Revenue Recognition and Related Costs - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Amortization period for incremental costs	1 year
Costs and estimated earnings in excess of billings	$ 4,709,000	$ 6,405,000
Accounts receivable related to contracts with customers	346,000	223,000
Current Liabilities [Member]
Disaggregation of Revenue [Line Items]
Customer deposits related to contracts with customers	$ 2,697,000	$ 3,853,000
Maximum [Member]
Disaggregation of Revenue [Line Items]
Contract assets collection period	1 year