Revenue - Contract Balances (Details) - USD ($)	9 Months Ended	12 Months Ended
	Jun. 30, 2021	Sep. 30, 2020
Change In Contract With Customer, Assets [Roll Forward]
Contract assets - Beginning balance	$ 11,997,000
Additional revenue recognized over-time	49,070,000
Less amounts billed to the customers	(46,401,000)
Contract assets - Ending balance	14,666,000	$ 11,997,000
Change In Contract With Customer, Liability [Roll Forward]
Contract liabilities (included within Accrued liabilities) - Beginning balance	(636,000)
Payments received in advance of performance obligations	(628,000)
Performance obligations satisfied	763,000
Contract liabilities (included within Accrued liabilities) - Ending balance	(501,000)	(636,000)
Impairment loss on contract assets	$ 0	$ 0