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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

X
- References No definition available. + Details
Name: | us-gaap_LeasesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration