Intangible assets (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended
	Oct. 31, 2010	Dec. 31, 2012	Dec. 31, 2011
Intangible Assets Narrative Details
Gross value of intangible assets		$ 2,300,000	$ 2,300,000
Amortization expense		184,000	185,000
Impairment of intangible assets		284,000	0
Number of patents abandoned in prosecution		35
Number of patents and patents pending purchased	195
Issuance of common stock for payment of intellectual property, shares	104,000
Cash payments made under patent purchase agreement		$ 330,000	$ 220,000