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Fair Value Measurements Investments Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investment Gains (Losses)
Securities classified as trading and measured at fair value	$ 2,100		$ 2,100
NDT unfunded commitments related to private partnerships	92		92
SERP
Investment Gains (Losses)
Unrealized gains (losses) on investments	0	$ 1	0	$ 2
LTDCP [Member]
Investment Gains (Losses)
Unrealized gains (losses) on investments	0	0	(1)	0
NDT
Investment Gains (Losses)
Unrealized gains (losses) on investments	(19)	36	15	72
ART
Investment Gains (Losses)
Unrealized gains (losses) on investments	(3)	$ 9	12	$ 27
Maximum
Investment Gains (Losses)
Equity investments not required to be measured at fair value	$ 1		$ 1