Goodwill and Other Intangibles - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 91	$ 76
Accumulated amortization	(16)	(9)
Net carrying amount	75	67
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	30	29
Accumulated amortization	(4)	(2)
Net carrying amount	26	27
Reacquired franchise rights
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	37	32
Accumulated amortization	(7)	(4)
Net carrying amount	30	28
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	21	14
Accumulated amortization	(4)	(3)
Net carrying amount	17	11
Other
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	3	1
Accumulated amortization	(1)	0
Net carrying amount	$ 2	$ 1