Intangible assets and Goodwill

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets and Goodwill

Intangible assets and Goodwill

The following table summarizes intangible assets as of December 31, 2018 and 2017 (in thousands):

	Weighted-Average	December 31, 2018
	Amortization Period (Years)	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Trademarks	5	$	1,900	$	(1,900	)	$	—
Technology	3	1,678		(1,192		)	486
Customer relationships	5	1,300		(1,300		)	—
Total		$	4,878	$	(4,392	)	$	486

	Weighted-Average	December 31, 2017
	Amortization Period (Years)	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Trademarks	5	$	1,900	$	(1,678	)	$	222
Technology	3	1,453		(646		)	807
Customer relationships	5	1,300		(1,148		)	152
Total		$	4,653	$	(3,472	)	$	1,181

Amortization expense related to intangible assets was $0.9 million, $1.1 million, and $0.9 million for the years ended December 31, 2018, 2017, and 2016, respectively. The estimated future amortization expense of purchased intangible assets as of December 31, 2018, is as follows (in thousands):

	Total
2019	$	398
2020	75
2021	13
Thereafter	—
Total	$	486

Goodwill was $2.1 million and $1.9 million for the years ended December 31, 2018 and December 31, 2017, respectively.

In January 2019, the Company sold certain intellectual property. As of December 31, 2018, the net carrying amount of the goodwill was $1.7 million. The proceeds from the sale exceeded the carrying value of the intellectual property.