Income Taxes - Schedule of Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Current
Federal					$ (2)	$ 47	$ 99
State					6	8	24
Non-U.S.					17	14	12
Current income tax expense					21	69	135
Deferred
Federal					136	106	14
State					9	12	2
Non-U.S.					0	(1)	(3)
Deferred income tax expense					145	117	13
Income tax expense	$ 2	$ 3	$ 2	$ 71	$ 166	$ 186	$ 148