Income Taxes - Schedule of Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Current
Federal	$ 47	$ 99	$ 81
State	8	24	16
Foreign	14	12	13
Current income tax expense	69	135	110
Deferred
Federal	106	14	(5)
State	12	2	(1)
Foreign	(1)	(3)	(3)
Deferred income tax expense	117	13	(9)
Income tax expense	186	$ 148	$ 101
Release of the valuation allowance	4
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss generated during period	96
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss generated during period	$ 10