XML 94 R33.htm IDEA: XBRL DOCUMENT v3.20.1
5. Patents (Tables)
12 Months Ended
Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]  
Schedule of intangible assets

   2019   2018 
Gross carrying amount - patents  $330,588   $326,167 
Accumulated amortization - patents(1)   (322,774)   (319,580)
Patents, net  $7,814   $6,587 

 

(1) Includes patent impairment charges for the applicable periods.