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Investments (Aggregated Income Statement Summarized Financial Information for Partnerhips in our Alternative Investment Portfolio) (Details) (USD $) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2014 | Sep. 30, 2013
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Net investment income earned | $ 34,292,000 |  | $ 32,457,000 |  | $ 106,600,000 |  | $ 99,330,000 |
Alternative Investments [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Net investment income earned | 3,900,000 | [1] | 2,600,000 | [1] | 12,700,000 | [2] | 10,100,000 | [2]
Investments accounted for under the equity method [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Net Investment Income | 81,300,000 | [1] | 97,800,000 | [1] | 167,000,000 | [2] | 352,800,000 | [2]
Realized gains | (26,100,000) | [1] | 162,800,000 | [1] | 171,500,000 | [2] | 762,500,000 | [2]
Net change in unrealized appreciation (depreciation) | 628,600,000 | [1] | 104,800,000 | [1] | 1,471,000,000 | [2] | 85,900,000 | [2]
Net income | $ 683,800,000 | [1] | $ 365,400,000 | [1] | $ 1,809,500,000 | [2] | $ 1,201,200,000 | [2]
[1] | The majority of these results are for the second quarter of each respective year.
[2] | The majority of these results are for the nine months ended June 30 of each respective year.

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