Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS:
NET INCREASE IN SHAREHOLDERS' EQUITY RESULTING FROM OPERATIONS	$ 32,055	$ 11,107
Reconciliation of the net increase in shareholders' equity resulting from operations to net cash used in operating activities:
Change in net unrealized (gain) loss on investments and financial derivatives	(32,884)	11,095
Net realized (gain) loss on investments and financial derivatives	11,789	(11,604)
Amortization of premiums and accretion of discounts (net)	(2,346)	(2,721)
Purchase of investments	(827,052)	(966,316)
Proceeds from disposition of investments	814,756	879,456
Proceeds from principal payments of investments	29,722	23,898
Proceeds from investments sold short	566,348	983,292
Repurchase of investments sold short	(450,793)	(1,016,337)
Payments made to open financial derivatives	(40,628)	(29,424)
Proceeds received to close financial derivatives	41,907	66,611
Proceeds received to open financial derivatives	21,564	7,963
Payments made to close financial derivatives	(18,952)	(14,134)
Shares issued in connection with incentive fee payment		142
Share-based LTIP expense	28	38
(Increase) decrease in assets:
(Increase) decrease in repurchase agreements	2,100	(14,441)
Increase in receivable for securities sold	(108,510)	(158,678)
(Increase) decrease in deposits with dealers held as collateral	1,801	(1,477)
(Increase) decrease in interest and principal receivable	(11)	450
Increase in other assets	(828)	(489)
Increase (decrease) in liabilities:
Decrease in due to brokers on margin accounts	(14,238)	(31,821)
Increase (decrease) in payable for securities purchased	(56,829)	166,776
Increase (decrease) in accounts payable and accrued expenses	(323)	570
Increase (decrease) in incentive fee payable		470
Increase in interest and dividends payable	94	260
Increase in base management fee payable	96	1,481
Net cash used in operating activities	(31,134)	(93,833)
Cash flows provided by (used in) financing activities:
Offering costs paid		(134)
Dividends paid	(6,735)	(22,126)
Proceeds from issuance of securitized debt	1,522
Principal payments on securitized debt	(40)
Reverse repurchase agreements, net of repayments	25,196	121,742
Net cash provided by financing activities	19,943	99,482
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(11,191)	5,649
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	62,737	35,791
CASH AND CASH EQUIVALENTS, END OF PERIOD	51,546	41,440
Supplemental disclosure of cash flow information:
Interest paid	1,727	1,283
Shares issued in connection with incentive fee payment (non-cash)		142
Share-based LTIP awards (non-cash)	28	38
Aggregate TBA trade activity (buys + sells) (non-cash)	$ 4,179,427	$ 5,633,198