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Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy) (Details) (USD $) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2011 | Jun. 30, 2010 | Jun. 30, 2011 | Jun. 30, 2010 | Dec. 31, 2010
Carrying Value | $ 132,137,000 |  | $ 132,137,000 |  | $ 137,865,000
Remaining Commitment | 61,620,000 |  | 61,620,000 |  |
Decrease in other investments |  |  | (5,700,000) |  |
Net investment income earned | 39,345,000 | 36,545,000 | 82,818,000 | 71,251,000 |
Energy/Power Generation [Member] | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 29,862,000 |  | 29,862,000 |  | 35,560,000
Remaining Commitment | 10,296,000 |  | 10,296,000 |  |
Net investment income earned | 1,284,000 | 965,000 | 5,839,000 | 3,031,000 |
Secondary Private Equity Member | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 27,601,000 |  | 27,601,000 |  | 26,709,000
Remaining Commitment | 12,334,000 |  | 12,334,000 |  |
Net investment income earned | 3,067,000 | 2,665,000 | 4,716,000 | 3,684,000 |
Distressed Debt [Member] | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 19,868,000 |  | 19,868,000 |  | 20,432,000
Remaining Commitment | 3,389,000 |  | 3,389,000 |  |
Net investment income earned | 421,000 | (41,000) | 1,394,000 | 723,000 |
Private Equity [Member] | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 18,786,000 |  | 18,786,000 |  | 21,601,000
Remaining Commitment | 7,966,000 |  | 7,966,000 |  |
Net investment income earned | 1,181,000 | 99,000 | 3,758,000 | 807,000 |
Real Estate Strategy [Member] | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 15,642,000 |  | 15,642,000 |  | 14,192,000
Remaining Commitment | 10,670,000 |  | 10,670,000 |  |
Net investment income earned | 681,000 | (494,000) | 1,450,000 | (2,359,000) |
Mezzanine Financing [Member] | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 10,126,000 |  | 10,126,000 |  | 10,230,000
Remaining Commitment | 15,865,000 |  | 15,865,000 |  |
Net investment income earned | 701,000 | 1,692,000 | 1,061,000 | 2,629,000 |
Venture Capital [Member] | Alternative Investments [Member] |  |  |  |  |
Carrying Value | 7,666,000 |  | 7,666,000 |  | 6,386,000
Remaining Commitment | 1,100,000 |  | 1,100,000 |  |
Net investment income earned | 565,000 | (18,000) | 1,323,000 | 248,000 |
Other Securities [Member] |  |  |  |  |
Carrying Value | 2,586,000 |  | 2,586,000 |  | 2,755,000
Remaining Commitment | 0 |  | 0 |  |
Other Investments [Member] |  |  |  |  |
Net investment income earned | 7,922,000 | 4,884,000 | 19,588,000 | 8,816,000 |
Alternative Investments [Member] |  |  |  |  |
Carrying Value | 129,551,000 |  | 129,551,000 |  | 135,110,000
Remaining Commitment | 61,620,000 |  | 61,620,000 |  |
Distributions from alternative investments |  |  | 32,800,000 |  |
Contributions under existing commitments |  |  | $ 7,700,000 |  |

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- Definition This item represents disclosure of the amount of distributions received from alternative investments. These investments are accounted for under the equity method of accounting. + Details
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- Definition This item represents the amount of funding that the company has provided for the alternative investments portfolio for the period. + Details
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- Definition The income earned from investments in securities and other investments including dividends, interest, and returns on other investments. This item does not include realized gains (losses). + Details
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- Definition Other investments not otherwise specified in the taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 12 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph g -Article 7 + Details
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