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Investments - Additional Information (Details) - USD ($) | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2021 | Jan. 31, 2021 | Jun. 30, 2021 | Mar. 31, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020 | Sep. 30, 2020 | Jul. 13, 2020
Schedule Of Available For Sale Securities [Line Items] |  |  |  |  |  |  |  |  |
Realized gains (losses) |  |  | $ (1,000) |  | $ 0 | $ (1,000) | $ 0 |  |
Short-term investments |  |  |  |  |  |  |  | $ 0 |
Proceeds from sale of investment in debt security |  |  |  |  |  | 2,069,000 |  |  |
Gain on investments, net |  |  | 1,727,000 |  |  | $ 1,996,000 |  |  |
Debt Security |  |  |  |  |  |  |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |  |  |  |  |  |  |
Proceeds from sale of investment in debt security | $ 1,800,000 | $ 300,000 |  |  |  |  |  |  |
Additional cash compensation to be received based on conditions met |  | 2,400,000 |  |  |  |  |  |  |
Repurchase price of bond if conditions not met |  | $ 1.00 |  |  |  |  |  |  |
Gain on investments, net |  |  | 1,700,000 | $ 300,000 |  |  |  |  |
Reduction of additional cash compensation required from buyer to obtain rights to bond |  |  | $ 1,800,000 |  |  |  |  |  |
Debt Security | Third in Line lien on Assets | International Seismic Marine |  |  |  |  |  |  |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |  |  |  |  |  |  |
Estimated Fair Value |  |  |  |  |  |  |  |  | $ 13,000,000.0
Unpaid invoices and later fees owed by customer |  |  |  |  |  |  |  |  | $ 13,000,000.0
Debt instrument, description |  |  |  |  |  | The bond is secured by a third in line lien on the assets owned by the customer and has an 8% interest rate with bi-annual interest and possible principal payments based on available excess cash flows. Interest payments can be made either in cash or in-kind payments in the form of additional debt security. In-kind interest payments require an 8.8% interest rate. |  |  |
Investment interest rate |  |  |  |  |  |  |  |  | 8.00%
In-kind payments, interest rate |  |  |  |  |  |  |  |  | 8.80%
Maturity date |  |  |  |  |  |  |  |  | Jul. 13, 2022
Minimum |  |  |  |  |  |  |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |  |  |  |  |  |  |
Short-term investments maturity date | Sep. 30, 2021 |  | Sep. 30, 2021 |  |  | Sep. 30, 2021 |  |  |
Maximum |  |  |  |  |  |  |  |  |
Schedule Of Available For Sale Securities [Line Items] |  |  |  |  |  |  |  |  |
Short-term investments maturity date | Sep. 30, 2022 |  | Sep. 30, 2022 |  |  | Sep. 30, 2022 |  |  |

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