XML 44 R28.htm IDEA: XBRL DOCUMENT v3.8.0.1
Patents (Tables)
 12 Months Ended
Dec. 31, 2017
Patents [Abstract]  
Patents
The gross carrying amounts and accumulated amortization related to investments in intangible assets as of December 31, 2017 and 2016 are as follows (in thousands): 
 
 
2017
 
2016
 
 
 
 
 
Gross carrying amount - patents                                                        
 
$
444,137

 
$
444,362

Accumulated amortization - patents(1)                                                                         
 
(382,220
)
 
(358,043
)
Patents, net                                                                             
 
$
61,917

 
$
86,319