Revenue Recognition and Related Costs - Additional Information (Detail) - USD ($)	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Amortization period for incremental costs	1 year
Costs and estimated earnings in excess of billings	$ 0	$ 6,405,000
Accounts receivable related to contracts with customers	268,000	223,000
Billings in excess of costs and estimated earnings	685,000	0
Current Liabilities [Member]
Disaggregation of Revenue [Line Items]
Customer deposits related to contracts with customers	3,761,000	3,853,000
Billings in excess of costs and estimated earnings	$ 685,000	$ 0