Intangible assets (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Intangible Assets Narrative Details
Gross value of intangible assets	$ 1,700,000	$ 2,300,000
Amortization expense	158,000	184,000
Impairment of intangible assets	$ 277,000	$ 284,000
Number of patents abandoned in prosecution	42	35