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v3.20.4

Non-controlling interest - Additional Information (Details) - USD ($) | 1 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Aug. 31, 2020 | Feb. 29, 2020 | Dec. 31, 2020 | Sep. 11, 2020 | Sep. 10, 2020 | Jul. 31, 2020 | Jul. 01, 2018
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Payment for option to purchase non-controlling interest |  | $ 11,000,000 |  |  |  |  |
Option to purchase non-controlling interest, purchase price |  | $ 1 |  |  |  |  |
Seadrill Nigeria Operations Limited | West Jupiter Drillship |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Ownership percentage |  |  | 10.00% |  |  |  |
North Atlantic Drilling Ltd |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Noncontrolling interest, ownership percentage by parent |  |  |  |  |  |  | 70.36%
Sevan Drilling Limited |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Noncontrolling interest, ownership percentage by parent |  |  |  |  |  |  | 50.11%
Asia Offshore Drilling Ltd |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Noncontrolling interest, ownership percentage by parent |  |  |  | 100.00% | 66.24% | 66.24% |
Asia Offshore Drilling Ltd | Mermaid |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Noncontrolling interest, percentage sold | 34.00% |  |  |  |  |  |
Noncontrolling interest, value sold | $ 31,000,000 |  |  |  |  |  |

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