Costs and Estimated Earnings in Excess of Billings and Billings in Excess of Costs and Estimated Earnings - Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts (Detail) - USD ($)	Jun. 30, 2021	Sep. 30, 2020
Costs in Excess of Billings on Uncompleted Contracts or Programs [Abstract]
Costs incurred on uncompleted contracts	$ 7,975,000	$ 10,390,000
Estimated earnings	3,368,000	4,680,000
Costs and estimated earnings on uncompleted contracts	11,343,000	15,070,000
Billings to date	12,028,000	8,665,000
Costs and estimated earnings in excess of billings	0	6,405,000
Billings in excess of costs and estimated earnings	$ 685,000	$ 0