Costs and Estimated Earnings in Excess of Billings - Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts (Detail) - USD ($)	Sep. 30, 2021	Sep. 30, 2020
Costs in Excess of Billings on Uncompleted Contracts or Programs [Abstract]
Costs incurred on uncompleted contracts	$ 11,483,000	$ 10,390,000
Estimated earnings	4,395,000	4,680,000
Costs and estimated earnings on uncompleted contracts	15,878,000	15,070,000
Billings to date	13,975,000	8,665,000
Costs and estimated earnings in excess of billings	$ 1,903,000	$ 6,405,000