CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Interest Income:
Interest income	$ 36,576	$ 68,776	$ 139,926	$ 197,718
Interest expense	(2,281)	(3,149)	(7,080)	(9,160)
Net interest income (expense)	110,340	152,789	363,204	433,321
Other-than-temporary impairments:
Total other-than-temporary impairment losses	(2,713)	(78,950)	(47,264)	(161,924)
Portion of loss recognized in other comprehensive income (loss)	(7,301)	(71,610)	(76,801)	(83,989)
Net other-than-temporary credit impairment losses	(10,014)	(150,560)	(124,065)	(245,913)
Other gains (losses):
Net unrealized gains (losses) on interest rate swaps	(4,427)	(25,312)	(14,607)	(34,981)
Net realized gains (losses) on interest rate swaps	(5,298)	(4,500)	(14,890)	(11,644)
Net gains (losses) on interest rate swaps	(9,725)	(29,812)	(29,497)	(46,625)
Net unrealized gains (losses) on interest-only RMBS	(15,393)	(17,600)	22	(1,611)
Net realized gains (losses) on sales of investments	69,155	58	85,165	1,787
Total other gains (losses)	44,037	(47,354)	55,690	(46,449)
Net investment income (loss)	144,363	(45,125)	294,829	140,959
Other expenses:
Management fees	13,051	13,252	38,863	39,154
Expense recoveries from Manager	(1,910)		(1,910)
Net Management fees	11,141	13,252	36,953	39,154
Provision for loan losses, net	496		(396)	1,442
General and administrative expenses	4,658	1,830	9,188	5,137
Total other expenses	16,295	15,082	45,745	45,733
Income (loss) before income taxes	128,068	(60,207)	249,084	95,226
Income taxes		(171)	2	645
Net income (loss)	128,068	(60,036)	249,082	94,581
Net income (loss) per share available to common shareholders:
Basic	$ 0.12	$ (0.06)	$ 0.24	$ 0.09
Diluted	$ 0.12	$ (0.06)	$ 0.24	$ 0.09
Weighted average number of common shares outstanding:
Basic	1,026,841,087	1,026,404,030	1,026,804,427	1,026,308,073
Diluted	1,027,505,030	1,027,195,404	1,027,499,973	1,027,130,136
Dividends declared per share of common stock	$ 0.09	$ 0.13	$ 0.29	$ 0.40
Comprehensive income (loss):
Net income (loss)	128,068	(60,036)	249,082	94,581
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale securities, net	260,891	(41,863)	380,004	(258,253)
Reclassification adjustment for net losses included in net income (loss) for other-than-temporary credit impairment losses	10,014	150,560	124,065	245,913
Reclassification adjustment for net realized losses (gains) included in net income (loss)	(69,155)	(58)	(85,165)	(1,787)
Other comprehensive income (loss)	201,750	108,639	418,904	(14,127)
Comprehensive income (loss)	329,818	48,603	667,986	80,454
Variable Interest Entities, Primary Beneficiary, Aggregated Disclosure [Member] | Non Agency Residential Mortgage Backed Securities And Securitized Loans [Member]
Net Interest Income:
Interest income, Assets of consolidated VIEs	108,120	116,805	315,962	339,765
Interest expense, Non-recourse liabilities of consolidated VIEs	$ (32,075)	$ (29,643)	$ (85,604)	$ (95,002)