Patents (Details) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Patents, accumulated amortization	$ 139,327,000		$ 112,323,000
Weighted average useful life of patents and patent rights	6 years
Investments in patents/ patent rights	22,096,000	6,260,000
Patent acquisition costs included in accrued expenses	3,000,000	8,508,000
Accelerated amortization expense - up-front payments	312,000	612,000
Accelerated amortization expense (termination)	2,702,000	956,000
Proceeds from patent sale	$ 3,500,000
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	4 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Useful life of patents and patent rights	10 years
Finite lived intangible asset acquired during the year, useful life	10 years