Statements Of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Interest income:
Interest income on mortgage-backed securities	$ 424,713	$ 263,751	$ 282,344
Interest income on short-term cash investments	1,407	1,265	771
Interest income	426,120	265,016	283,115
Interest expense	144,662	95,923	96,267
Net interest income	281,458	169,093	186,848
Operating expenses:
Management fee	13,787	9,205	8,677
Share based compensation	1,150	1,432	1,296
General and administrative	2,724	2,507	2,475
Total operating expenses	17,661	13,144	12,448
Other income/(expense):
Net gain on sale of mortgage-backed securities	20,576	13,551
Other income/(expense)	20,576	13,551
Net income	$ 284,373	$ 169,500	$ 174,400
Earnings per share - common stock, basic and diluted	$ 3.97	$ 4.30	$ 4.82
Weighted average shares outstanding	71,708,058	39,454,362	36,195,840