Statements Of Assets And Liabilities (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
ASSETS:
Investments in securities, at fair value (including net pledged assets of $8,412,295 and $3,671,582, respectively)	$ 9,466,128	$ 6,331,048
Interest rate swap contracts, at fair value		9,113
Interest rate cap contracts, at fair value	5,966	30,984
Cash and cash equivalents	11,508	1,510
Receivable for securities sold	5,550
Interest receivable	27,815	16,183
Other assets	1,090	429
Total assets	9,518,057	6,389,267
LIABILITIES:
Repurchase agreements	7,880,814	3,443,843
Interest rate swap contracts, at fair value	79,476	9,757
Payable for securities purchased	463,302	2,234,401
Accrued interest payable (including accrued interest on repurchase agreements of $3,747 and $1,084, respectively)	15,617	9,412
Related party management fee payable		800
Accrued expenses and other liabilities	1,390	715
Total liabilities	8,440,599	5,698,928
Contingencies (note 11)
NET ASSETS	1,077,458	690,339
Net assets consist of:
Common Stock, $0.01 par value, 500,000 shares authorized (82,753 and 59,551 shares issued and outstanding, respectively)	828	596
Additional paid in capital	997,884	739,005
Retained earnings (Accumulated deficit)	78,746	(49,262)
NET ASSETS	$ 1,077,458	$ 690,339
NET ASSET VALUE PER SHARE	$ 13.02	$ 11.59