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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, 2017 | Sep. 30, 2016
--- | --- | ---
Investments | $ 21,046 | $ 11,244
Total assets | 22,357 | 12,075
Total liabilities | 4,767 | 1,802
Partners' capital | $ 17,590 | $ 10,273

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