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Summary of Significant Accounting Policies - Goodwill is Identified by Segment (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 9,049us-gaap_Goodwill	$ 7,172us-gaap_Goodwill
Goodwill acquired during period	167us-gaap_GoodwillAcquiredDuringPeriod	1,903us-gaap_GoodwillAcquiredDuringPeriod	1,000us-gaap_GoodwillAcquiredDuringPeriod
Goodwill disposed of during the period	(403)us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwill1
Currency translation adjustments and other	(274)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments	(26)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments
Goodwill, Ending Balance	8,539us-gaap_Goodwill	9,049us-gaap_Goodwill	7,172us-gaap_Goodwill
Discontinued Operations [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	333us-gaap_Goodwill / us-gaap_StatementOperatingActivitiesSegmentAxis = us-gaap_SegmentDiscontinuedOperationsMember	343us-gaap_Goodwill / us-gaap_StatementOperatingActivitiesSegmentAxis = us-gaap_SegmentDiscontinuedOperationsMember
Goodwill disposed of during the period	(332)us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwill1 / us-gaap_StatementOperatingActivitiesSegmentAxis = us-gaap_SegmentDiscontinuedOperationsMember
Currency translation adjustments and other	(1)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementOperatingActivitiesSegmentAxis = us-gaap_SegmentDiscontinuedOperationsMember	(10)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementOperatingActivitiesSegmentAxis = us-gaap_SegmentDiscontinuedOperationsMember
Goodwill, Ending Balance		333us-gaap_Goodwill / us-gaap_StatementOperatingActivitiesSegmentAxis = us-gaap_SegmentDiscontinuedOperationsMember
Rig Systems [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,279us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember	1,097us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember
Goodwill acquired during period		179us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember
Currency translation adjustments and other	(43)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember	3us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember
Goodwill, Ending Balance	1,236us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember	1,279us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigSystemsMember
Rig Aftermarket [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	906us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember	649us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember
Goodwill acquired during period		256us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember
Currency translation adjustments and other	(29)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember	1us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember
Goodwill, Ending Balance	877us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember	906us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_RigAfterMarketMember
Wellbore Technologies [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	4,425us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember	3,769us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember
Goodwill acquired during period	17us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember	665us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember
Currency translation adjustments and other	(85)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember	(9)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember
Goodwill, Ending Balance	4,357us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember	4,425us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_WellboreTechnologiesMember
Completion & Production Solutions [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	2,106us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember	1,314us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember
Goodwill acquired during period	150us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember	803us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember
Goodwill disposed of during the period	(71)us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwill1 / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember
Currency translation adjustments and other	(116)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember	(11)us-gaap_GoodwillTranslationAndPurchaseAccountingAdjustments / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember
Goodwill, Ending Balance	$ 2,069us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember	$ 2,106us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = nov_CompletionAndProductionSolutionsMember

X

- Definition

Amount classified as goodwill attributable to disposal group held for sale or disposed of.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1436-107760



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	instant

X

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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X

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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X

- Definition

Amount of increase (decrease) from foreign currency translation adjustments and purchase accounting adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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