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Investments (Aggregated Income Statement Summarized Financial Information for Partnerhips in our Alternative Investment Portfolio) (Details) (USD $) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Sep. 30, 2013 Investments Accounted For Under The Equity Method [Member] | Sep. 30, 2012 Investments Accounted For Under The Equity Method [Member] | Sep. 30, 2011 Investments Accounted For Under The Equity Method [Member] | Dec. 31, 2013 Partnership Interest [Member] | Dec. 31, 2012 Partnership Interest [Member] | Dec. 31, 2011 Partnership Interest [Member]
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Investment Income |  |  |  |  |  |  |  |  |  |  |  | $ 406,000,000 | $ 226,000,000 | $ 564,000,000 |  |  |
Realized gains |  |  |  |  |  |  |  |  |  |  |  | 913,000,000 | 1,015,000,000 | 893,000,000 |  |  |
Net change in unrealized appreciation (depreciation) |  |  |  |  |  |  |  |  |  |  |  | 382,000,000 | (100,000,000) | 1,485,000,000 |  |  |
Net Income |  |  |  |  |  |  |  |  |  |  |  | 1,701,000,000 | 1,141,000,000 | 2,942,000,000 |  |  |
Net investment income earned | $ 35,313,000 | $ 32,457,000 | $ 34,003,000 | $ 32,870,000 | $ 34,593,000 | $ 30,650,000 | $ 34,006,000 | $ 32,628,000 | $ 134,643,000 | $ 131,877,000 | $ 147,443,000 |  |  |  | $ 15,000,000 | $ 9,000,000 | $ 21,000,000

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