Income Taxes Uncertain Tax Position, Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]
Income Tax Examination, estimate of impact		$ 100
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities		(440)
Unrecognized Tax Benefits, Decrease (Increase) Resulting from Tax Audit Resolution	$ 99	0	$ (123)	$ 0
Unrecognized Tax Benefits	1,159	1,836	1,159	1,607	$ 1,302
Amount of unrecognized tax benefits which may impact effective tax rate	1,104	1,734	1,104	1,457
Total net accrued interest, net of tax benefit	$ 41	$ 67	$ 41	$ 106