Intangible Assets

12 Months Ended

Dec. 31, 2014

Note 6 Intangible Assets

Intangible assets other than goodwill at December 31, 2014 and December 31, 2013 are as follows:


	2014						2013
(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:
Licenses	$	5,875	$	(5,875)	$	—	$	5,875	$	(5,875)	$	—	N/A	N/A
Patent costs		20,733		(7,369)		13,364		21,545		(5,960)		15,585	5 - 20	3
Acquired technology		57,383		(18,241)		39,142		30,095		(13,615)		16,480	3 - 10	4
Internally developed software		9,073		(5,517)		3,556		18,097		(12,863)		5,234	1 - 8	<1
Customer relationships		157,139		(36,975)		120,164		95,793		(18,283)		77,510	3 - 11	2
Non-compete agreements		35,469		(11,784)		23,685		16,848		(6,666)		10,182	3 - 11	3
Trade names		21,800		(4,455)		17,345		9,302		(2,211)		7,091	2 - 10	5
Other		39,100		(6,905)		32,195		11,598		(4,081)		7,517	4 - 10	1
Intangible assets with indefinite lives:
Trademarks		2,110		—		2,110		2,110		—		2,110	N/A	N/A
Total intangible assets	$	348,682	$	(97,121)	$	251,561	$	211,263	$	(69,554)	$	141,709	1 - 20	4

Amortization expense related to costs incurred to internally develop and extend patents in the United States and various other countries was $281, $250 and $215 for the years ended December 31, 2014, 2013 and 2012, respectively.

Amortization expense related to acquired intangible assets was $39,203, $20,447 and $12,573 for the years ended December 31, 2014, 2013 and 2012, respectively. Amortization of these intangible assets is calculated on a straight-line basis over periods ranging from one year to twenty years.

Annual amortization expense for intangible assets is expected to be $50,888 in 2015, $46,105 in 2016, $41,802 in 2017, $33,280 in 2018 and $24,706 in 2019.