Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Mortgage-backed securities, at fair value (including pledged assets of $23,683,027 and $22,591,973 at March 31, 2013 and December 31, 2012, respectively)	$ 25,162,730	$ 23,919,251
Cash and cash equivalents	315,253	168,424
Restricted cash	239,417	281,021
Unsettled purchased mortgage-backed securities, at fair value	113,171	138,338
Receivable for securities sold		1,587,535
Accrued interest receivable	74,691	77,113
Principal payments receivable	151,200	190,832
Debt security, held to maturity, at cost	15,000	15,000
Other assets	27,399	26,604
Total assets	26,098,861	26,404,118
Liabilities and shareholders' equity
Repurchase agreements	22,586,932	22,866,429
Payable for unsettled securities	138,688	137,121
Accrued interest payable	5,040	7,592
Interest rate hedge liability	220,040	243,945
Dividend payable	73,809	73,804
Accounts payable and other liabilities	2,087	2,363
Total liabilities	23,026,596	23,331,254
Shareholders' equity:
7.625% Series A Cumulative Redeemable Preferred stock, $.001 par value, 25,000,000 shares authorized, 11,500,000 shares issued and outstanding at March 31, 2013 and December 31, 2012, respectively ($287,500 aggregate liquidation preference)	278,252	278,252
Common stock, $.001 par value, 200,000,000 shares authorized, 98,830,054 and 98,822,654 shares issued and outstanding at March 31, 2013 and December 31, 2012, respectively	99	99
Additional paid-in capital	2,494,932	2,494,303
Retained earnings (accumulated deficit)	29,934	37,356
Accumulated other comprehensive income	269,048	262,854
Total shareholders' equity	3,072,265	3,072,864
Total liabilities and shareholders' equity	$ 26,098,861	$ 26,404,118