Revenue - Contract Balances (Details) - USD ($)	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2019
Change In Contract With Customer, Assets [Roll Forward]
Contract assets - Beginning balance, October 1, 2018	$ 0	$ 10,140,000
Additional revenue recognized over-time		32,348,000
Less amounts billed to the customers		(33,727,000)
Contract assets - Ending balance, March 31, 2019	8,761,000	8,761,000
Change In Contract With Customer, Liability [Roll Forward]
Contract liabilities (included within Accrued liabilities) - Beginning balance, October 1, 2018	0
Payments received in advance of performance obligations	(1,000,000)
Performance obligations satisfied	1,000,000
Contract liabilities (included within Accrued liabilities) - Ending balance, March 31, 2019	0	$ 0
Impairment loss on contract assets	$ 0