Goodwill and Other Intangibles - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 92	$ 76
Accumulated amortization	(18)	(9)
Net carrying amount	74	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	(8)	(4)
Net carrying amount	29	28
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	22	14
Accumulated amortization	(5)	(3)
Net carrying amount	17	11
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	3	1
Accumulated amortization	(1)	0
Net carrying amount	$ 2	$ 1