Summary of Significant Accounting Policies (Reconciliation of Net Income to Taxable Income Before Dividends Paid Deduction) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounting Policies [Abstract]
Net income (loss)	$ 96,309	$ 65,262	$ (271,490)
Book/tax differences	(11,127)	74,065	441,784
Taxable income before adjustments	85,182	139,327	170,294
Less: capital gains	0	(62,403)	(10,828)
Adjusted taxable income subject to 90% distribution requirement	$ 85,182	$ 76,924	$ 159,466