Costs and Estimated Earnings in Excess of Billings - Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts (Detail) - USD ($)	Jun. 30, 2020	Sep. 30, 2019
Costs in Excess of Billings on Uncompleted Contracts or Programs [Abstract]
Costs incurred on uncompleted contracts	$ 13,792,000	$ 18,707,000
Estimated earnings	5,555,000	9,063,000
Costs and estimated earnings on uncompleted contracts	19,347,000	27,770,000
Billings to date	9,283,000	13,932,000
Costs and estimated earnings in excess of billings	$ 10,064,000	$ 13,838,000