Purchased intangible assets

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Purchased intangible assets

Purchased intangible assets

Purchased intangible assets consist of the following (in thousands): 

	December 31, 2018							December 31, 2017
	Gross Assets		Accumulated Amortization			Net Assets		Gross Assets		Accumulated Amortization			Net Assets
Technology and patents	$	37,029	$	(34,995	)	$	2,034	$	37,684	$	(34,923	)	$	2,761
Customer relationships	15,146		(15,026		)	120		15,425		(14,835		)	590
Leasehold interest	1,238		(374		)	864		1,309		(366		)	943
	$	53,413	$	(50,395	)	$	3,018	$	54,418	$	(50,124	)	$	4,294

Amortization expense relating to technology and patents and the leasehold interest intangible assets is included within cost of goods sold, and customer relationships and the non-compete agreements within operating expenses. The following table presents details of the amortization expense of the Company’s purchased intangible assets as reported in the consolidated statements of operations (in thousands): 

	Years ended December 31,
	2018		2017		2016
Cost of goods sold	$	756	$	869	$	2,871
Operating expenses	475		472		1,609
Total	$	1,231	$	1,341	$	4,480

The estimated future amortization expense of purchased intangible assets as of December 31, 2018, is as follows (in thousands): 

2019	$	856
2020	737
2021	644
2022	28
2023	28
Thereafter	725
	$	3,018