Earnings (loss) per share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Basic earnings per share [Abstract]
Weighted average common shares outstanding (in shares)	201,528,000	200,744,000
Net loss	$ (19,555)	$ (33,661)
Basic loss per share (in dollars per share)	$ (0.10)	$ (0.17)
Diluted earnings per share [Abstract]
Weighted-average shares - Basic (in shares)	201,528,000	200,744,000
Common stock equivalents (in shares)	0	0
Weighted-average shares - Diluted (in shares)	201,528,000	200,744,000
Net loss	$ (19,555)	$ (33,661)
Diluted loss per share (in dollars per share)	$ (0.10)	$ (0.17)
Participating Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive participating securities excluded from EPS calculation (in shares)	1,100,000	1,300,000
Common Stock Equivalents [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive participating securities excluded from EPS calculation (in shares)	56,000,000	55,600,000