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Consolidated Condensed Schedule Of Investments (Long Investments) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended 12 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Schedule of Investments [Line Items]    
Fair Value $ 1,710,422 $ 1,375,116
Investment Owned, at Cost 1,675,134 1,328,153
Percentage collaterallized by GNRCMO certificates 100.00% 100.00%
Unrated But Agency-Guaranteed [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 146.99% 161.52%
Long Investment AAA Rating [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 0.00% 0.01%
Long Investment AA Rating [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 0.00% 0.26%
Long Investment A Rating [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 1.16% 1.02%
Long Investment BBB Rating [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 1.81% 3.70%
Long Investment BB Rating [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 113.82% 102.40%
Long Investment Unrated Rating [Member]
    
Schedule of Investments [Line Items]    
Long investment holdings as a percentage of stockholders' equity 3.90% 2.66%
Principal And Interest - Fixed Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 129.00% [1],[2],[3],[4] 148.21% [1],[2],[5],[6]
Fair Value 822,835 [2],[3],[4] 750,454 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 75,125 Federal National Mortgage Association Pool, 3.50% 2043-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 75,125 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-02 [2],[3],[4]  
Fair Value 75,620 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 39,607 Federal National Mortgage Association Pool, 3.50% 2043-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 39,607 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-01 [2],[3],[4]  
Fair Value 39,769 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 19,593 Federal National Mortgage Association Pool, 4.50% 2041-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 19,593 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-12 [2],[3],[4]  
Fair Value 20,895 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 16,806 Federal National Mortgage Association Pool, 4.50% 2041-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 16,806 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-09 [2],[3],[4]  
Fair Value 17,922 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 17,552 Federal National Mortgage Association Pool, 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 17,552 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-08 [2],[3],[4]  
Fair Value 17,846 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 16,329 Federal National Mortgage Association Pool, 5.00% 2041-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 16,329 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-08 [2],[3],[4]  
Fair Value 17,740 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 17,128 Federal National Mortgage Association Pool, 3.00% 2028-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 17,128 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2028-06 [2],[3],[4]  
Fair Value 17,574 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 16,033 Federal National Mortgage Association Pool, 4.50% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 16,033 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-10 [2],[3],[4]  
Fair Value 17,098 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 15,831 Federal Home Loan Mortgage Corporation Pool, 5.00% 2041-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 15,831 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-07 [2],[3],[4]  
Fair Value 17,076 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 13,767 Federal National Mortgage Association Pool, 5.00% 2041-03 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 13,767 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-03 [2],[3],[4]  
Fair Value 15,027 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 12,008 Federal National Mortgage Association Pool, 4.00% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 12,008 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-08 [2],[3],[4]  
Fair Value 12,523 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 12,607 Federal Home Loan Mortgage Corporation Pool, 3.00% 2042-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 12,607 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2042-10 [2],[3],[4]  
Fair Value 12,308 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 11,105 Federal National Mortgage Association Pool, 4.50% 2041-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 11,105 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-09 [2],[3],[4]  
Fair Value 11,775 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 11,076 Federal National Mortgage Association Pool, 4.00% 2041-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 11,076 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2041-11 [2],[3],[4]  
Fair Value 11,558 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 10,519 Federal National Mortgage Association Pool, 5.00% 2041-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 10,519 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-07 [2],[3],[4]  
Fair Value 11,480 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 9,995 Federal Home Loan Mortgage Corporation Pool, 4.00% 2043-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 9,995 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2043-07 [2],[3],[4]  
Fair Value 10,447 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 9,753 Federal National Mortgage Association Pool, 4.00% 2042-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 9,753 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-01 [2],[3],[4]  
Fair Value 10,177 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 9,853 Federal Home Loan Mortgage Corporation Pool, 3.00% 2043-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 9,853 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2043-02 [2],[3],[4]  
Fair Value 9,618 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 8,923 Federal Home Loan Mortgage Corporation Pool, 4.50% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 8,923 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-10 [2],[3],[4]  
Fair Value 9,454 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 8,372 Federal National Mortgage Association Pool, 4.50% 2026-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 8,372 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2026-04 [2],[3],[4]  
Fair Value 8,905 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 6,614 Federal National Mortgage Association Pool, 5.50% 2039-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 6,614 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.50% [2],[3],[4]  
Maturity 2039-10 [2],[3],[4]  
Fair Value 7,250 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 6,788 Federal Home Loan Mortgage Corporation Pool, 4.50% 2041-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 6,788 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-02 [2],[3],[4]  
Fair Value 7,203 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 6,480 Federal Home Loan Mortgage Corporation Pool, 3.00% 2043-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 6,480 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2043-01 [2],[3],[4]  
Fair Value 6,325 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 6,446 Federal Home Loan Mortgage Corporation Pool, 3.00% 2043-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 6,446 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2043-04 [2],[3],[4]  
Fair Value 6,291 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,593 Government National Mortgage Association Pool, 4.54% 2062-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,593 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.54% [2],[3],[4]  
Maturity 2062-11 [2],[3],[4]  
Fair Value 6,177 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,542 Government National Mortgage Association Pool, 4.46% 2063-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,542 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.46% [2],[3],[4]  
Maturity 2063-02 [2],[3],[4]  
Fair Value 6,108 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,965 Federal National Mortgage Association Pool, 3.50% 2043-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,965 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-05 [2],[3],[4]  
Fair Value 6,064 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,647 Federal National Mortgage Association Pool, 4.00% 2026-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,647 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2026-07 [2],[3],[4]  
Fair Value 5,955 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,385 Government National Mortgage Association Pool, 4.58% 2062-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,385 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.58% [2],[3],[4]  
Maturity 2062-10 [2],[3],[4]  
Fair Value 5,952 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,319 Government National Mortgage Association Pool, 4.52% 2063-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,319 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.52% [2],[3],[4]  
Maturity 2063-01 [2],[3],[4]  
Fair Value 5,875 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,771 Federal National Mortgage Association Pool, 3.50% 2043-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,771 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-06 [2],[3],[4]  
Fair Value 5,869 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,178 Government National Mortgage Association Pool, 4.60% 2062-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,178 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.60% [2],[3],[4]  
Maturity 2062-06 [2],[3],[4]  
Fair Value 5,718 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,157 Government National Mortgage Association Pool, 4.63% 2061-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,157 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.63% [2],[3],[4]  
Maturity 2061-06 [2],[3],[4]  
Fair Value 5,661 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,062 Federal National Mortgage Association Pool, 5.00% 2041-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,062 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-06 [2],[3],[4]  
Fair Value 5,474 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,252 Federal Home Loan Mortgage Corporation Pool, 4.00% 2042-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,252 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-05 [2],[3],[4]  
Fair Value 5,473 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,355 Federal National Mortgage Association Pool, 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,355 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-08 [2],[3],[4]  
Fair Value 5,444 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,034 Federal National Mortgage Association Pool, 4.00% 2042-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,034 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-04 [2],[3],[4]  
Fair Value 5,277 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,040 Federal National Mortgage Association Pool, 4.00% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,040 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2041-10 [2],[3],[4]  
Fair Value 5,260 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,023 Federal National Mortgage Association Pool, 3.50% 2043-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,023 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-06 [2],[3],[4]  
Fair Value 5,056 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,638 Federal National Mortgage Association Pool, 5.00% 2040-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,638 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2040-11 [2],[3],[4]  
Fair Value 5,038 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,624 Federal National Mortgage Association Pool, 5.00% 2041-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,624 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-07 [2],[3],[4]  
Fair Value 4,999 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,092 Federal Home Loan Mortgage Corporation Pool, 3.00% 2043-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,092 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2043-06 [2],[3],[4]  
Fair Value 4,970 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,658 Federal National Mortgage Association Pool, 4.50% 2041-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,658 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-08 [2],[3],[4]  
Fair Value 4,939 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,669 Federal National Mortgage Association Pool, 3.50% 2042-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,669 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-07 [2],[3],[4]  
Fair Value 4,747 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,730 Federal Home Loan Mortgage Corporation Pool, 3.00% 2043-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,730 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2043-02 [2],[3],[4]  
Fair Value 4,617 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,418 Federal Home Loan Mortgage Corporation Pool, 4.00% 2042-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,418 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-02 [2],[3],[4]  
Fair Value 4,605 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,465 Federal National Mortgage Association Pool, 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,465 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-11 [2],[3],[4]  
Fair Value 4,543 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,456 Federal National Mortgage Association Pool, 3.50% 2042-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,456 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-07 [2],[3],[4]  
Fair Value 4,528 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,173 Federal National Mortgage Association Pool, 4.00% 2042-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,173 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-09 [2],[3],[4]  
Fair Value 4,357 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,965 Federal National Mortgage Association Pool, 5.00% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,965 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2041-10 [2],[3],[4]  
Fair Value 4,280 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,267 Federal Home Loan Mortgage Corporation Pool, 3.50% 2043-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,267 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-06 [2],[3],[4]  
Fair Value 4,274 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,010 Federal National Mortgage Association Pool, 3.00% 2027-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 4,010 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2027-07 [2],[3],[4]  
Fair Value 4,129 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,886 Federal National Mortgage Association Pool, 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,886 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-08 [2],[3],[4]  
Fair Value 3,950 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,511 Federal National Mortgage Association Pool, 5.00% 2035-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,511 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2035-10 [2],[3],[4]  
Fair Value 3,834 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,439 Government National Mortgage Association Pool, 4.66% 2063-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,439 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.66% [2],[3],[4]  
Maturity 2063-01 [2],[3],[4]  
Fair Value 3,821 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,368 Government National Mortgage Association Pool, 4.80% 2061-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,368 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.80% [2],[3],[4]  
Maturity 2061-02 [2],[3],[4]  
Fair Value 3,698 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,300 Government National Mortgage Association Pool, 4.48% 2063-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,300 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.48% [2],[3],[4]  
Maturity 2063-02 [2],[3],[4]  
Fair Value 3,639 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,587 Federal Home Loan Mortgage Corporation Pool, 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,587 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-11 [2],[3],[4]  
Fair Value 3,637 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,453 Federal National Mortgage Association Pool, 4.00% 2026-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,453 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2026-06 [2],[3],[4]  
Fair Value 3,634 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,429 Federal National Mortgage Association Pool, 3.50% 2027-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,429 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2027-06 [2],[3],[4]  
Fair Value 3,581 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,483 Federal Home Loan Mortgage Corporation Pool, 3.00% 2028-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,483 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2028-06 [2],[3],[4]  
Fair Value 3,572 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,552 Federal Home Loan Mortgage Corporation Pool, 3.50% 2043-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,552 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-06 [2],[3],[4]  
Fair Value 3,566 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,387 Federal National Mortgage Association Pool, 4.00% 2042-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,387 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-04 [2],[3],[4]  
Fair Value 3,535 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,469 Federal National Mortgage Association Pool, 3.50% 2043-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,469 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-01 [2],[3],[4]  
Fair Value 3,529 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,229 Federal National Mortgage Association Pool, 5.00% 2040-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,229 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 5.00% [2],[3],[4]  
Maturity 2040-06 [2],[3],[4]  
Fair Value 3,514 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,292 Federal National Mortgage Association Pool, 4.50% 2042-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,292 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2042-04 [2],[3],[4]  
Fair Value 3,500 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,145 Government National Mortgage Association Pool, 4.68% 2061-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,145 [2],[3],[4]  
Description Government National Mortgage Association Pool [2],[3],[4]  
Rate 4.68% [2],[3],[4]  
Maturity 2061-10 [2],[3],[4]  
Fair Value 3,466 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,326 Federal National Mortgage Association Pool, 3.00% 2028-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,326 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2028-06 [2],[3],[4]  
Fair Value 3,430 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,338 Federal National Mortgage Association Pool, 3.00% 2028-03 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,338 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2028-03 [2],[3],[4]  
Fair Value 3,426 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,242 Federal National Mortgage Association Pool, 4.00% 2042-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,242 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-09 [2],[3],[4]  
Fair Value 3,385 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,170 Federal National Mortgage Association Pool, 4.50% 2041-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,170 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-12 [2],[3],[4]  
Fair Value 3,374 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,383 Federal Home Loan Mortgage Corporation Pool, 3.00% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,383 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2042-11 [2],[3],[4]  
Fair Value 3,301 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,162 Federal Home Loan Mortgage Corporation Pool, 4.00% 2042-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,162 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2042-01 [2],[3],[4]  
Fair Value 3,293 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,361 Federal Home Loan Mortgage Corporation Pool, 3.00% 2043-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,361 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2043-04 [2],[3],[4]  
Fair Value 3,281 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,228 Federal National Mortgage Association Pool, 3.50% 2042-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,228 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2042-12 [2],[3],[4]  
Fair Value 3,280 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,026 Federal Home Loan Mortgage Corporation Pool, 4.50% 2041-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,026 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation Pool [2],[3],[4]  
Rate 4.50% [2],[3],[4]  
Maturity 2041-09 [2],[3],[4]  
Fair Value 3,206 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,148 Federal National Mortgage Association Pool, 3.50% 2043-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,148 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 3.50% [2],[3],[4]  
Maturity 2043-05 [2],[3],[4]  
Fair Value 3,202 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Federal National Mortgage Association Pools [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 131,020 [2],[3],[4] 69,330 [2],[5],[6]
Description Other Federal National Mortgage Association Pools [2],[3],[4] Other Federal National Mortgage Association Pools [2],[5],[6]
Fair Value 136,057 [2],[3],[4] 74,508 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Federal National Mortgage Association Pools [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 6.00% [2],[3],[4] 6.00% [2],[5],[6]
Maturity 2043-07 [2],[3],[4] 2043-01 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Federal National Mortgage Association Pools [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 3.00% [2],[3],[4] 2.50% [2],[5],[6]
Maturity 2026-03 [2],[3],[4] 2026-03 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Federal Home Loan Mortgage Corporation Pools [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 45,976 [2],[3],[4] 19,340 [2],[5],[6]
Description Other Federal Home Loan Mortgage Corporation Pools [2],[3],[4] Other Federal Home Loan Mortgage Corporation Pools [2],[5],[6]
Fair Value 46,836 [2],[3],[4] 20,744 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Federal Home Loan Mortgage Corporation Pools [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 6.00% [2],[3],[4] 6.00% [2],[5],[6]
Maturity 2043-07 [2],[3],[4] 2042-12 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Federal Home Loan Mortgage Corporation Pools [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 3.00% [2],[3],[4] 3.50% [2],[5],[6]
Maturity 2026-04 [2],[3],[4] 2026-04 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Government National Mortgage Association Pools [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 13,609 [2],[3],[4]  
Description Other Government National Mortgage Association Pools [2],[3],[4]  
Fair Value 15,018 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Government National Mortgage Association Pools [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 4.69% [2],[3],[4]  
Maturity 2062-11 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | Other Government National Mortgage Association Pools [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 4.49% [2],[3],[4]  
Maturity 2061-07 [2],[3],[4]  
Principal And Interest - Fixed Rate Agency Securities [Member] | 49,427 Federal National Mortgage Association Pool, 3.50% 2042-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   49,427 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-12 [2],[5],[6]
Fair Value   52,864 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 45,304 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   45,304 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   48,596 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 35,601 Federal National Mortgage Association Pool 5.00% 2037-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   35,601 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2037-07 [2],[5],[6]
Fair Value   38,657 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 21,338 Federal National Mortgage Association Pool 4.50% 2041-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   21,338 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-12 [2],[5],[6]
Fair Value   23,268 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 18,227 Federal National Mortgage Association Pool 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   18,227 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   19,552 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 17,845 Federal National Mortgage Association Pool 4.50% 2041-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   17,845 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-09 [2],[5],[6]
Fair Value   19,459 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 17,634 Federal Home Loan Mortgage Corporation Pool 5.00% 2041-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   17,634 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-07 [2],[5],[6]
Fair Value   19,218 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 17,621 Federal National Mortgage Association Pool 5.00% 2041-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   17,621 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-08 [2],[5],[6]
Fair Value   19,201 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 17,113 Federal National Mortgage Association Pool 4.50% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   17,113 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-10 [2],[5],[6]
Fair Value   18,661 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 15,869 Federal National Mortgage Association Pool 5.00% 2041-03 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   15,869 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-03 [2],[5],[6]
Fair Value   17,430 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 14,911 Federal National Mortgage Association Pool 3.00% 2042-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   14,911 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2042-10 [2],[5],[6]
Fair Value   15,642 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 14,242 Federal National Mortgage Association Pool 4.00% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   14,242 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   15,407 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 13,519 Federal Home Loan Mortgage Corporation Pool 3.00% 2042-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   13,519 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2042-10 [2],[5],[6]
Fair Value   14,157 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 11,985 Federal National Mortgage Association Pool 4.50% 2041-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   11,985 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-09 [2],[5],[6]
Fair Value   12,994 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 11,942 Federal National Mortgage Association Pool 4.00% 2041-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   11,942 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2041-11 [2],[5],[6]
Fair Value   12,848 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 11,003 Federal National Mortgage Association Pool 5.00% 2041-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   11,003 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-07 [2],[5],[6]
Fair Value   12,058 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 10,576 Federal National Mortgage Association Pool 4.00% 2042-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   10,576 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-01 [2],[5],[6]
Fair Value   11,355 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 9,576 Federal National Mortgage Association Pool 4.50% 2026-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   9,576 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2026-04 [2],[5],[6]
Fair Value   10,338 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 9,002 Federal Home Loan Mortgage Corporation Pool 4.50% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   9,002 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-10 [2],[5],[6]
Fair Value   9,772 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 8,321 Federal Home Loan Mortgage Corporation Pool 4.50% 2041-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   8,321 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-02 [2],[5],[6]
Fair Value   9,038 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 7,395 Federal National Mortgage Association Pool 5.50% 2039-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   7,395 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.50% [2],[5],[6]
Maturity   2039-10 [2],[5],[6]
Fair Value   8,075 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 7,428 Eight Federal National Mortgage Association Pool 3.50% 2042-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   7,428 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-10 [2],[5],[6]
Fair Value   7,984 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 7,352 Federal National Mortgage Association Pool 4.00% 2026-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   7,352 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2026-07 [2],[5],[6]
Fair Value   7,888 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 6,324 Federal National Mortgage Association Pool 5.00% 2041-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   6,324 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-06 [2],[5],[6]
Fair Value   6,891 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,929 Federal National Mortgage Association Pool 3.50% 2042-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,929 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-05 [2],[5],[6]
Fair Value   6,356 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,689 Federal Home Loan Mortgage Corporation Pool 4.00% 2042-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,689 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-05 [2],[5],[6]
Fair Value   6,141 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,592 Federal National Mortgage Association Pool 4.00% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,592 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2041-10 [2],[5],[6]
Fair Value   6,079 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,642 Federal National Mortgage Association Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,642 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   6,020 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,494 Federal National Association Pool 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,494 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   5,862 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,085 Federal National Mortgage Association Pool 5.00% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,085 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-10 [2],[5],[6]
Fair Value   5,534 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,085 Federal National Mortgage Association Pool 4.00% 2042-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,085 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-04 [2],[5],[6]
Fair Value   5,531 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,045 Federal National Mortgage Association Pool 5.00% 2040-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,045 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2040-11 [2],[5],[6]
Fair Value   5,497 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 5,025 Federal National Mortgage Association Pool 5.00% 2041-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,025 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2041-07 [2],[5],[6]
Fair Value   5,444 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,944 Federal National Mortgage Association Pool 4.50% 2041-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,944 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-08 [2],[5],[6]
Fair Value   5,361 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,911 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,911 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-09 [2],[5],[6]
Fair Value   5,242 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,676 Federal National Mortgage Association Pool 4.00% 2042-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,676 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-09 [2],[5],[6]
Fair Value   5,059 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,725 Federal National Mortgage Association Pool 3.50% 2042-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,725 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-07 [2],[5],[6]
Fair Value   5,042 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,699 Federal National Mortgage Association Pool 4.00% 2026-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,699 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2026-06 [2],[5],[6]
Fair Value   5,041 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,513 Federal National Mortgage Association Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,513 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   4,828 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,465 Federal Home Loan Mortgage Corporation Pool 4.00% 2042-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,465 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-02 [2],[5],[6]
Fair Value   4,787 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,456 Federal National Mortgage Association Pool 3.00% 2027-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,456 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2027-07 [2],[5],[6]
Fair Value   4,710 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,261 Federal National Mortgage Association Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,261 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   4,573 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 4,009 Federal Home Loan Mortgage Corporation Pool 4.00% 2041-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,009 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2041-11 [2],[5],[6]
Fair Value   4,303 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,964 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,964 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   4,229 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,926 Federal National Mortgage Association Pool 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,926 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   4,189 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,798 Federal National Mortgage Association Pool 5.00% 2035-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,798 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2035-10 [2],[5],[6]
Fair Value   4,172 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,864 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,864 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-10 [2],[5],[6]
Fair Value   4,116 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,728 Federal National Mortgage Association Pool 5.00% 2040-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,728 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.00% [2],[5],[6]
Maturity   2040-06 [2],[5],[6]
Fair Value   4,062 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,726 Federal National Mortgage Association Pool 4.50% 2041-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,726 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-12 [2],[5],[6]
Fair Value   4,040 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,763 Federal National Mortgage Association Pool 3.50% 2027-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,763 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2027-06 [2],[5],[6]
Fair Value   4,022 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,766 Federal National Mortgage Association Pool 3.00% 2027-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,766 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2027-08 [2],[5],[6]
Fair Value   3,980 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,606 Federal National Mortgage Association Pool 4.50% 2042-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,606 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2042-04 [2],[5],[6]
Fair Value   3,941 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,526 Federal Home Loan Mortgage Corporation Pool 6.00% 2039-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,526 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   6.00% [2],[5],[6]
Maturity   2039-04 [2],[5],[6]
Fair Value   3,848 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,534 Federal National Mortgage Association Pool 3.50% 2042-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,534 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-12 [2],[5],[6]
Fair Value   3,770 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,442 Federal Home Loan Mortgage Corporation Pool 4.50% 2041-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,442 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-09 [2],[5],[6]
Fair Value   3,737 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,483 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,483 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   3,712 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,419 Federal National Mortgage Association Pool 4.00% 2042-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,419 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-04 [2],[5],[6]
Fair Value   3,706 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,404 Federal Home Loan Mortgage Corporation Pool 4.00% 2042-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,404 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-01 [2],[5],[6]
Fair Value   3,653 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,344 Federal National Mortgage Association Pool 4.00% 2042-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,344 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-09 [2],[5],[6]
Fair Value   3,618 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,415 Federal Home Loan Mortgage Corporation Pool 3.00% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,415 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   3,573 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,288 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-02 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,288 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-02 [2],[5],[6]
Fair Value   3,518 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,182 Federal National Mortgage Association Pool 4.00% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,182 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   3,440 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,095 Federal National Mortgage Association Pool 4.50% 2041-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,095 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-11 [2],[5],[6]
Fair Value   3,355 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 3,053 Federal National Mortgage Association Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   3,053 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   3,262 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,931 Federal National Mortgage Association Pool 4.00% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,931 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   3,178 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,947 Federal National Mortgage Association Pool 3.50% 2027-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,947 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2027-07 [2],[5],[6]
Fair Value   3,145 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,921 Federal National Mortgage Association Pool 3.50% 2027-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,921 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2027-06 [2],[5],[6]
Fair Value   3,123 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,828 Federal National Mortgage Association Pool 4.50% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,828 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-10 [2],[5],[6]
Fair Value   3,076 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,605 Government National Mortgage Association 4.55% 2062-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,605 [2],[5],[6]
Description   Government National Mortgage Association [2],[5],[6]
Rate   4.55% [2],[5],[6]
Maturity   2062-10 [2],[5],[6]
Fair Value   2,977 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,676 Federal National Mortgage Association Pool 4.50% 2041-10 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,676 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2041-10 [2],[5],[6]
Fair Value   2,901 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,566 Federal National Mortgage Association Pool 4.00% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,566 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   2,774 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,490 Federal National Mortgage Association Pool 4.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,490 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.50% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   2,719 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,497 Federal National Mortgage Association Pool 4.00% 2042-09 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,497 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-09 [2],[5],[6]
Fair Value   2,699 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,519 Federal National Mortgage Association Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,519 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   2,690 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,520 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,520 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   2,685 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,498 Federal National Mortgage Association Pool 3.50% 2042-08 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,498 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-08 [2],[5],[6]
Fair Value   2,679 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,500 Federal Home Loan Mortgage Corporation Pool 3.50% 2042-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,500 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-01 [2],[5],[6]
Fair Value   2,667 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,452 Federal National Mortgage Association Pool 3.50% 2042-11 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,452 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.50% [2],[5],[6]
Maturity   2042-11 [2],[5],[6]
Fair Value   2,619 [2],[5],[6]
Principal And Interest - Fixed Rate Agency Securities [Member] | 2,377 Federal National Mortgage Association Pool 4.00% 2042-06 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,377 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2042-06 [2],[5],[6]
Fair Value   2,564 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 1.98% [1],[2],[3],[4] 0.64% [1],[2],[5],[6]
Fair Value 12,613 [2],[3],[4] 3,250 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Federal National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 53,465 [2],[3],[4] 20,095 [2],[5],[6]
Description Other Federal National Mortgage Association [2],[3],[4] Other Federal National Mortgage Association [2],[5],[6]
Fair Value 6,177 [2],[3],[4] 1,920 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Federal National Mortgage Association [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 5.50% [2],[3],[4] 5.50% [2],[5],[6]
Maturity 2043-04 [2],[3],[4] 2040-10 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Federal National Mortgage Association [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 3.00% [2],[3],[4] 4.00% [2],[5],[6]
Maturity 2020-12 [2],[3],[4] 2036-01 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Federal Home Loan Mortgage Corporation [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 24,264 [2],[3],[4] 10,426 [2],[5],[6]
Description Other Federal Home Loan Mortgage Corporation [2],[3],[4] Other Federal Home Loan Mortgage Corporation [2],[5],[6]
Fair Value 3,393 [2],[3],[4] 1,195 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Federal Home Loan Mortgage Corporation [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 5.50% [2],[3],[4] 5.50% [2],[5],[6]
Maturity 2043-01 [2],[3],[4] 2039-01 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Federal Home Loan Mortgage Corporation [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 3.00% [2],[3],[4] 5.00% [2],[5],[6]
Maturity 2032-12 [2],[3],[4] 2033-06 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Government National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 22,552 [2],[3],[4] 4,269 [2],[5],[6]
Description Other Government National Mortgage Association [2],[3],[4] Other Government National Mortgage Association [2],[5],[6]
Rate   5.50% [2],[5],[6]
Maturity   2036-03 [2],[5],[6]
Fair Value 3,043 [2],[3],[4] 135 [2],[5],[6]
Interest Only - Fixed Rate Agency Securities [Member] | Other Government National Mortgage Association [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 5.50% [2],[3],[4]  
Maturity 2042-11 [2],[3],[4]  
Interest Only - Fixed Rate Agency Securities [Member] | Other Government National Mortgage Association [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 3.00% [2],[3],[4]  
Maturity 2036-03 [2],[3],[4]  
TBA - Fixed Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 12.69% [1],[2],[3],[4] 8.61% [1],[2],[5],[6]
Fair Value 80,959 [2],[3],[4] 43,610 [2],[5],[6]
TBA - Fixed Rate Agency Securities [Member] | 65,800 Federal Home Loan Mortgage Corporation (30 Year) 3.00% 2013-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 65,800 [2],[3],[4]  
Description Federal Home Loan Mortgage Corporation (30 Year) [2],[3],[4]  
Rate 3.00% [2],[3],[4]  
Maturity 2013-07 [2],[3],[4]  
Fair Value 64,135 [2],[3],[4]  
TBA - Fixed Rate Agency Securities [Member] | 15,570 Federal National Mortgage Association (30 Year) 4.00% 2013-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 15,570 [2],[3],[4]  
Description Federal National Mortgage Association (30 Year) [2],[3],[4]  
Rate 4.00% [2],[3],[4]  
Maturity 2013-07 [2],[3],[4]  
Fair Value 16,221 [2],[3],[4]  
TBA - Fixed Rate Agency Securities [Member] | 600 Other Federal National Mortgage Association (15 Year) 2.50% 2013-07 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 600 [2],[3],[4]  
Description Other Federal National Mortgage Association (15 Year) [2],[3],[4]  
Rate 2.50% [2],[3],[4]  
Maturity 2013-07 [2],[3],[4]  
Fair Value 603 [2],[3],[4]  
TBA - Fixed Rate Agency Securities [Member] | 18,950 Federal Home Loan Mortgage Corporation (30 Years) 4.00% 2013-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   18,950 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation (30 Year) [2],[5],[6]
Rate   4.00% [2],[5],[6]
Maturity   2013-01 [2],[5],[6]
Fair Value   20,232 [2],[5],[6]
TBA - Fixed Rate Agency Securities [Member] | 16,600 Federal National Mortgage Association (15 Years) 3.00% 2013-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   16,600 [2],[5],[6]
Description   Federal National Mortgage Association (15 Year) [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2013-01 [2],[5],[6]
Fair Value   17,523 [2],[5],[6]
TBA - Fixed Rate Agency Securities [Member] | 5,600 Federal Home Loan Mortgage Corporation (30 Years) 3.00% 2013-01 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   5,600 [2],[5],[6]
Description   Federal Home Loan Mortgage Corporation (30 Year) [2],[5],[6]
Rate   3.00% [2],[5],[6]
Maturity   2013-01 [2],[5],[6]
Fair Value   5,855 [2],[5],[6]
Fixed Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 143.67% [1],[2],[3],[4] 157.46% [1],[2],[5],[6]
Fair Value 916,407 [2],[3],[4] 797,314 [2],[5],[6]
Investment Owned, at Cost 938,872 [2],[3],[4] 789,964 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 1.63% [1],[2],[3],[4] 3.39% [1],[2],[5],[6]
Fair Value 10,425 [2],[3],[4] 17,169 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member] | Other Federal National Mortgage Association Pools [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 2,851 [2],[3],[4] 3,159 [2],[5],[6]
Description Other Federal National Mortgage Association Pools [2],[3],[4] Other Federal National Mortgage Association Pools [2],[5],[6]
Fair Value 3,013 [2],[3],[4] 3,385 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member] | Other Federal National Mortgage Association Pools [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 4.93% [2],[3],[4] 5.50% [2],[5],[6]
Maturity 2037-09 [2],[3],[4] 2037-09 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member] | Other Federal National Mortgage Association Pools [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 2.69% [2],[3],[4] 4.93% [2],[5],[6]
Maturity 2036-04 [2],[3],[4] 2037-07 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member] | 3,804 Federal National Mortgage Association Pool 2.53% 2038-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,804 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 2.53% [2],[3],[4]  
Maturity 2038-05 [2],[3],[4]  
Fair Value 4,005 [2],[3],[4]  
Principal And Interest - Floating Rate Agency Securities [Member] | 3,243 Federal National Mortgage Association Pool 2.55% 2035-12 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 3,243 [2],[3],[4]  
Description Federal National Mortgage Association Pool [2],[3],[4]  
Rate 2.55% [2],[3],[4]  
Maturity 2035-12 [2],[3],[4]  
Fair Value 3,407 [2],[3],[4]  
Principal And Interest - Floating Rate Agency Securities [Member] | 6,045 Federal National Mortgage Association Pool 5.08% 2038-05 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   6,045 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.08% [2],[5],[6]
Maturity   2038-05 [2],[5],[6]
Fair Value   6,374 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member] | 4,537 Federal National Mortgage Association Pool 3.14% 2035-15 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   4,537 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   3.14% [2],[5],[6]
Maturity   2035-12 [2],[5],[6]
Fair Value   4,783 [2],[5],[6]
Principal And Interest - Floating Rate Agency Securities [Member] | 2,478 Federal National Mortgage Association Pool 5.69% 2036-04 [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount   2,478 [2],[5],[6]
Description   Federal National Mortgage Association Pool [2],[5],[6]
Rate   5.69% [2],[5],[6]
Maturity   2036-04 [2],[5],[6]
Fair Value   2,627 [2],[5],[6]
Interest Only - Floating Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 2.32% [1],[2],[3],[4] 0.67% [1],[2],[5],[6]
Fair Value 14,784 [2],[3],[4] 3,394 [2],[5],[6]
Interest Only - Floating Rate Agency Securities [Member] | Other Federal National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 31,510 [2],[3],[4] 1,042 [2],[5],[6]
Description Other Federal National Mortgage Association [2],[3],[4] Other Federal National Mortgage Association [2],[5],[6]
Rate   5.50% [2],[5],[6]
Maturity   2036-08 [2],[5],[6]
Fair Value 5,865 [2],[3],[4] 152 [2],[5],[6]
Interest Only - Floating Rate Agency Securities [Member] | Other Federal National Mortgage Association [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 6.56% [2],[3],[4]  
Maturity 2043-02 [2],[3],[4]  
Interest Only - Floating Rate Agency Securities [Member] | Other Federal National Mortgage Association [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 5.50% [2],[3],[4]  
Maturity 2036-08 [2],[3],[4]  
Interest Only - Floating Rate Agency Securities [Member] | Other Government National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 46,845 [2],[3],[4]  
Description Other Government National Mortgage Association [2],[3],[4]  
Fair Value 6,165 [2],[3],[4]  
Interest Only - Floating Rate Agency Securities [Member] | Other Government National Mortgage Association [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 6.56% [2],[3],[4]  
Maturity 2061-04 [2],[3],[4]  
Interest Only - Floating Rate Agency Securities [Member] | Other Government National Mortgage Association [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 2.58% [2],[3],[4]  
Maturity 2042-11 [2],[3],[4]  
Interest Only - Floating Rate Agency Securities [Member] | Resecuritization of Government National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 23,104 [2],[3],[4],[7] 23,140 [2],[5],[6],[7]
Description Resecuritization of Government National Mortgage Association (q) [2],[3],[4],[7] Resecuritization of Government National Mortgage Association (o) [2],[5],[6],[7]
Rate 4.28% [2],[3],[4],[7] 4.28% [2],[5],[6],[7]
Maturity 2060-08 [2],[3],[4],[7] 2060-08 [2],[5],[6],[7]
Fair Value 2,754 [2],[3],[4],[7] 3,242 [2],[5],[6],[7]
Floating Rate Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 3.95% [1],[2],[3],[4] 4.06% [1],[2],[5],[6]
Fair Value 25,209 [2],[3],[4] 20,563 [2],[5],[6]
Investment Owned, at Cost 25,535 [2],[3],[4] 19,979 [2],[5],[6]
Agency Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 147.62% [1],[2],[3],[4] 161.52% [1],[2],[5],[6]
Fair Value 941,616 [2],[3],[4] 817,877 [2],[5],[6]
Investment Owned, at Cost 964,407 [2],[3],[4] 809,943 [2],[5],[6]
Principal And Interest - Private Label Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 112.06% [1],[2],[3] 107.47% [1],[2],[5]
Fair Value 714,797 [2],[3] 544,208 [2],[5]
Investment Owned, at Cost 656,261 [2],[3] 505,380 [2],[5]
Principal And Interest - Private Label Securities [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 989,570 [2],[3] 850,320 [2],[5]
Description Various [2],[3] Various [2],[5]
Fair Value 714,797 [2],[3] 544,208 [2],[5]
Principal And Interest - Private Label Securities [Member] | Various Issuer [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 9.35% [2],[3] 9.35% [2],[5]
Maturity 2047-06 [2],[3] 2047-05 [2],[5]
Principal And Interest - Private Label Securities [Member] | Various Issuer [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 0.28% [2],[3] 0.17% [2],[5]
Maturity 2019-05 [2],[3] 2019-05 [2],[5]
Principal Only - Private Label Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 0.39% [1],[2],[3] 0.46% [1],[5]
Fair Value 2,466 [2],[3] 2,320 [2],[5]
Investment Owned, at Cost 2,355 [2],[3] 2,242 [2],[5]
Principal Only - Private Label Securities [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 5,800 [2],[3] 5,800 [2],[5]
Description Various [2],[3] Various [2],[5]
Rate 0.00% [2],[3] 0.00% [2],[5]
Maturity 2030-08 [2],[3] 2030-08 [2],[5]
Fair Value 2,466 [2],[3] 2,320 [2],[5]
Interest Only - Private Label Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 0.18% [1],[2],[3] 0.23% [1],[2],[5]
Fair Value 1,153 [2],[3] 1,165 [2],[5]
Investment Owned, at Cost 569 [2],[3] 637 [2],[5]
Interest Only - Private Label Securities [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 54,772 [2],[3] 61,640 [2],[5]
Description Various [2],[3] Various [2],[5]
Fair Value 1,153 [2],[3] 1,165 [2],[5]
Interest Only - Private Label Securities [Member] | Various Issuer [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 2.00% [2],[3] 2.00% [2],[5]
Maturity 2047-09 [2],[3] 2047-09 [2],[5]
Interest Only - Private Label Securities [Member] | Various Issuer [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 0.50% [2],[3] 0.50% [2],[5]
Maturity 2044-06 [2],[3] 2044-06 [2],[5]
Other Private Label Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 0.00% [1],[2],[3] 0.00% [1],[2],[5]
Fair Value 0 [2],[3] 0 [2],[5]
Investment Owned, at Cost 370 [2],[3] 429 [2],[5]
Other Private Label Securities [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 136,465 [2],[3] 158,348 [2],[5]
Description Various [2],[3] Various [2],[5]
Rate 0.00% [2],[3] 0.00% [2],[5]
Maturity 2037-06 [2],[3] 2037-06 [2],[5]
Fair Value 0 [2],[3] 0 [2],[5]
Private Label Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 112.63% [1],[2],[3] 108.16% [1],[2],[5]
Fair Value 718,416 [2],[3] 547,693 [2],[5]
Investment Owned, at Cost 659,555 [2],[3] 508,688 [2],[5]
Mortgage-Backed Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 260.25% [1],[2],[3] 269.68% [1],[2],[5]
Fair Value 1,660,032 [2],[3] 1,365,570 [2],[5]
Investment Owned, at Cost 1,623,962 [2],[3] 1,318,631 [2],[5]
Asset-backed Securities [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 6.25% [1],[2],[3]  
Fair Value 39,840 [2],[3]  
Investment Owned, at Cost 40,767 [2],[3]  
Asset-backed Securities [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 43,432 [2],[3]  
Description Various [2],[3]  
Fair Value 39,840 [2],[3]  
Asset-backed Securities [Member] | Various Issuer [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 9.78% [2],[3]  
Maturity 2049-12 [2],[3]  
Asset-backed Securities [Member] | Various Issuer [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 0.00% [2],[3]  
Maturity 2017-06 [2],[3]  
Commercial Mortgage Loans [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 1.18% [1],[2],[3],[8] 1.89% [1],[2],[5],[9]
Fair Value 7,563 [2],[3],[8] 9,546 [2],[5],[9]
Investment Owned, at Cost 7,453 [2],[3],[8] 9,522 [2],[5],[9]
Commercial Mortgage Loans [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Current Principal/Notional Amount 9,041 [2],[3],[8] 10,225 [2],[5],[9]
Description Various [2],[3],[8] Various [2],[5],[9]
Fair Value 7,563 [2],[3],[8] 9,546 [2],[5],[9]
Commercial Mortgage Loans [Member] | Various Issuer [Member] | Maximum [Member]
    
Schedule of Investments [Line Items]    
Rate 7.25% [2],[3] 6.25% [2],[5],[9]
Maturity 2014-06 [2],[3] 2039-05 [2],[5],[9]
Commercial Mortgage Loans [Member] | Various Issuer [Member] | Minimum [Member]
    
Schedule of Investments [Line Items]    
Rate 0.00% [2],[3] 5.00% [2],[5],[9]
Maturity 2013-11 [2],[3] 2013-11 [2],[5],[9]
Common Stocks, by Industry [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 0.47% [1],[2],[3]  
Fair Value 2,987 [2],[3]  
Investment Owned, at Cost 2,952 [2],[3]  
Common Stocks, by Industry [Member] | Real Estate Investment Trusts [Member]
    
Schedule of Investments [Line Items]    
Description Publicly Traded Real Estate Investment Trusts [2],[3]  
Fair Value 2,987 [2],[3]  
Investment Owned, Balance, Shares 130 [2],[3]  
Long Investments [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 268.15% [1],[2],[3] 271.57% [1],[2],[5]
Fair Value 1,710,422 [2],[3] 1,375,116 [2],[5]
Investment Owned, at Cost 1,675,134 [2],[3] 1,328,153 [2],[5]
Long Investments [Member] | Federal National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 97.77% 119.78%
Long Investments [Member] | Federal Home Loan Mortgage Corporation [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 37.76% 40.49%
Long Investments [Member] | Government National Mortgage Association [Member]
    
Schedule of Investments [Line Items]    
Investment owned as a percentage of net assets 12.09% 1.25%
Commercial Mortgage Loan With Extendable Maturity [Member] | Commercial Mortgage Loans [Member] | Various Issuer [Member]
    
Schedule of Investments [Line Items]    
Fair Value $ 5,000 $ 4,900
[1] Classification percentages are based on Total Equity.
[2] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.
[3] The table below shows the ratings on the Company's long investments, excluding common stock, from Moody's, Standard and Poor's, or Fitch, as well as the Company's long investments that were unrated but affiliated with Fannie Mae, Freddie Mac, or Ginnie Mae. Ratings tend to be a lagging credit indicator; as a result, the credit quality of the Company's long investment holdings may be lower than the credit quality implied based on the ratings listed below. In situations where an investment has a split rating, the lowest provided rating is used. The ratings descriptions include ratings qualified with a "+," "-," "1," "2," or "3."Rating Description Percent ofEquityUnrated but Agency-Guaranteed 146.99%Aaa/AAA/AAA 0.00%Aa/AA/AA 0.00%A/A/A 1.16%Baa/BBB/BBB 1.81%Ba/BB/BB or below 113.82%Unrated 3.90%
[4] At June 30, 2013, the Company's long investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association represented 97.77%, 37.76%, and 12.09% of equity, respectively.
[5] The table below shows the Company's long investment ratings from Moody's, Standard and Poor's, or Fitch, as well as the Company's long investments that were unrated but affiliated with Fannie Mae, Freddie Mac, or Ginnie Mae. Ratings tend to be a lagging credit indicator; as a result, the credit quality of the Company's long investment holdings may be lower than the credit quality implied based on the ratings listed below. In situations where an investment has a split rating, the lowest provided rating is used. The ratings descriptions include ratings qualified with a "+," "-," "1," "2," or "3."Rating Description Percent ofEquityUnrated but Agency-Guaranteed 161.52%Aaa/AAA/AAA 0.01%Aa/AA/AA 0.26%A/A/A 1.02%Baa/BBB/BBB 3.70%Ba/BB/BB or below 102.40%Unrated 2.66%
[6] At December 31, 2012, the Company’s long investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association represented 119.78%, 40.49%, and 1.25% of equity, respectively.
[7] Private trust 100% backed by interest in Government National Mortgage Association collateralized mortgage obligation certificates.
[8] Includes a loan with a fair value in the amount of $5.0 million where the maturity date may be extended through November 4, 2015 as well as a non-performing commercial whole loan.
[9] Includes a loan with a fair value in the amount of $4.9 million where the maturity date may be extended through November 4, 2015 as well as a non-performing commercial whole loan.