Patents (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Patents, accumulated amortization	$ 126,795,000		$ 112,323,000
Weighted average useful life of patents and patent rights	7 years
Investments in patents/ patent rights	987,000	4,010,000
Patent acquisition costs included in accrued expenses	15,250,000	0
Accelerated amortization expense - up-front payments	48,000	483,000
Accelerated amortization expense (impairment)	$ 2,565,000
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