Summary of Significant Accounting Policies Diluted Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share, Diluted, by Common Class [Line Items]
Net (loss) income	$ (7,690)	$ 19,373
Net (loss) income available to common stockholders	(7,690)	18,976
Earnings Per Share, Diluted [Member]
Earnings Per Share, Diluted, by Common Class [Line Items]
Income attributable to participating securities	$ 0	$ (397)