Investment in Debt Security - Additional Information (Details) - International Seismic Marine - Debt Security - Third in Line lien on Assets - USD ($) $ in Millions	12 Months Ended
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

Identification of the lender and information about a contractual promise to repay a short-term or long-term obligation, which includes borrowings under lines of credit, notes payable, commercial paper, bonds payable, debentures, and other contractual obligations for payment. This may include rationale for entering into the arrangement, significant terms of the arrangement, which may include amount, repayment terms, priority, collateral required, debt covenants, borrowing capacity, call features, participation rights, conversion provisions, sinking-fund requirements, voting rights, basis for conversion if convertible and remarketing provisions. The description may be provided for individual debt instruments, rational groupings of debt instruments, or by debt in total.

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