Goodwill and Other Intangible Assets - Other Intangible Assets Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 94	$ 126	$ 188	$ 275
Future amortization expense, 2018	383		383
Future amortization expense, 2019	379		379
Future amortization expense, 2020	371		371
Future amortization expense, 2021	361		361
Future amortization expense, 2022	$ 348		$ 348