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Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended			9 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2014	Feb. 20, 2013
Commitment And Contingencies [Line Items]
Rental expense related to operating leases	$ 390,000,000us-gaap_LeaseAndRentalExpense	$ 336,000,000us-gaap_LeaseAndRentalExpense	$ 281,000,000us-gaap_LeaseAndRentalExpense
Rig Technology [Member]
Commitment And Contingencies [Line Items]
Gain from legal settlement included in revenue				102,000,000us-gaap_ProceedsFromLegalSettlements / us-gaap_StatementBusinessSegmentsAxis = nov_RigTechnologyMember
Maximum [Member] | Robbins and Myers [Member]
Commitment And Contingencies [Line Items]
Alleged violations involved in goods 2005 and 2006						75,000nov_AllegedViolationsInvolvedInGoods / us-gaap_BusinessAcquisitionAxis = nov_RobbinsAndMyersMember / us-gaap_RangeAxis = us-gaap_MaximumMember
DOJ [Member] | Robbins and Myers [Member]
Commitment And Contingencies [Line Items]
Litigation settlement expense					1,033,000us-gaap_LitigationSettlementExpense / us-gaap_BusinessAcquisitionAxis = nov_RobbinsAndMyersMember / dei_LegalEntityAxis = nov_DepartmentOfJusticeMember
BIS [Member] | Robbins and Myers [Member]
Commitment And Contingencies [Line Items]
Litigation settlement expense					$ 600,000us-gaap_LitigationSettlementExpense / us-gaap_BusinessAcquisitionAxis = nov_RobbinsAndMyersMember / dei_LegalEntityAxis = nov_BureauOfIndustryAndSecurityMember

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Alleged violations involved in goods

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

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Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

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Cash received for the settlement of litigation during the current period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

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