v2.4.0.6
Consolidated Condensed Schedule Of Investments (Investments Sold Short) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended 12 Months Ended
Sep. 30, 2012
Dec. 31, 2011
Investments Sold, Not yet Purchased [Line Items]    
Fair value $ (456,824) $ (462,394)
Proceeds from investments sold short (455,057) (459,013)
Securities Sold Short - Securities Sold, Not Yet Purchased [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Fair value (456,824) [1] (462,394) [1]
Proceeds from investments sold short (455,057) [1] (459,013) [1]
Investments sold not yet purchased as a percentage of net assets (91.61%) [1] (124.66%) [1]
U.S. Treasury Securities Sold Short [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Fair value (13,633) [1] (15,687) [1]
Proceeds from investments sold short (13,087) [1] (15,120) [1]
Investments sold not yet purchased as a percentage of net assets (2.73%) [1] (4.23%) [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] (15,000) [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]
Fair value (13,633) [1] (15,687) [1]
TBA - Fixed Rate Agency Securities Sold Short [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Fair value (443,191) [1],[2] (446,707) [1],[3]
Proceeds from investments sold short (441,970) [1],[2] (443,893) [1],[3]
Investments sold not yet purchased as a percentage of net assets (88.88%) [1],[2] (120.43%) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.00% 2012-11 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (60,700) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 5.00% [1],[2]  
Investments maturity date 2012-11 [1],[2]  
Fair value (66,180) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (59,352) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 3.50% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (63,650) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 3.50% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (45,200) [1],[2]  
Description Federal Home Loan Mortgage Corporation (30 Year) [1],[2]  
Rate 3.50% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (48,467) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% 2012-11 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (40,100) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 4.50% [1],[2]  
Investments maturity date 2012-11 [1],[2]  
Fair value (43,388) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 2012-11 [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 2012-11 [1],[2]  
Fair value (43,215) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (33,130) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 4.50% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (35,866) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.00% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (17,600) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 5.00% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (19,198) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 5.00% 2012-10 [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 2012-10 [1],[2]  
Fair value (17,883) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.00% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (16,300) [1],[2]  
Description Federal National Mortgage Association (15 Year) [1],[2]  
Rate 4.00% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (17,428) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.00% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (15,900) [1],[2]  
Description Federal National Mortgage Association (15 Year) [1],[2]  
Rate 3.00% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (16,856) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% 2012-11 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (14,600) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 4.00% [1],[2]  
Investments maturity date 2012-11 [1],[2]  
Fair value (15,714) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.50% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (13,500) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 5.50% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (14,802) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 3.50% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (12,300) [1],[2]  
Description Federal National Mortgage Association (15 Year) [1],[2]  
Rate 3.50% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (13,090) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.50% 2012-10 [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 2012-10 [1],[2]  
Fair value (11,863) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.00% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (9,918) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 4.00% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (10,687) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 6.00% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (2,500) [1],[2]  
Description Federal National Mortgage Association (30 Year) [1],[2]  
Rate 6.00% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (2,761) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal Home Loan Mortgage Corporation (30 Year) 6.00% 2012-10 [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 2012-10 [1],[2]  
Fair value (1,099) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal Home Loan Mortgage Corporation (15 Year) 3.00% 2012-10 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount (989) [1],[2]  
Description Other Federal Home Loan Mortgage Corporation (15 Year) [1],[2]  
Rate 3.00% [1],[2]  
Investments maturity date 2012-10 [1],[2]  
Fair value (1,044) [1],[2]  
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 4.50% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (147,700) [1],[3]
Description   Federal National Mortgage Association (30 Year) [1],[3]
Rate   4.50% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (157,185) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.00% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (114,200) [1],[3]
Description   Federal National Mortgage Association (30 Year) [1],[3]
Rate   5.00% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (123,376) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 5.00% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (31,000) [1],[3]
Description   Federal Home Loan Mortgage Corporation (30 Year) [1],[3]
Rate   5.00% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (33,316) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 4.50% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (30,400) [1],[3]
Description   Federal Home Loan Mortgage Corporation (30 Year) [1],[3]
Rate   4.50% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (32,217) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association (30 Year) 5.00% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (26,000) [1],[3]
Description   Government National Mortgage Association (30 Year) [1],[3]
Rate   5.00% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (28,805) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.00% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (25,300) [1],[3]
Description   Federal National Mortgage Association (15 Year) [1],[3]
Rate   4.00% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (26,688) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 5.50% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (13,500) [1],[3]
Description   Federal National Mortgage Association (30 Year) [1],[3]
Rate   5.50% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (14,700) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (15 Year) 4.50% 2012-01 [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   2012-01 [1],[3]
Fair value   (11,727) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 3.50% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (8,400) [1],[3]
Description   Federal National Mortgage Association (30 Year) [1],[3]
Rate   3.50% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (8,640) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal Home Loan Mortgage Corporation (30 Year) 3.50% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (4,400) [1],[3]
Description   Federal Home Loan Mortgage Corporation (30 Year) [1],[3]
Rate   3.50% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (4,517) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Federal National Mortgage Association (30 Year) 6.00% 2012-01 [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   2012-01 [1],[3]
Fair value   (2,753) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Government National Mortgage Association (30 Year) 5.50% 2012-01 [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Current Principal/Notional Amount   (1,500) [1],[3]
Description   Other Government National Mortgage Association (30 Year) [1],[3]
Rate   5.50% [1],[3]
Investments maturity date   2012-01 [1],[3]
Fair value   (1,685) [1],[3]
TBA - Fixed Rate Agency Securities Sold Short [Member] | Other Federal Home Loan Mortgage Corporation (30 Year) 6.00% 2012-01 [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   2012-01 [1],[3]
Fair value   $ (1,098) [1],[3]
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 13.74% 19.18%
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 75.14% 93.03%
TBA - Fixed Rate Agency Securities Sold Short [Member] | Government National Mortgage Association [Member]
    
Investments Sold, Not yet Purchased [Line Items]    
Investments sold not yet purchased as a percentage of net assets   8.22%
[1] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.
[2] At September 30, 2012, the Company's short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation represented 75.14% and 13.74% of shareholders' equity, respectively.
[3] At December 31, 2011, the Company's short investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association represented 93.03%, 19.18%, and 8.22% of shareholders' equity, respectively.