Risk management and financial instruments - Sensitivity Analysis (Details) $ in Millions	Jun. 30, 2019 USD ($)
Derivative [Line Items]
Amount	$ 5,296
Impact of 1% point increase in rates (after impact of interest rate cap)	27
Floating rate debt obligations
Derivative [Line Items]
Impact of 1% point increase in rates (after impact of interest rate cap)	42
Floating rate debt obligations \| Senior Credit Facilities
Derivative [Line Items]
Amount	5,662
Impact of 1% point increase in rates (before impact of interest rate cap)	57
Less: impact of LIBOR CAP	(21)
Impact of 1% point increase in rates (after impact of interest rate cap)	36
Floating rate debt obligations \| Senior Credit Facilities \| Hedged
Derivative [Line Items]
Amount	4,500
Impact of 1% point increase in rates (before impact of interest rate cap)	45
Less: impact of LIBOR CAP	(21)
Impact of 1% point increase in rates (after impact of interest rate cap)	24
Floating rate debt obligations \| Senior Credit Facilities \| Not hedged
Derivative [Line Items]
Amount	1,162
Impact of 1% point increase in rates (before impact of interest rate cap)	12
Less: impact of LIBOR CAP	0
Impact of 1% point increase in rates (after impact of interest rate cap)	$ 12

Sensitivity Analysis For Interest Rate Risk, Impact Of LIBOR CAP

No definition available.

Name:	sdrl_SensitivityAnalysisForInterestRateRiskImpactOfLIBORCAP
Namespace Prefix:	sdrl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sensitivity Analysis For Interest Rate Risk, Reasonably Possible Change In Risk Variable Before Impact Of Interest Rate Cap, Debt

+ References

No definition available.

+ Details

Name:	sdrl_SensitivityAnalysisForInterestRateRiskReasonablyPossibleChangeInRiskVariableBeforeImpactOfInterestRateCapDebt
Namespace Prefix:	sdrl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sensitivity Analysis For Interest Rate Risk, Reasonably Possible Change In Risk Variable, Debt

+ References

No definition available.

+ Details

Name:	sdrl_SensitivityAnalysisForInterestRateRiskReasonablyPossibleChangeInRiskVariableDebt
Namespace Prefix:	sdrl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAmountOfHedgedItem
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- 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

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=sdrl_FloatingRateDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=sdrl_SeniorCreditFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: