Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Transfers in or out Level 3, Assets	$ 0	$ 0

Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

No definition available.

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