Intangible Asset and Goodwill (Details 3) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Components of intangible assets
Accumulated Amortization	$ (252,491)		$ (240,480)
Finite-Lived Intangible Assets	76,983
Indefinite-Lived Intangible Assets (Excluding Goodwill)	5,100
Intangible Assets, Gross (Excluding Goodwill)	334,574		332,202
Amortization expense for intangible assets	10,531	$ 10,488
Intangible Assets, Net	82,083		91,722
Existing technology
Components of intangible assets
Gross Carrying Amount	259,017		258,008
Accumulated Amortization	(200,671)		(191,554)
Finite-Lived Intangible Assets	$ 58,346		$ 66,454
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	$ 70,157		$ 68,794
Accumulated Amortization	(51,520)		(48,626)
Finite-Lived Intangible Assets	$ 18,637		$ 20,168
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	1,300		1,700
Cash received related to favorable contracts	900	$ 1,200
In Process Research and Development [Member]
Components of intangible assets
Indefinite-Lived Intangible Assets (Excluding Goodwill)	$ 5,100		$ 5,100

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

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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

No definition available.

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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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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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount before accumulated amortization of intangible assets, excluding goodwill.

+ References

No definition available.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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