Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2018
Statement Of Cash Flows [Abstract]
Cash acquired in acquisition of business	$ 1	$ 1

The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585

Name:	us-gaap_CashAcquiredFromAcquisition
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration