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Investment in Debt Security - Additional Information (Details) - International Seismic Marine - Debt Security - Third in Line lien on Assets - USD ($) $ in Millions | 12 Months Ended |
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Sep. 30, 2020 | Jul. 13, 2020
Schedule Of Available For Sale Securities [Line Items] |  |
Face value of debt security |  | $ 13.0
Unpaid invoices and later fees owed by customer |  | $ 13.0
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

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