Intangible Assets (Intangible Assets Other Than Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 254,288	$ 252,628
Intangible assets with finite lives: Accumulated Amortization	(186,013)	(201,375)
Intangible assets with finite lives: Net	$ 68,275	51,253
Weighted average useful life remaining (in years)	5 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 103,332	102,023
Intangible assets with finite lives: Accumulated Amortization	(67,129)	(74,349)
Intangible assets with finite lives: Net	$ 36,203	27,674
Weighted average useful life remaining (in years)	5 years
Acquired technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 52,691	54,067
Intangible assets with finite lives: Accumulated Amortization	(47,546)	(51,241)
Intangible assets with finite lives: Net	$ 5,145	2,826
Weighted average useful life remaining (in years)	2 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 25,096	23,668
Intangible assets with finite lives: Accumulated Amortization	(17,669)	(18,402)
Intangible assets with finite lives: Net	$ 7,427	5,266
Weighted average useful life remaining (in years)	5 years
Patent costs
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 11,032	11,678
Intangible assets with finite lives: Accumulated Amortization	(8,382)	(9,079)
Intangible assets with finite lives: Net	$ 2,650	2,599
Weighted average useful life remaining (in years)	14 years
Trade secrets
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 19,374	19,296
Intangible assets with finite lives: Accumulated Amortization	(13,574)	(15,076)
Intangible assets with finite lives: Net	$ 5,800	4,220
Weighted average useful life remaining (in years)	3 years
Acquired patents
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 16,212	16,184
Intangible assets with finite lives: Accumulated Amortization	(13,160)	(14,340)
Intangible assets with finite lives: Net	$ 3,052	1,844
Weighted average useful life remaining (in years)	7 years
Other
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 26,551	25,712
Intangible assets with finite lives: Accumulated Amortization	(18,553)	(18,888)
Intangible assets with finite lives: Net	$ 7,998	$ 6,824
Weighted average useful life remaining (in years)	1 year

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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