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Tax - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reconciliation Of Statutory Federal Tax Rate [Line Items]
Effective tax rate	37.60%us-gaap_EffectiveIncomeTaxRateContinuingOperations	30.40%us-gaap_EffectiveIncomeTaxRateContinuingOperations
Effective tax rate excluding discrete items	28.90%us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes
U.S. federal statutory rate	35.00%us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Unrecognized tax benefit	$ 185us-gaap_UnrecognizedTaxBenefits
Increase in uncertain tax position identified in foreign jurisdiction	69us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromSettlementsWithTaxingAuthorities
Realized [Member]
Reconciliation Of Statutory Federal Tax Rate [Line Items]
Unrecognized tax benefit	$ 112us-gaap_UnrecognizedTaxBenefits / us-gaap_TaxCreditCarryforwardAxis = nov_RealizedMember

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 12

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-Topic 235

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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Amount of increase in unrecognized tax benefits resulting from settlements with taxing authorities.

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