Revenue - Contract Balances (Details)	9 Months Ended
	Jun. 30, 2020 USD ($)
Change In Contract With Customer, Assets [Roll Forward]
Contract assets - Beginning balance, October 1, 2019	$ 10,349,000
Additional revenue recognized over-time	51,132,000
Less amounts billed to the customers	(48,347,000)
Contract assets - Ending balance, June 30, 2020	13,134,000
Change In Contract With Customer, Liability [Roll Forward]
Contract liabilities (included within Accrued liabilities) - Beginning balance, October 1, 2019	(382,000)
Payments received in advance of performance obligations	0
Performance obligations satisfied	382,000
Contract liabilities (included within Accrued liabilities) - Ending balance, June 30, 2020	0
Impairment loss on contract assets	$ 0