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Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020
Leases [Abstract]
Impairment of right-of-use assets	$ 42	$ 42

X

- Definition

Impairment of right-of-use assets.

+ References

No definition available.

+ Details

Name:	nov_ImpairmentOfRightOfUseAssets
Namespace Prefix:	nov_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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- References

No definition available.

+ Details

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