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Patents (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]          
Patents, accumulated amortization $ 349,646,000   $ 349,646,000   $ 281,495,000
Weighted average useful life of patents and patent rights     5 years    
Investments in patents/ patent rights     $ 1,000,000 $ 19,504,000  
Impairment of patent-related intangible assets $ 0 $ 0 $ 40,165,000 $ 0  
Minimum [Member]          
Finite-Lived Intangible Assets [Line Items]          
Useful life of patents and patent rights     1 year    
Finite lived intangible asset acquired during the year, useful life     2 years    
Maximum [Member]          
Finite-Lived Intangible Assets [Line Items]          
Useful life of patents and patent rights     8 years    
Finite lived intangible asset acquired during the year, useful life     9 years