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Marketable securities - Gross Realized Gains and Losses Related to Marketable Securities (Details) - USD ($) $ in Millions | 6 Months Ended
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Jun. 30, 2021 | Jun. 30, 2020
Gain (Loss) on Securities [Line Items] |  |
Total unrealized gain / (loss) on marketable securities | $ 5 | $ (6)
Seadrill Partners - Common units - unrealized loss on marketable securities |  |
Gain (Loss) on Securities [Line Items] |  |
Total unrealized gain / (loss) on marketable securities | 0 | (2)
Archer - unrealized gain / (loss) on marketable securities |  |
Gain (Loss) on Securities [Line Items] |  |
Total unrealized gain / (loss) on marketable securities | $ 5 | $ (4)

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- Definition Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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- Details
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