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Costs and Estimated Earnings in Excess of Billings - Costs and Estimated Earnings in Excess of Billings on Uncompleted Contracts (Detail) - USD ($) | Sep. 30, 2020 | Sep. 30, 2019
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Costs in Excess of Billings on Uncompleted Contracts or Programs [Abstract] |  |
Costs incurred on uncompleted contracts | $ 10,390,000 | $ 18,707,000
Estimated earnings | 4,680,000 | 9,063,000
Costs and estimated earnings on uncompleted contracts | 15,070,000 | 27,770,000
Billings to date | 8,665,000 | 13,932,000
Costs and estimated earnings in excess of billings | $ 6,405,000 | $ 13,838,000

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