Fair Value of Financial Instruments (Details 2) (USD $)	Sep. 30, 2011		Dec. 31, 2010
Financial Assets:
Agency MBS	$ 7,519,002,000		$ 5,980,623,000
Non-Agency MBS, including MBS transferred to consolidated VIEs	3,889,310,000		2,078,087,000
Restricted cash	22,498,000		41,927,000
Linked Transactions	64,494,000		179,915,000
Derivative hedging instruments	81,000
Financial Liabilities:
Repurchase agreements	8,017,663,000		5,992,269,000
Securitized debt	958,406,000	[1]	220,933,000	[1]
Derivative hedging instruments	134,712,000		139,142,000
Carrying value
Financial Assets:
Agency MBS	7,519,002,000		5,980,623,000
Non-Agency MBS, including MBS transferred to consolidated VIEs	3,889,310,000		2,078,087,000
Cash and cash equivalents	421,026,000		345,243,000
Restricted cash	22,498,000		41,927,000
Linked Transactions	64,494,000		179,915,000
Derivative hedging instruments	81,000
Financial Liabilities:
Repurchase agreements	8,017,663,000		5,992,269,000
Securitized debt	958,406,000		220,933,000
Derivative hedging instruments	134,712,000		139,142,000
Estimated fair value
Financial Assets:
Agency MBS	7,519,002,000		5,980,623,000
Non-Agency MBS, including MBS transferred to consolidated VIEs	3,889,310,000		2,078,087,000
Cash and cash equivalents	421,026,000		345,243,000
Restricted cash	22,498,000		41,927,000
Linked Transactions	64,494,000		179,915,000
Derivative hedging instruments	81,000
Financial Liabilities:
Repurchase agreements	8,018,144,000		5,993,769,000
Securitized debt	952,414,000		221,209,000
Derivative hedging instruments	$ 134,712,000		$ 139,142,000

[1] Securitized Debt included in the Consolidated Balance Sheet at September 30, 2011 and December 31, 2010, represents third-party liabilities of consolidated VIEs and excludes liabilities of the VIEs acquired by the Company that eliminate on consolidation. The third-party beneficial interest holders in the VIEs have no recourse to the general credit of the Company. (See Notes 9 and 14 for further discussion.)