Costs and Estimated Earnings in Excess of Billings - Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts (Detail) - USD ($)	Mar. 31, 2018	Sep. 30, 2017
Costs in Excess of Billings on Uncompleted Contracts or Programs [Abstract]
Costs incurred on uncompleted contracts	$ 15,741,000	$ 10,250,000
Estimated earnings	5,999,000	3,161,000
Costs and estimated earnings on uncompleted contracts	21,740,000	13,411,000
Costs and estimated earnings on uncompleted contracts	21,740,000	13,411,000
Billings to date	10,812,000	6,643,000
Costs and estimated earnings in excess of billings	$ 10,928,000	$ 6,768,000