Intangible Assets

3 Months Ended

Mar. 31, 2016

(5) Intangible Assets

Intangible assets, net, other than goodwill as of March 31, 2016 and December 31, 2015 were as follows:



	2016						2015
(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:
Patent costs	$	16,547	$	(5,248)	$	11,299	$	16,251	$	(4,895)	$	11,356	1-19	8
Acquired technology		53,735		(19,497)		34,238		52,809		(16,405)		36,404	2-15	4
Internally developed software		4,730		(3,069)		1,661		4,730		(2,919)		1,811	3	3
Customer relationships		103,825		(39,768)		64,057		101,933		(36,158)		65,775	2-15	7
Non-compete agreements		12,043		(8,722)		3,321		12,163		(8,558)		3,605	2-5	3
Trade names		28,347		(13,456)		14,891		28,108		(12,498)		15,610	1-9	6
Other		46,455		(24,556)		21,899		46,435		(23,530)		22,905	1-7	5
Total intangible assets	$	265,682	$	(114,316)	$	151,366	$	262,429	$	(104,963)	$	157,466	1-19	5

Amortization expense related to costs incurred to internally develop and extend patents in the United States and various other countries was $84 and $75 for the quarters ended March 31, 2016 and 2015, respectively.

Amortization expense related to all other intangible assets was $8,735 and $14,441 for the quarters ended March 31, 2016 and 2015, respectively.

Annual amortization expense for intangible assets is expected to be $35,180, $32,233, $27,022, $21,737 and $17,200 for the years ending 2016, 2017, 2018, 2019, and 2020, respectively.