Earnings (loss) per share (Details) (USD $) In Thousands, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Basic earnings per share [Abstract]
Average common shares outstanding (in shares)	201,109,000	200,077,000	200,983,000	168,429,000
Net (loss) income	$ (165,205)	$ (51,528)	$ (350,598)	$ (177,068)
Basic (loss) earnings per share (in dollars per share)	$ (0.82)	$ (0.26)	$ (1.74)	$ (1.05)
Diluted earnings per share [Abstract]
Weighted-average shares - Basic (in shares)	201,109,000	200,077,000	200,983,000	168,429,000
Common stock equivalents (in shares)	0	0	0	0
Weighted-average shares - Diluted (in shares)	201,109,000	200,077,000	200,983,000	168,429,000
Net (loss) income	$ (165,205)	$ (51,528)	$ (350,598)	$ (177,068)
Diluted (loss) earnings per share (in dollars per share)	$ (0.82)	$ (0.26)	$ (1.74)	$ (1.05)
Participating Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive participating securities excluded from EPS calculation (in shares)	1,000,000	1,800,000	1,100,000	1,800,000
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)	55,500,000	62,300,000	55,600,000	51,300,000