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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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