Goodwill and Other Intangibles - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 76	$ 8
Accumulated amortization	(9)	(3)
Net carrying amount	67	5
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	29	2
Accumulated amortization	(2)	(1)
Net carrying amount	27	1
Reacquired franchise rights
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	32	0
Accumulated amortization	(4)	0
Net carrying amount	28	0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	14	5
Accumulated amortization	(3)	(2)
Net carrying amount	11	3
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1	1
Accumulated amortization	0	0
Net carrying amount	$ 1	$ 1