Consolidated Condensed Schedule Of Investments (Investments Sold Short) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Investments Sold, Not yet Purchased [Line Items]
Investments sold short at fair value-	$ (608,922)		$ (622,301)
Proceeds from investments sold short	(614,208)		(621,048)
TBA - Fixed Rate Agency Securities Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short at fair value-	(561,845)	[1],[2]	(608,720)	[1],[3]
Proceeds from investments sold short	(566,128)	[1],[2]	(607,967)	[1],[3]
Investments sold not yet purchased as a percentage of net assets	(88.08%)	[1],[2],[4]	(120.22%)	[1],[3],[4]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(193,482)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	3.50%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(196,437)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(77,380)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	4.50%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(81,893)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(61,400)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	5.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(66,091)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(42,160)	[1],[2]
Description	Federal National Mortgage Association (15 Year)	[1],[2]
Rate	3.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(43,369)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 2013-08 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(40,400)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	3.50%	[1],[2]
Investments maturity date	2013-08	[1],[2]
Investments sold short at fair value-	(40,900)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(27,950)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	3.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(27,320)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 3.50% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(20,100)	[1],[2]
Description	Federal Home Loan Mortgage Corporation (30 Year)	[1],[2]
Rate	3.50%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(20,356)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 5.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(16,500)	[1],[2]
Description	Federal Home Loan Mortgage Corporation (30 Year)	[1],[2]
Rate	5.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(17,621)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.50% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(15,800)	[1],[2]
Description	Federal National Mortgage Association (15 Year)	[1],[2]
Rate	3.50%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(16,475)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(14,104)	[1],[2]
Description	Federal National Mortgage Association (15 Year)	[1],[2]
Rate	4.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(14,869)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.50% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(11,000)	[1],[2]
Description	Federal National Mortgage Association (15 Year)	[1],[2]
Rate	4.50%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(11,656)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(9,200)	[1],[2]
Description	Federal Home Loan Mortgage Corporation (30 Year)	[1],[2]
Rate	4.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(9,564)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% 2013-08 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(7,400)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	4.00%	[1],[2]
Investments maturity date	2013-08	[1],[2]
Investments sold short at fair value-	(7,689)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.50% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(3,500)	[1],[2]
Description	Federal National Mortgage Association (30 Year)	[1],[2]
Rate	5.50%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(3,801)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal National Mortgage Association (30 Year) 6.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(2,500)	[1],[2]
Description	Other Federal National Mortgage Association (30 Year)	[1],[2]
Rate	6.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(2,720)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal Home Loan Mortgage Corporation (30 Year) 6.00% 2013-07 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(1,000)	[1],[2]
Description	Other Federal Home Loan Mortgage Corporation (30 Year)	[1],[2]
Rate	6.00%	[1],[2]
Investments maturity date	2013-07	[1],[2]
Investments sold short at fair value-	(1,084)	[1],[2]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(198,168)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			3.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(211,343)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(87,500)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			5.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(94,794)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(77,730)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			4.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(83,982)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 3.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(53,400)	[1],[3]
Description			Federal Home Loan Mortgage Corporation (30 Year)	[1],[3]
Rate			3.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(56,804)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(34,510)	[1],[3]
Description			Federal National Mortgage Association (15 Year)	[1],[3]
Rate			3.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(36,430)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(31,600)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			3.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(33,128)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 5.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(16,500)	[1],[3]
Description			Federal Home Loan Mortgage Corporation (30 Year)	[1],[3]
Rate			5.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(17,776)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(16,450)	[1],[3]
Description			Federal National Mortgage Association (15 Year)	[1],[3]
Rate			3.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(17,460)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(15,718)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			4.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(16,852)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(14,104)	[1],[3]
Description			Federal National Mortgage Association (15 Year)	[1],[3]
Rate			4.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(15,096)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(11,000)	[1],[3]
Description			Federal National Mortgage Association (15 Year)	[1],[3]
Rate			4.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(11,833)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(7,500)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			5.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(8,148)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 6.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(2,500)	[1],[3]
Description			Federal National Mortgage Association (30 Year)	[1],[3]
Rate			6.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(2,731)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal National Mortgage Association (15 Year) 2.50% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(1,200)	[1],[3]
Description			Other Federal National Mortgage Association (15 Year)	[1],[3]
Rate			2.50%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(1,255)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal Home Loan Mortgage Corporation (30 Year) 6.00% 2013-01 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount			(1,000)	[1],[3]
Description			Other Federal Home Loan Mortgage Corporation (30 Year)	[1],[3]
Rate			6.00%	[1],[3]
Investments maturity date			2013-01	[1],[3]
Investments sold short at fair value-			(1,088)	[1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold not yet purchased as a percentage of net assets	(80.46%)		(105.27%)
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold not yet purchased as a percentage of net assets	(7.62%)		(14.95%)
U.S. Treasury Securities Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short at fair value-	(40,977)	[1]	(13,581)	[1]
Proceeds from investments sold short	(41,929)	[1]	(13,081)	[1]
Investments sold not yet purchased as a percentage of net assets	(6.42%)	[1],[4]	(2.68%)	[1],[4]
U.S. Treasury Securities Sold Short [Member] | U.S. Treasury Note 2.00% 2023-02 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(18,700)	[1]
Description	U.S. Treasury Note	[1]
Rate	2.00%	[1]
Investments maturity date	2023-02	[1]
Investments sold short at fair value-	(17,989)	[1]
U.S. Treasury Securities Sold Short [Member] | U.S. Treasury Note 1.75% 2016-05 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(13,000)	[1]	(13,000)	[1]
Description	U.S. Treasury Note	[1]	U.S. Treasury Note	[1]
Rate	1.75%	[1]	1.75%	[1]
Investments maturity date	2016-05	[1]	2016-05	[1]
Investments sold short at fair value-	(13,408)	[1]	(13,581)	[1]
U.S. Treasury Securities Sold Short [Member] | U.S. Treasury Note 1.13% 2019-02 [Member]
Investments Sold, Not yet Purchased [Line Items]
Current Principal/Notional Amount	(10,000)	[1]
Description	U.S. Treasury Note	[1]
Rate	1.13%	[1]
Investments maturity date	2019-12	[1]
Investments sold short at fair value-	(9,580)	[1]
Common Stock Sold Short [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short at fair value-	(6,100)	[1]
Proceeds from investments sold short	(6,151)	[1]
Investments sold not yet purchased as a percentage of net assets	(0.96%)	[1],[4]
Common Stock Sold Short [Member] | Real Estate Investment Trusts [Member]
Investments Sold, Not yet Purchased [Line Items]
Description	Publicly Traded Real Estate Investment Trusts	[1]
Investments sold short at fair value-	(6,100)	[1]
Investment Sold, Not yet Purchased, Balance, Shares	(439)	[1]
Securities Sold Short - Securities Sold, Not Yet Purchased [Member]
Investments Sold, Not yet Purchased [Line Items]
Investments sold short at fair value-	(608,922)	[1]	(622,301)	[1]
Proceeds from investments sold short	$ (614,208)	[1]	$ (621,048)	[1]
Investments sold not yet purchased as a percentage of net assets	(95.46%)	[1],[4]	(122.90%)	[1],[4]

[1] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.

[2] At June 30, 2013, the Company's short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation represented 80.46% and 7.62% of equity, respectively.

[3] At December 31, 2012, the Company’s short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation represented 105.27% and 14.95% of equity, respectively.

[4] Classification percentages are based on Total Equity.