Supporting Financial Information - Accounts Payable, Accrued Expense and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts payable	$ 15,990	$ 14,645
Accrued benefits	2,711	2,833
Accrued bonus and incentive compensation	1,786	2,340
Accrued workers' compensation insurance	6,519	5,529
Other accrued expenses	5,624	3,231
Accounts payable, accrued expenses, and other current liabilities	$ 32,630	$ 28,578