Intangible Asset and Goodwill (Details 3) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Components of intangible assets
Accumulated Amortization	$ (273,177)		$ (268,534)
Finite-Lived Intangible Assets	53,907
Indefinite-lived Intangible Assets (Excluding Goodwill)	1,600
Intangible Assets, Gross (Excluding Goodwill)	328,684		328,470
Amortization expense for intangible assets	4,988	$ 10,531
Intangible Assets, Net	55,507		59,936
Existing technology
Components of intangible assets
Gross Carrying Amount	259,389		258,903
Accumulated Amortization	(217,734)		(213,824)
Finite-Lived Intangible Assets	$ 41,655		$ 45,079
Existing technology \| Minimum [Member]
Components of intangible assets
Useful Life (in years)	3 years		3 years
Existing technology \| Maximum [Member]
Components of intangible assets
Useful Life (in years)	10 years		10 years
Customer Contracts [Member]
Components of intangible assets
Gross Carrying Amount	$ 67,395		$ 67,667
Accumulated Amortization	(55,143)		(54,410)
Finite-Lived Intangible Assets	$ 12,252		$ 13,257
Customer Contracts [Member] \| Minimum [Member]
Components of intangible assets
Useful Life (in years)	1 year		1 year
Customer Contracts [Member] \| Maximum [Member]
Components of intangible assets
Useful Life (in years)	10 years		10 years
Non-compete agreements
Components of intangible assets
Useful Life (in years)	3 years		3 years
Gross Carrying Amount	$ 300		$ 300
Accumulated Amortization	(300)		(300)
Finite-Lived Intangible Assets	0		0
Favorable contracts
Components of intangible assets
Finite-Lived Intangible Assets	500		900
Cash received related to favorable contracts	500	$ 900
In Process Research and Development [Member]
Components of intangible assets
Indefinite-lived Intangible Assets (Excluding Goodwill)	$ 1,600		$ 1,600

Represents the cash received on account of intangible assets.

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

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Amount before accumulated amortization of intangible assets, excluding goodwill.

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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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