Property and equipment (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property And Equipment Narrative Details
Depreciation expense	$ 429,000	$ 414,000	$ 923,000
Property and equipment under capital lease	704,000	704,000
Accumulated depreciation related to assets under capital lease	$ 704,000	$ 704,000