Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended
Dec. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Increase (decrease) in environmental liability	$ 3
Estimated undiscounted liabilities payment period	30 years

Increase (decrease) in the accrual for environmental loss contingencies during the reporting period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q2)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration