Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Intangible Assets [Abstract]

Intangible Assets Other Than Goodwill

	2017						2016
(in thousands)	Gross		Accumulated Amortization		Net		Gross		Accumulated Amortization		Net		Useful Life (in years)	Weighted Average Useful Life Remaining (in years)
Intangible assets with finite lives:
Customer relationships	$	105,505	$	(57,796)	$	47,709	$	99,067	$	(46,252)	$	52,815	1-14	6
Acquired technology		54,716		(39,644)		15,072		52,881		(27,543)		25,338	1-16	2
Trade names		25,813		(15,552)		10,261		28,110		(16,015)		12,095	1-8	6
Patent costs		17,909		(7,338)		10,571		16,263		(5,873)		10,390	1-20	15
Trade secrets		19,431		(11,530)		7,901		19,134		(9,383)		9,751	7	4
Acquired patents		16,661		(11,969)		4,692		16,965		(10,674)		6,291	1-6	8
Other		20,012		(17,435)		2,577		23,431		(18,610)		4,821	2-4	2
Total intangible assets	$	260,047	$	(161,264)	$	98,783	$	255,851	$	(134,350)	$	121,501	1-20	6