Intangible Assets and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2017	Mar. 31, 2016	Feb. 28, 2017	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired		$ 302	$ 14
Finite-lived Intangible Assets Acquired	$ 104
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	8 years
Goodwill (Note 2 and Note 5)	$ 14,825	$ 14,825		$ 181	$ 15,066