Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities
Net income (loss)	$ (134,136)	$ 349,245	$ 284,373
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net amortization of premium related to mortgage-backed securities	165,924	162,844	93,335
Reclassification of deferred swap loss	25,816
Amortization related to interest rate swap agreements	311	361	346
Share based compensation expense	2,594	1,920	1,150
Hedge ineffectiveness	(205)	178	655
Net (gain) loss on sale of mortgage-backed securities	283,012	(64,347)	(20,576)
Impairment loss on mortgage-backed securities	8,102
Net loss on derivative instruments	68,205
Changes in operating assets and liabilities:
(Increase) decrease in accrued interest receivable	21,957	(14,088)	(25,052)
Increase in other assets	(2,432)	(191)	(1,881)
Increase in accrued interest payable	687	2,996	1,419
Increase in accounts payable and other liabilities	572	110	1,111
Net cash provided by operating activities	440,407	439,028	334,880
Investing activities
Purchases of mortgage-backed securities	(10,180,894)	(17,988,431)	(13,351,128)
Principal repayments of mortgage-backed securities	5,782,709	5,635,988	3,559,612
Sale of mortgage-backed securities	11,280,146	4,518,105	1,766,557
Net payments on derivative instruments	(67,656)
Net cash provided by (used in) investing activities	6,814,305	(7,834,338)	(8,024,959)
Financing activities
Issuance of preferred stock		278,252
(Repurchase) issuance of common stock	(43,881)	587,657	860,602
Cash dividends paid	(283,309)	(309,267)	(255,827)
Proceeds from repurchase agreements	226,824,755	231,718,347	163,847,236
Principal repayments on repurchase agreements	(233,561,501)	(225,014,293)	(156,365,921)
Proceeds from dollar roll liability	1,784,998
Repayments on dollar roll liability	(1,433,172)
Increase (decrease) in restricted cash margin on derivatives	55,642	(44,007)	(161,592)
Payment on termination interest rate swap	(3,342)
Net cash provided by (used in) financing activities	(6,659,810)	7,216,689	7,924,498
Net increase (decrease) in cash and cash equivalents	594,902	(178,621)	234,419
Cash and cash equivalents, beginning of period	168,424	347,045	112,626
Cash and cash equivalents, end of period	763,326	168,424	347,045
Supplemental disclosure of cash flow information
Cash paid during the period for interest	197,022	194,068	143,243
Supplemental schedule of non-cash investing activities
Obligation to brokers for purchase of unsettled mortgage-backed securities		722,221	397,936
Receivable for securities sold	231,214	1,587,535
Supplemental schedule of non-cash financing activities
Dividends declared, not yet paid	52,929	73,804
Preferred Stock
Supplemental schedule of non-cash financing activities
Dividends declared, not yet paid	4,628	4,628
Common Stock Amount
Supplemental schedule of non-cash financing activities
Dividends declared, not yet paid	$ 48,301	$ 69,176	$ 69,141