Revenue Recognition and Related Costs - Additional Information (Detail) - USD ($)	9 Months Ended
	Jun. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Amortization period for incremental costs	1 year
Costs and estimated earnings in excess of billings	$ 10,064,000	$ 13,838,000
Accounts receivable related to contracts with customers	281,000	301,000
Current Liabilities [Member]
Disaggregation of Revenue [Line Items]
Customer deposits related to contracts with customers	$ 2,651,000	$ 1,918,000
Maximum [Member]
Disaggregation of Revenue [Line Items]
Contract assets collection period	1 year