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Investments (Aggregated Balance Sheet Summarized Financial Information for Partnerships in our Alternative Investment Portfolio) (Details) - Investments Accounted For Under The Equity Method [Member] - USD ($) $ in Millions | Sep. 30, 2016 | Sep. 30, 2015
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Investments | $ 11,244 | $ 7,527
Total assets | 12,075 | 8,515
Total liabilities | 1,802 | 316
Partners' capital | $ 10,273 | $ 8,199

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