Consolidated Condensed Schedule Of Investments (Financial Derivatives) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013 contracts		Dec. 31, 2012 contracts
Investment Holdings, Other than Securities [Line Items]
Derivative Assets	$ 36,250,000		$ 48,504,000
Fair Value	(18,490,000)		(15,212,000)
Financial derivatives - assets, cost	56,769,000		65,860,000
Financial derivatives - liabilities, proceeds	(14,358,000)		(13,171,000)
Futures [Member]
Investment Holdings, Other than Securities [Line Items]
Future contract notional	1,000,000		1,000,000
Future contract	1		1
Financial Derivatives - Assets [Member]
Investment Holdings, Other than Securities [Line Items]
Derivative Assets	36,250,000	[1],[2]	48,504,000	[1],[2]
Investment owned as a percentage of net assets	6.96%	[1],[3]	9.58%	[1],[3]
Financial derivatives - assets, cost	56,769,000	[1]	65,860,000	[1]
Financial Derivatives - Assets [Member] | Long Credit Default Swap On Asset Backed Indices [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Credit	[1],[4]	Credit	[1],[4]
Notional value	2,285,000	[1],[4]	10,166,000	[1],[4]
Range of expiration dates	2037-12	[1],[4]
Derivative Assets	78,000	[1],[4]	765,000	[1],[4]
Financial derivatives - assets, cost			135,000	[1],[4]
Financial derivatives - liabilities, proceeds	(217,000)	[1],[4]
Financial Derivatives - Assets [Member] | Long Credit Default Swap On Asset Backed Indices [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates			2036-06	[1],[4]
Financial Derivatives - Assets [Member] | Long Credit Default Swap On Asset Backed Indices [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates			2037-12	[1],[4]
Financial Derivatives - Assets [Member] | Long Interest Rate Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Interest Rates	[1],[5]
Notional value	5,460,000	[1],[5]
Derivative Assets	6,000	[1],[5]
Financial Derivatives - Assets [Member] | Long Interest Rate Swaps [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2018-03	[1],[5]
Financial Derivatives - Assets [Member] | Long Interest Rate Swaps [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2023-03	[1],[5]
Financial Derivatives - Assets [Member] | Long Total Return Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Equity Market	[1],[6]
Notional value	1,264,000	[1],[6]
Range of expiration dates	2018-03	[1],[6]
Derivative Assets	7,000	[1],[6]
Financial Derivatives - Assets [Member] | Short Credit Default Swap On Asset Backed Securities [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Credit	[1],[7]	Credit	[1],[7]
Notional value	(32,571,000)	[1],[7]	(42,121,000)	[1],[7]
Derivative Assets	26,398,000	[1],[7]	36,031,000	[1],[7]
Financial Derivatives - Assets [Member] | Short Credit Default Swap On Asset Backed Securities [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2034-11	[1],[7]	2034-09	[1],[7]
Financial Derivatives - Assets [Member] | Short Credit Default Swap On Asset Backed Securities [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2036-05	[1],[7]	2036-05	[1],[7]
Financial Derivatives - Assets [Member] | Short Credit Default Swap On Asset Backed Indices [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Credit	[1],[8]	Credit	[1],[8]
Notional value	(57,451,000)	[1],[8]	(66,829,000)	[1],[8]
Derivative Assets	9,329,000	[1],[8]	11,703,000	[1],[8]
Financial Derivatives - Assets [Member] | Short Credit Default Swap On Asset Backed Indices [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2046-05	[1],[8]	2046-05	[1],[8]
Financial Derivatives - Assets [Member] | Short Credit Default Swap On Asset Backed Indices [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2063-05	[1],[8]	2052-10	[1],[8]
Financial Derivatives - Assets [Member] | Short Interest Rate Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Interest Rates	[1],[9]	Interest Rates	[1],[9]
Notional value	(152,050,000)	[1],[9]	(18,900,000)	[1],[9]
Range of expiration dates			2017-10	[1],[9]
Derivative Assets	378,000	[1],[9]	5,000	[1],[9]
Financial Derivatives - Assets [Member] | Short Interest Rate Swaps [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2015-03	[1],[9]
Financial Derivatives - Assets [Member] | Short Interest Rate Swaps [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2023-04	[1],[9]
Financial Derivatives - Assets [Member] | Short Total Return Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Equity Market	[1],[6]
Notional value	(6,396,000)	[1],[6]
Derivative Assets	54,000	[1],[6]
Financial Derivatives - Assets [Member] | Short Total Return Swaps [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2013-09	[1],[6]
Financial Derivatives - Assets [Member] | Short Total Return Swaps [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2018-03	[1],[6]
Financial Derivatives - Assets [Member] | Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Derivative Assets	36,250,000	[1]	48,504,000	[1]
Investment owned as a percentage of net assets	6.96%	[1],[3]	9.58%	[1],[3]
Financial derivatives - assets, cost	56,769,000	[1]	65,860,000	[1]
Financial Derivatives - Assets [Member] | Futures [Member]
Investment Holdings, Other than Securities [Line Items]
Investment owned as a percentage of net assets			(0.01%)	[1],[3]
Financial Derivatives - Liabilities [Member]
Investment Holdings, Other than Securities [Line Items]
Fair Value	(18,490,000)	[1],[2]	(15,212,000)	[1],[2]
Investment owned as a percentage of net assets	(3.55%)	[1],[3]	(3.00%)	[1],[3]
Financial derivatives - liabilities, proceeds	(14,358,000)	[1]	(13,171,000)	[1]
Financial Derivatives - Liabilities [Member] | Long Credit Default Swap On Asset Backed Indices [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Credit	[1],[4]	Credit	[1],[4]
Notional value	37,650,000	[1],[4]	30,050,000	[1],[4]
Fair Value	(14,170,000)	[1],[4]	(12,751,000)	[1],[4]
Financial derivatives - liabilities, proceeds	(14,125,000)	[1],[4]	(12,736,000)	[1],[4]
Financial Derivatives - Liabilities [Member] | Long Credit Default Swap On Asset Backed Indices [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2049-12	[1],[4]	2049-12	[1],[4]
Financial Derivatives - Liabilities [Member] | Long Credit Default Swap On Asset Backed Indices [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2063-05	[1],[4]	2051-02	[1],[4]
Financial Derivatives - Liabilities [Member] | Long Interest Rate Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Interest Rates	[1],[5]	Interest Rates	[1],[5]
Notional value	11,820,000	[1],[5]	2,500,000	[1],[5]
Fair Value	(23,000)	[1],[5]	(32,000)	[1],[5]
Financial Derivatives - Liabilities [Member] | Long Interest Rate Swaps [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2015-03	[1],[5]	2022-11	[1],[5]
Financial Derivatives - Liabilities [Member] | Long Interest Rate Swaps [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2023-03	[1],[5]	2022-12	[1],[5]
Financial Derivatives - Liabilities [Member] | Long Total Return Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Equity Market	[1],[6]
Notional value	1,176,000	[1],[6]
Range of expiration dates	2018-03	[1],[6]
Fair Value	(20,000)	[1],[6]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swap On Asset Backed Securities [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Credit	[1],[7]	Credit	[1],[7]
Notional value	(4,691,000)	[1],[7]	(3,000,000)	[1],[7]
Range of expiration dates			2035-03	[1],[7]
Fair Value	(2,000)	[1],[7]	(1,000)	[1],[7]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swap On Asset Backed Securities [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2034-09	[1],[7]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swap On Asset Backed Securities [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2035-03	[1],[7]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swap On Asset Backed Indices [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure			Credit	[1],[8]
Notional value			(7,792,000)	[1],[8]
Fair Value			(717,000)	[1],[8]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swap On Asset Backed Indices [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates			2036-06	[1],[8]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swap On Asset Backed Indices [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates			2037-12	[1],[8]
Financial Derivatives - Liabilities [Member] | Short Credit Default Swaps On Corporate Bond Indices [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Credit	[1],[10]	Credit	[1],[10]
Notional value	(85,500,000)	[1],[10]	(67,500,000)	[1],[10]
Range of expiration dates	2018-06	[1],[10]	2017-12	[1],[10]
Fair Value	(2,759,000)	[1],[10]	(484,000)	[1],[10]
Financial Derivatives - Liabilities [Member] | Short Interest Rate Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Interest Rates	[1],[9]	Interest Rates	[1],[9]
Notional value	(396,020,000)	[1],[9]	(220,000,000)	[1],[9]
Fair Value	(1,461,000)	[1],[9]	(1,092,000)	[1],[9]
Financial Derivatives - Liabilities [Member] | Short Interest Rate Swaps [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2014-12	[1],[9]	2014-08	[1],[9]
Financial Derivatives - Liabilities [Member] | Short Interest Rate Swaps [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2023-03	[1],[9]	2022-11	[1],[9]
Financial Derivatives - Liabilities [Member] | Short Total Return Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Equity Market	[1],[6]	Equity Market	[1],[6]
Notional value	(7,175,000)	[1],[6]	(18,737,000)	[1],[6]
Range of expiration dates			2013-09	[1],[6]
Fair Value	(7,000)	[1],[6]	(65,000)	[1],[6]
Financial Derivatives - Liabilities [Member] | Short Total Return Swaps [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2013-09	[1],[6]
Financial Derivatives - Liabilities [Member] | Short Total Return Swaps [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2018-03	[1],[6]
Financial Derivatives - Liabilities [Member] | Swaps [Member]
Investment Holdings, Other than Securities [Line Items]
Fair Value	(18,442,000)	[1]	(15,142,000)	[1]
Investment owned as a percentage of net assets	(3.54%)	[1],[3]	(2.99%)	[1],[3]
Financial derivatives - liabilities, proceeds	(14,358,000)	[1]	(13,171,000)	[1]
Financial Derivatives - Liabilities [Member] | Short Eurodollar Future [Member]
Investment Holdings, Other than Securities [Line Items]
Primary risk exposure	Interest Rates	[1],[11]	Interest Rates	[1],[11]
Notional value	(42,000,000)	[1],[11]	(63,000,000)	[1],[11]
Fair Value	(48,000)	[1],[11]	(70,000)	[1],[11]
Financial Derivatives - Liabilities [Member] | Short Eurodollar Future [Member] | Minimum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2013-06	[1],[11]	2013-03	[1],[11]
Financial Derivatives - Liabilities [Member] | Short Eurodollar Future [Member] | Maximum [Member]
Investment Holdings, Other than Securities [Line Items]
Range of expiration dates	2013-09	[1],[11]	2013-09	[1],[11]
Financial Derivatives - Liabilities [Member] | Futures [Member]
Investment Holdings, Other than Securities [Line Items]
Fair Value	$ (48,000)	[1]	$ (70,000)	[1]
Investment owned as a percentage of net assets	(0.01%)	[1],[3]

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

[2] In the Company’s Consolidated Statement of Assets, Liabilities, and Equity, all balances associated with the repurchase agreements, reverse repurchase agreements, and derivatives transactions are presented on a gross basis.

[3] Classification percentages are based on Total Equity.

[4] For long credit default swaps on asset-backed indices, the Company sold protection.

[5] For long interest rate swap contracts, a floating rate is being paid and a fixed rate is being received.

[6] Notional value represents number of underlying shares or par value times the closing price of the underlying security.

[7] For short credit default swaps on asset-backed securities, the Company purchased protection.

[8] For short credit default swaps on asset-backed indices, the Company purchased protection.

[9] For short interest rate swap contracts, a fixed rate is being paid and a floating rate is being received.

[10] For short credit default swaps on corporate bond indices, the Company purchased protection.

[11] Every $1,000,000 in notional value represents one contract.