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Patents (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]          
Asset Impairment Charges     $ 28,210,000    
Patents, accumulated amortization $ 425,990,000   $ 425,990,000   $ 382,220,000
Weighted average useful life of patents and patent rights     2 years    
Impairment of Intangible Assets (Excluding Goodwill) $ 0 $ 2,248,000 $ 29,210,000 $ 2,248,000  
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     5 years