Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities
Net income (loss)	$ (124,168)	$ 242,498
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net amortization of premium related to mortgage-backed securities	139,205	112,736
Amortization related to interest rate swap agreements	239	275
Share based compensation expense	1,893	1,301
Hedge ineffectiveness	(205)	321
Net (gain) loss on sale of mortgage-backed securities	214,333	(25,244)
Impairment loss on mortgage-backed securities	8,102
Net unrealized loss on sale of futures contracts	44,593
Changes in operating assets and liabilities:
(Increase) decrease in accrued interest receivable	14,192	(17,031)
Increase in other assets	(658)	(1,907)
Increase (decrease) in accrued interest payable	(3,691)	133
Increase (decrease) in accounts payable and other liabilities	842	(194)
Net cash provided by operating activities	294,677	312,888
Investing activities
Purchases of mortgage-backed securities	(8,521,002)	(15,160,173)
Principal repayments of mortgage-backed securities	4,823,759	3,978,718
Sale of mortgage-backed securities	8,027,113	2,678,086
Net cash provided by (used in) investing activities	4,329,869	(8,503,369)
Financing activities
Issuance of preferred stock		278,263
(Repurchase) issuance of common stock	(21,063)	587,677
Cash dividends paid	(223,978)	(227,297)
Increase (decrease) in restricted cash margin on derivatives	39,168	(65,166)
Net payment on termination of interest rate swap	(2,904)
Proceeds from repurchase agreements	186,080,168	170,030,964
Principal repayments on repurchase agreements	(190,116,826)	(162,610,159)
Net cash provided by (used in) financing activities	(4,245,435)	7,994,282
Net increase (decrease) in cash and cash equivalents	379,112	(196,199)
Cash and cash equivalents, beginning of period	168,424	347,045
Cash and cash equivalents, end of period	547,536	150,846
Supplemental disclosure of cash flow information
Cash paid during the period for interest	52,471	140,012
Supplemental schedule of non-cash investing activities
Obligation to brokers for purchase of unsettled mortgage-backed securities	986,828	1,527,972
Receivable for securities sold	548,942
Preferred Stock
Supplemental schedule of non-cash financing activities
Dividends declared, not yet paid	4,628	2,070
Common Stock Amount
Supplemental schedule of non-cash financing activities
Dividends declared, not yet paid	$ 53,850	$ 79,048