Debt - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Debt Instrument [Line Items]
Repayments senior notes	$ 3,000	$ 0
Senior Notes \| December 14, 2020 Senior Note
Debt Instrument [Line Items]
Repayments senior notes	$ 3,000

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

Name:	us-gaap_RepaymentsOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration