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Basis of Presentation - Additional Information (Detail) | 9 Months Ended
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Sep. 30, 2018
Accounting Policies [Abstract] |
Maturity period of investments description | Three months or less

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- Definition Maturity period to qualify as cash equivalent maximum. + References No definition available. + Details
Name: | nov_MaturityPeriodToQualifyAsCashEquivalentMaximum
Namespace Prefix: | nov_
Data Type: | xbrli:stringItemType
Balance Type: | na
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