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Patents (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]          
Patents, accumulated amortization $ 376,777,000   $ 376,777,000   $ 358,043,000
Weighted average useful life of patents and patent rights     4 years    
Impairment of patent-related intangible assets $ 2,248,000 $ 0 $ 2,248,000 $ 40,165,000  
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     7 years