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Marketable securities (Tables) | 12 Months Ended
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Dec. 31, 2020
Marketable Securities [Abstract] |
Marketable Securities Held | The below table shows the carrying value of our investments in marketable securities for periods presented in this report.
(In $ millions) |  | December 31, 2020 |  | December 31, 2019
Seadrill Partners- Common units |  | — |  |  | 2 |
Archer |  | 8 |  |  | 9 |
Total marketable securities |  | 8 |  |  | 11 |
Gross Realized Gains and Losses Related to Marketable Securities | The below table shows the gain and losses recognized through net income for the periods presented in this report.
|  | Successor |  | Predecessor
(In $ millions) |  | Year ended December 31, 2020 |  | Year ended December 31, 2019 |  | Period from July 2, 2018 through December 31, 2018 |  |  | Period from January 1, 2018 through July 1, 2018
Seadrill Partners - Common Units - unrealized loss on marketable securities |  | (2) |  |  | (43) |  |  | (45) |  |  |  | (5) |
Archer - unrealized (loss)/gain on marketable securities |  | (1) |  |  | (3) |  |  | (19) |  |  |  | 2 |
Total unrealized loss on marketable securities |  | (3) |  |  | (46) |  |  | (64) |  |  |  | (3) |

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- Definition Tabular disclosure of changes of carrying value of marketable securities during the period. + References No definition available. + Details
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- Definition Tabular disclosure of marketable securities. This may consist of investments in certain debt and equity securities, short-term investments and other assets. + References No definition available. + Details
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