Summary of Significant Accounting Policies Basic Earnings Per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share, Basic, by Common Class [Line Items]
Net income (loss)	$ 3,895	$ 30,301	$ (3,795)	$ 49,674
Net income (loss) available to common stockholders	3,816	29,662	(3,795)	48,641
Earnings Per Share, Basic [Member]
Earnings Per Share, Basic, by Common Class [Line Items]
Income (expense) attributable to participating securities	$ (79)	$ (639)	$ 0	$ (1,033)