Earnings per share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Numerator:
Net loss	$ (8,062)	$ (6,829)
Denominator:
Weighted-average number of shares-basic (in shares)	35,968,064	36,045,839
Dilutive securities-equity awards (in shares)	0	0
Weighted-average number of shares-diluted (in shares)	35,968,064	36,045,839
Loss per share-basic (in dollars per share)	$ (0.22)	$ (0.19)
Loss per share-diluted (in dollars per share)	$ (0.22)	$ (0.19)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation (in shares)	5,000,000	4,500,000