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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, 2018	Sep. 30, 2017
Investments	$ 28,292	$ 21,046
Total assets	30,377	22,357
Total liabilities	4,532	4,767
Partners' capital	$ 25,845	$ 17,590

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