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Investment in associated companies - Ownership Percentage (Details)	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2019	Dec. 31, 2018	Jul. 01, 2018
Seabras Sapura
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%
Seabras Sapura | Joint Venture Partner
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
SeaMex
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%		50.00%	50.00%
SeaMex | Joint Venture Partner
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Sonadrill
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%		0.00%	0.00%
Sonadrill | Joint Venture Partner
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Gulfdrill
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%	0.00%	0.00%
Gulfdrill | Joint Venture Partner
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%

X

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ 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.

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