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Patents (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]          
Patents, accumulated amortization $ 421,038,000   $ 421,038,000   $ 382,220,000
Weighted average useful life of patents and patent rights     2 years    
Impairment of Intangible Assets (Excluding Goodwill) $ 29,210,000 $ 0 $ 29,210,000 $ 0  
Minimum [Member]          
Finite-Lived Intangible Assets [Line Items]          
Useful life of patents and patent rights     1 year    
Maximum [Member]          
Finite-Lived Intangible Assets [Line Items]          
Useful life of patents and patent rights     6 years