Loss per common share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
Net loss	$ (5,663)	$ (13,668)	$ (10,241)	$ (24,910)
Denominator:
Basic-weighted average shares (in shares)	17,917,000	17,663,000	17,839,000	17,557,000
Effect of dilutive stock options (in shares)	0	0	0	0
Diluted-weighted average shares (in shares)	17,917,000	17,663,000	17,839,000	17,557,000
Basic loss per common share (in dollars per share)	$ (0.32)	$ (0.77)	$ (0.57)	$ (1.42)
Diluted loss per common share (in dollars per share)	$ (0.32)	$ (0.77)	$ (0.57)	$ (1.42)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total options outstanding (in shares)	397,000	687,000	371,000	684,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred stock units granted			486,000	366,000