Loss per common share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Net loss	$ (2,603)	$ 1,071	$ (5,858)	$ (4,578)
Denominator:
Basic-weighted average shares (in shares)	18,028,000	17,872,000	17,976,000	17,799,000
Effect of dilutive stock options (in shares)	0	0	0	0
Diluted-weighted average shares (in shares)	18,028,000	17,872,000	17,976,000	17,799,000
Basic (loss) income per common share (in dollars per share)	$ (0.14)	$ 0.06	$ (0.33)	$ (0.26)
Diluted (loss) income per common share (in dollars per share)	$ (0.14)	$ 0.06	$ (0.33)	$ (0.26)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total options outstanding (in shares)	305,000	400,000	315,000	381,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred stock units granted	498,000	527,000