3. Patents and Licenses

12 Months Ended

Dec. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Patents and Licenses

Purchased patents and licenses paid for the use of other entities’ patents are amortized over the useful life of the patent or license.  The following tables provide information regarding patents and licenses (dollars in thousands):

December 31, 2015						December 31, 2014
Weighted Average Original Life (years)		Gross Carrying Amount		Accumulated Amortization		Weighted Average Original Life (years)		Gross Carrying Amount		Accumulated Amortization
	15.67	$	13,840	$	11,647		15.67	$	13,840	$	11,302

Aggregate amortization expense for patents and licenses was $345,000, $269,000 and $179,000 for 2015, 2014 and 2013, respectively.  Estimated future amortization expense for each of the years set forth below ending December 31 is as follows (in thousands):

2016	$	251
2017	$	155
2018	$	123
2019	$	123
2020	$	119