Acquisitions and Divestitures - Narrative (Details) $ in Millions					1 Months Ended	12 Months Ended
	Jul. 13, 2018 USD ($) company-owned_and_franchised_locations franchise_service_center_stores	Oct. 02, 2017 USD ($) franchise	Jan. 31, 2017 USD ($) service_center_store	Feb. 01, 2016 USD ($) service_center_store franchise_service_center_stores	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($) service_center_store franchise_service_center_stores	Sep. 30, 2017 USD ($) service_center_store franchise_service_center_stores	Sep. 30, 2016 USD ($) service_center_store franchise_service_center_stores	Nov. 30, 2017
Business Acquisition [Line Items]
Number of service center stores | service_center_store						136	43	104
Purchase price						$ 125	$ 72	$ 79
Number of franchise service center stores acquired | franchise_service_center_stores						73	14	42
Number of former franchise service center stores acquired | franchise_service_center_stores						60		9
Number of service center stores acquired in single and multi-store transactions | service_center_store						3	29	53
Payments for business acquisition								$ 4
Goodwill						$ 381	$ 330	264
Quick Lubes
Business Acquisition [Line Items]
Number of service center stores | service_center_store						7	15
Goodwill						$ 252	$ 201	$ 135
Quick Lubes | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Number of service center stores sold to franchisee | service_center_store						2
Gain on sale						$ 2
THAILAND
Business Acquisition [Line Items]
Equity method ownership percentage									70.00%
Additional ownership percentage of joint venture, purchased					30.00%
Consideration paid to acquire additional interest in subsidiary					$ 16
Customer relationships
Business Acquisition [Line Items]
Weighted average useful life						13 years
Henley Bluewater, LLC
Business Acquisition [Line Items]
Purchase price		$ 60
Number of former franchise service center stores acquired | franchise		56
Goodwill		$ 36
Weighted average useful life						7 years
Great Canadian Oil Change
Business Acquisition [Line Items]
Purchase price	$ 53
Number of franchise service center stores acquired | franchise_service_center_stores	73
Goodwill	$ 16
Number of company-owned and franchised locations in North America | company-owned_and_franchised_locations	1,200
Great Canadian Oil Change | Trade Names
Business Acquisition [Line Items]
Weighted average useful life						20 years
Increase in intangible assets as a result of adjustment	$ 27
Great Canadian Oil Change | Customer relationships
Business Acquisition [Line Items]
Weighted average useful life						15 years
Increase in intangible assets as a result of adjustment	$ 9
Time-It Lube
Business Acquisition [Line Items]
Number of service center stores | service_center_store			28
Purchase price			$ 49
Goodwill			$ 45
Oil Can Henry's International, Inc.
Business Acquisition [Line Items]
Number of service center stores | service_center_store				47
Purchase price				$ 62
Number of franchise service center stores acquired | franchise_service_center_stores				42
Goodwill				$ 82
Assumption of debt in business acquisition				$ 11