Intangible Assets

12 Months Ended

Dec. 31, 2016

Goodwill And Intangible Assets Disclosure [Abstract]

4. Intangible Assets

Intangible assets consist of the following (in thousands):

	As of
	December 31, 2016			December 31, 2015
Patents issued	$	4,892		$	6,180
Patents pending		385			1,156
Trademarks		40			40
Total intangible assets		5,317			7,376
Less patent amortization		(1,316	)		(1,407	)
Intangible assets, net	$	4,001		$	5,969

Amortization commences upon patent issuance. The useful life of the patents, once issued, will not exceed 20 years, and will depend on the nature of the patent. The average estimated amortization period of the Company's current portfolio is approximately 17 years from the date of patent issuance factoring in approximately 3 years on average for prosecution of the pending patents.

During fiscal 2016, the Company identified certain patents with carrying values deemed to not be recoverable. Based on this evaluation, the Company recorded an impairment charge of $1.0 million related to these patents. Fair value was based on expected future cash flows using Level 3 inputs under ASC 820. The cash flows are those expected to be generated by the market participants, discounted at the risk-free rate of interest. Because of changing market conditions (i.e., less marketplace demand and rising interest rates), it is reasonably possible that the estimate of expected future cash flows may change in the near term resulting in the need to further adjust our determination of fair value. As discussed in Note 1, Impairment of Long-Lived Assets, the Company did not record any impairment-related expenses during the year ended December 31, 2015.

The following table presents patent amortization expense included in the Consolidated Statement of Operations (in thousands):

	Years Ended December 31,
	2016		2015		2014
Amortization expense	$	489	$	995	$	688

Estimated future aggregate annual amortization expense for both issued and pending intangible assets is as follows (in thousands):

As of December 31:
2017	$	416
2018		324
2019		298
2020		288
2021		276
Thereafter		2,359
Total	$	3,961