Accumulated Other Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands	Jun. 30, 2011		Dec. 31, 2010
Accumulated Other Comprehensive Income
Unrealized gain on securities, net	$ 259,168		$ 162,312
Unrealized loss on unsettled securities	37		(64)
Unrealized loss on short term investment	(143)	[1]	(136)	[1]
Unrealized loss on derivative instruments	(111,789)		(56,221)
Accumulated other comprehensive income	$ 147,273		$ 105,891

[1] This line item is included in Other Assets on the Balance Sheet.