Intangible Assets (Intangible Assets Other Than Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 258,227	$ 260,047
Intangible assets with finite lives: Accumulated Amortization	(166,427)	(161,264)
Intangible assets with finite lives: Net	$ 91,800	98,783
Weighted average useful life remaining (in years)	6 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 107,094	105,505
Intangible assets with finite lives: Accumulated Amortization	(61,287)	(57,796)
Intangible assets with finite lives: Net	$ 45,807	47,709
Weighted average useful life remaining (in years)	6 years
Acquired technology
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 50,370	54,716
Intangible assets with finite lives: Accumulated Amortization	(38,108)	(39,644)
Intangible assets with finite lives: Net	$ 12,262	15,072
Weighted average useful life remaining (in years)	2 years
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 25,972	25,813
Intangible assets with finite lives: Accumulated Amortization	(16,381)	(15,552)
Intangible assets with finite lives: Net	$ 9,591	10,261
Weighted average useful life remaining (in years)	6 years
Patent costs
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 18,230	17,909
Intangible assets with finite lives: Accumulated Amortization	(8,069)	(7,338)
Intangible assets with finite lives: Net	$ 10,161	10,571
Weighted average useful life remaining (in years)	15 years
Trade secrets
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 19,601	19,431
Intangible assets with finite lives: Accumulated Amortization	(12,117)	(11,530)
Intangible assets with finite lives: Net	$ 7,484	7,901
Weighted average useful life remaining (in years)	4 years
Acquired patents
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 16,690	16,661
Intangible assets with finite lives: Accumulated Amortization	(12,390)	(11,969)
Intangible assets with finite lives: Net	$ 4,300	4,692
Weighted average useful life remaining (in years)	8 years
Other
Finite-Lived Intangible Assets [Line Items]
Intangible assets with finite lives: Gross	$ 20,270	20,012
Intangible assets with finite lives: Accumulated Amortization	(18,075)	(17,435)
Intangible assets with finite lives: Net	$ 2,195	$ 2,577
Weighted average useful life remaining (in years)	2 years