Income Taxes Significant Components of Company's Income Tax Provision from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Tax expense at federal statutory rate		$ 895	$ 371	$ 326
State income taxes, net of federal benefit		23	(6)	(6)
Foreign income tax expense at different rates and foreign losses without tax benefits		(309)	(122)	(175)
U.S. tax on foreign income		(407)	(194)	39
Reserve and valuation allowance adjustments		(164)	0	(99)
U.S. credits and incentives		(3)	(14)	(7)
Effective Income Tax Rate Reconciliation, Acquisitions and Dispositions of Business, Amount		571	163	0
Restructuring and impairment costs		65	28	0
Other	$ 53	34	(29)	(7)
Income tax provision		$ 705	$ 197	$ 71