Commitment and Contingencies - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Accrued workers' compensation insurance	$ 6,519	$ 5,529

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable within one year (or the operating cycle, if longer). Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 25
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6409733&loc=d3e19512-108361

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20028-108363

Name:	us-gaap_DeferredCompensationLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant