,305
Customer relationships
Definite-lived intangible assets
Gross value of definite-lived intangible assets	24,638	24,764
Accumulated amortization	(17,608)	(17,219)
Unpatented technology
Definite-lived intangible assets
Gross value of definite-lived intangible assets	14,887	15,098
Accumulated amortization	(4,139)	(3,760)
Patented technology
Definite-lived intangible assets
Gross value of definite-lived intangible assets	2,601	2,616
Accumulated amortization	(2,380)	(2,348)
Tradename
Definite-lived intangible assets
Gross value of definite-lived intangible assets	12,407	12,566
Accumulated amortization	(3,820)	(3,672)
Backlog
Definite-lived intangible assets
Gross value of definite-lived intangible assets	17,760	17,760
Accumulated amortization	(17,760)	(17,760)
All other
Definite-lived intangible assets
Gross value of definite-lived intangible assets	9,749	9,728
Accumulated amortization	$ (8,524)	$ (8,285)

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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-Publisher FASB
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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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