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Basis of Presentation - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Accounting Policies [Abstract]
Reclassification of debt balance to leases	$ 229

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- Definition

Prior period reclassification from debt balance to leases.

+ References

No definition available.

+ Details

Name:	nov_PriorPeriodReclassificationFromDebtBalanceToLeases
Namespace Prefix:	nov_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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- References

No definition available.

+ Details

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