Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS:
NET INCREASE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS	$ 97,146		$ 10,327		$ 40,571
Reconciliation of the net increase in shareholders’ equity resulting from operations to net cash provided by (used in) operating activities:
Change in net unrealized (gain) loss on investments and financial derivatives	(84,206)		61,199		9,377
Net realized (gain) loss on investments and financial derivatives	11,247		(26,831)		(25,161)
Amortization of premiums and accretion of discounts (net)	(13,010)		(9,012)		(6,643)
Purchase of investments	(2,345,880)		(3,510,693)		(2,738,252)
Proceeds from disposition of investments	2,166,238		3,456,869		2,193,660
Proceeds from principal payments of investments	142,617		105,974		111,279
Proceeds from investments sold short	938,699		903,545		814,444
Repurchase of investments sold short	(796,974)		(1,254,648)		(563,798)
Payments made to open financial derivatives	(91,019)		(150,437)		(310,677)
Proceeds received to close financial derivatives	126,207		255,346		211,160
Proceeds received to open financial derivatives	42,920		27,209		81,754
Payments made to close financial derivatives	(56,948)		(33,213)		(65,882)
Shares issued in connection with incentive fee payment	1,180		203		528
Share-based LTIP expense	135		147		1,987
(Increase) decrease in assets:
(Increase) decrease in repurchase agreements	2,100		9,934		(25,684)
(Increase) decrease in receivable for securities sold	(93,211)		265,434		(285,321)
(Increase) decrease in deposits with dealers held as collateral	11,419		(13,769)		2,677
(Increase) decrease in interest and principal receivable	408		(218)		3,389
Increase in other assets	(111)		0		0
Increase (decrease) in liabilities:
Increase (decrease) in due to brokers on margin accounts	(48,781)		(86,674)		59,926
Increase (decrease) in payable for securities purchased	(70,184)		(56,496)		142,368
Increase (decrease) in accounts payable and accrued expenses	98		(239)		1,101
Increase (decrease) in incentive fee payable	7,343		(1,422)		(853)
Increase in other payables	903		0		0
Increase (decrease) in interest and dividends payable	(270)		141		113
Increase (decrease) in base management fee payable	538		(129)		388
Net cash used in operating activities	(51,396)		(47,453)		(347,549)
Cash flows provided by financing activities:
Net proceeds from the issuance of shares(1)	88,142	[1]	0	[1]	98,310	[1]
Shares repurchased	(3,430)		(1,051)		0
Offering costs paid	(323)		(618)		(1,709)
Dividends paid	(47,412)		(42,382)		(33,906)
Proceeds from issuance of securitized debt	1,522		0		0
Principal payments on securitized debt	(264)		0		0
Reverse repurchase agreements, net of repayments	9,508		118,450		217,782
Net cash provided by financing activities	47,743		74,399		280,477
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(3,653)		26,946		(67,072)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	62,737		35,791		102,863
CASH AND CASH EQUIVALENTS, END OF PERIOD	59,084		62,737		35,791
Supplemental disclosure of cash flow information:
Interest paid	8,040		6,600		3,631
Shares issued in connection with incentive fee payment (non-cash)	1,180		203		528
Share-based LTIP awards (non-cash)	135		147		1,987
Aggregate TBA trade activity (buys sells) (non-cash)	$ 16,365,027		$ 21,558,273		$ 16,071,356

[1] Proceeds from the issuance of shares are net of underwriters’ discount in the amount of $1,852 and $2,940 for the years ended December 31, 2012 and 2010, respectively.