Debt - Additional Information (Detail) - USD ($)	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Capitalization ratio, Maximum	60.00%
Capitalization ratio, Actual	24.60%
Outstanding letters of credit under various bilateral letter of credit facilities	$ 491,000,000
Unsecured Debt [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Instrument [Line Items]
Fair value of Unsecured Senior Notes	2,355,000,000	$ 2,211,000,000
Five Year Unsecured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, borrowing capacity	$ 3,000,000,000.0
Credit facility, Period	5 years
Credit facility, maturity date	Jun. 27, 2022
Credit facility, extendable borrowing capacity	$ 4,000,000,000.0
Variable rate basis	LIBOR, NIBOR or CDOR plus
Interest rate under multi currency facility	LIBOR, NIBOR or CDOR plus 1.125%
Borrowings under commercial paper	$ 0
Outstanding letters of credit issued	0
Funds available under revolving credit facility	$ 3,000,000,000.0
Five Year Unsecured Revolving Credit Facility [Member] \| Canadian Dollar Offered Rate (CDOR) [Member]
Debt Instrument [Line Items]
Variable rate	1.125%

Interest rate under multicurrency facility.

No definition available.

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- Definition

Line of credit facility covenant compliance debt to capitalization percentage.

+ References

No definition available.

+ Details

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- Definition

Line of credit facility covenant terms maximum debt to capitalization percentage.

+ References

No definition available.

+ Details

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Namespace Prefix:	nov_
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- Definition

Line of credit facility extended borrowing capacity.

+ References

No definition available.

+ Details

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Namespace Prefix:	nov_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Outstanding letters of credit under various bilateral committed letter of credit facilities.

+ References

No definition available.

+ Details

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Namespace Prefix:	nov_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(2))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a)(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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