Income (loss) per common share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Numerator:
Net income (loss)	$ 1,071	$ (3,305)	$ (4,578)	$ (11,242)	$ (36,670)
Denominator:
Basic-weighted average shares (in shares)	17,872,000	17,534,000	17,799,000	17,490,000
Effect of dilutive stock options (in shares)	0	0	0	0
Diluted-weighted average shares (in shares)	17,872,000	17,534,000	17,799,000	17,490,000
Basic loss per common share (in dollars per share)	$ 0.06	$ (0.19)	$ (0.26)	$ (0.64)
Diluted loss per common share (in dollars per share)	$ 0.06	$ (0.19)	$ (0.26)	$ (0.64)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total options outstanding (in shares)	400,000	443,000	381,000	479,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred stock units granted			527,000	390,000