General Information	9 Months Ended
Sep. 30, 2021
Accounting Policies [Abstract]
General Information	1. General Information The unaudited condensed consolidated financial statements of Diamond Offshore Drilling, Inc. and subsidiaries, which we refer to as “Diamond Offshore,” “we,” “us” or “our,” should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2020, as amended by Amendment No. 1 on Form 10-K/A (File No. 1-13926). To facilitate our financial statement presentations, we refer to the post-emergence reorganized company in these unaudited condensed consolidated financial statements and footnotes as the “Successor” for periods subsequent to April 23, 2021 and to the pre-emergence company as the “Predecessor” for periods on or prior to April 23, 2021. This delineation between Predecessor periods and Successor periods is shown in the unaudited condensed consolidated financial statements, certain tables within the footnotes to the unaudited condensed consolidated financial statements and other parts of this Quarterly Report on Form 10-Q through the use of a black line, calling out the lack of comparability between periods. Interim Financial Information The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (or GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission. Accordingly, pursuant to such rules and regulations, they do not include all disclosures required by GAAP for annual financial statements. The condensed consolidated financial information has not been audited but, in the opinion of management, includes all adjustments (consisting of normal recurring adjustments) necessary for a fair presentation of Diamond Offshore’s condensed consolidated balance sheets, statements of operations, statements of comprehensive loss, statements of stockholders’ equity and statements of cash flows at the dates and for the periods indicated. Results of operations for interim periods are not necessarily indicative of results of operations for the respective full years. Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amount of revenues and expenses during the reporting period. Actual results could differ from those estimated. Restricted Cash We maintain restricted cash bank accounts, of which $24.2 million is subject to restrictions pursuant to a management and marketing services agreement with an offshore drilling company and $0.1 million is subject to restrictions pursuant to a court order, to settle certain professional fees incurred upon or prior to our emergence from bankruptcy. See Note 2 “Chapter 11 Proceedings.” We classify such restricted cash accounts in current assets if the restrictions are expected to expire or otherwise be resolved within one year or if such funds are considered to offset current liabilities. At September 30, 2021, our restricted cash was considered to be current and was recorded in “Restricted cash” in our unaudited Condensed Consolidated Balance Sheets. Change in Accounting Policies Concurrent with emergence from bankruptcy, the Successor adopted a new policy for the deferral and amortization of the costs of planned periodic inspections of its drilling rigs (or vessels) that are typically incurred on five-year or two-and-one-half year intervals, to ensure compliance with applicable regulations and maintain certifications for vessels with classification societies. These costs include mobilization of the vessel into the shipyard, drydocking, support services while in shipyard and the associated survey or inspection costs necessary to maintain class certifications. These recertification costs are typically incurred while the vessel is in drydock and may be performed concurrent with other vessel maintenance and improvement activities. Costs related to the recertification of vessels are deferred and amortized over the survey interval on a straight-line basis. Maintenance costs incurred at the time of the recertification drydocking, which are not related to the recertification of the vessel are expensed as incurred. Costs for vessel improvements which either extend the vessel’s useful life or increase the vessels functionality are capitalized and depreciated. The company’s previous policy (Predecessor) was to expense vessel recertification costs in the period incurred.

General Information

9 Months Ended

Sep. 30, 2021

1. General Information

The unaudited condensed consolidated financial statements of Diamond Offshore Drilling, Inc. and subsidiaries, which we refer to as “Diamond Offshore,” “we,” “us” or “our,” should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2020, as amended by Amendment No. 1 on Form 10-K/A (File No. 1-13926). To facilitate our financial statement presentations, we refer to the post-emergence reorganized company in these unaudited condensed consolidated financial statements and footnotes as the “Successor” for periods subsequent to April 23, 2021 and to the pre-emergence company as the “Predecessor” for periods on or prior to April 23, 2021. This delineation between Predecessor periods and Successor periods is shown in the unaudited condensed consolidated financial statements, certain tables within the footnotes to the unaudited condensed consolidated financial statements and other parts of this Quarterly Report on Form 10-Q through the use of a black line, calling out the lack of comparability between periods.

Interim Financial Information

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (or GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission. Accordingly, pursuant to such rules and regulations, they do not include all disclosures required by GAAP for annual financial statements. The condensed consolidated financial information has not been audited but, in the opinion of management, includes all adjustments (consisting of normal recurring adjustments) necessary for a fair presentation of Diamond Offshore’s condensed consolidated balance sheets, statements of operations, statements of comprehensive loss, statements of stockholders’ equity and statements of cash flows at the dates and for the periods indicated. Results of operations for interim periods are not necessarily indicative of results of operations for the respective full years.

Use of Estimates in the Preparation of Financial Statements

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amount of revenues and expenses during the reporting period. Actual results could differ from those estimated.

Restricted Cash

We maintain restricted cash bank accounts, of which $24.2 million is subject to restrictions pursuant to a management and marketing services agreement with an offshore drilling company and $0.1 million is subject to restrictions pursuant to a court order, to settle certain professional fees incurred upon or prior to our emergence from bankruptcy. See Note 2 “Chapter 11 Proceedings.”

We classify such restricted cash accounts in current assets if the restrictions are expected to expire or otherwise be resolved within one year or if such funds are considered to offset current liabilities. At September 30, 2021, our restricted cash was considered to be current and was recorded in “Restricted cash” in our unaudited Condensed Consolidated Balance Sheets.

Change in Accounting Policies

Concurrent with emergence from bankruptcy, the Successor adopted a new policy for the deferral and amortization of the costs of planned periodic inspections of its drilling rigs (or vessels) that are typically incurred on five-year or two-and-one-half year intervals, to ensure compliance with applicable regulations and maintain certifications for vessels with classification societies. These costs include mobilization of the vessel into the shipyard, drydocking, support services while in shipyard and the associated survey or inspection costs necessary to maintain class certifications. These recertification costs are typically incurred while the vessel is in drydock and may

be performed concurrent with other vessel maintenance and improvement activities. Costs related to the recertification of vessels are deferred and amortized over the survey interval on a straight-line basis. Maintenance costs incurred at the time of the recertification drydocking, which are not related to the recertification of the vessel are expensed as incurred. Costs for vessel improvements which either extend the vessel’s useful life or increase the vessels functionality are capitalized and depreciated. The company’s previous policy (Predecessor) was to expense vessel recertification costs in the period incurred.