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Investments (Aggregated Balance Sheet Summarized Financial Information for Partnerhips in our Alternative Investment Portfolio) (Details) - Investments Accounted For Under The Equity Method [Member] - USD ($) $ in Millions | Sep. 30, 2015 | Sep. 30, 2014
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Investments | $ 7,527 | $ 10,096
Total assets | 8,515 | 10,695
Total liabilities | 316 | 545
Partners' capital | $ 8,199 | $ 10,150

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