Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets
Mortgage-backed securities, at fair value (including pledged assets of $19,272,664 and $22,591,973 at September 30, 2013 and December 31, 2012, respectively)	$ 19,843,830	$ 23,919,251
Cash and cash equivalents	547,536	168,424
Restricted cash	241,853	281,021
Unsettled purchased mortgage-backed securities, at fair value	628,684	138,338
Receivable for securities sold	548,942	1,587,535
Accrued interest receivable	62,921	77,113
Principal payments receivable	156,758	190,832
Debt security, held to maturity, at cost	15,000	15,000
Interest rate hedge asset	13,626
Other assets	28,151	26,604
Total assets	22,087,301	26,404,118
Liabilities and shareholders' equity
Repurchase agreements	18,829,771	22,866,429
Payable for unsettled securities	625,758	137,121
Accrued interest payable	3,901	7,592
Interest rate hedge liability	147,954	243,945
Futures contract liability	44,593
Dividend payable	58,478	73,804
Accounts payable and other liabilities	3,205	2,363
Total liabilities	19,713,660	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 September 30, 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, 97,908,523 and 98,822,654 shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively	98	99
Additional paid-in capital	2,475,134	2,494,303
Retained earnings (accumulated deficit)	(295,464)	37,356
Accumulated other comprehensive (loss) income	(84,379)	262,854
Total shareholders' equity	2,373,641	3,072,864
Total liabilities and shareholders' equity	$ 22,087,301	$ 26,404,118