Intangible Assets

6 Months Ended

Jun. 30, 2016

(4) Intangible Assets

Intangible assets, net, other than goodwill, as of June 30, 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	$	16,377	$	(5,457)	$	10,920	$	16,251	$	(4,895)	$	11,356	1-19	8
Acquired technology		53,161		(22,075)		31,086		52,809		(16,405)		36,404	2-15	4
Internally developed software		4,730		(3,220)		1,510		4,730		(2,919)		1,811	3	3
Customer relationships		102,585		(42,315)		60,270		101,933		(36,158)		65,775	2-15	7
Non-compete agreements		11,808		(8,916)		2,892		12,163		(8,558)		3,605	2-5	3
Trade names		28,352		(14,386)		13,966		28,108		(12,498)		15,610	1-9	6
Other		46,202		(25,765)		20,437		46,435		(23,530)		22,905	1-7	5
Total intangible assets	$	263,215	$	(122,134)	$	141,081	$	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 $81 and $165 for the quarter and six months ended June 30, 2016, respectively, compared to $76 and $151 for the quarter and six months ended June 30, 2015, respectively.

Amortization expense related to all other intangible assets was $8,779 and $17,514 for the quarter and six months ended June 30, 2016, respectively, compared to $17,405 and $31,846 for the quarter and six months ended June 30, 2015, respectively.

Annual amortization expense for intangible assets is expected to be $35,358, $32,134, $26,962, $21,626 and $16,932 for the years ending 2016, 2017, 2018, 2019, and 2020, respectively.