Redeemable non-controlling interest - Additional Information (Details) - Asia Offshore Drilling Ltd - USD ($)	Apr. 04, 2018	Dec. 31, 2019
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling interest, ownership percentage by parent		66.24%
Mermaid
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners		33.76%
Noncontrolling interest owners option to redeem, price ceiling	$ 125,000,000
Noncontrolling interest parent option to redeem, price floor	75,000,000
Purchase price threshold (less than) for cash settlement	50,000,000
Purchase price threshold (greater than) for settlement in shares	50,000,000
Purchase price, amount to be redeemed in cash if price is above threshold	$ 50,000,000

Noncontrolling Interest, Noncontrolling Owners Option To Redeem, Repurchase Price Ceiling

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- Definition

Noncontrolling Interest, Parent Option To Redeem, Repurchase Price Floor

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- Definition

Noncontrolling Interest, Redemption, Amount Required To Be Redeemed In Cash If Redemption Price Is Above Threshold

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No definition available.

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- Definition

Noncontrolling Interest, Redemption Price Threshold For Cash Settlement, Less Than

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No definition available.

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- Definition

Noncontrolling Interest, Redemption Price Threshold For Settlement In Shares, Greater Than

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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No definition available.

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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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.

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No definition available.

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