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Subsequent Event (Details) (Ameron [Member], USD $) In Millions, except Per Share data	Sep. 30, 2011
Ameron [Member]
Subsequent Event (Textuals) [Abstract]
Cash on hand for acquisition of Ameron	$ 777
Earning per share	$ 85.00
Number of shares outstanding of company to be acquired	9.1

X

- Definition

Business Acquisition Cost Of Acquired Entity Cash Payable Per Share.

+ Details

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Namespace Prefix:	nov
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Number of shares outstanding of company to be acquired.

+ Details

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Namespace Prefix:	nov
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Subsequent event.

+ Details

Name:	nov_SubsequentEventTextualsAbstract
Namespace Prefix:	nov
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Balance Type:	debit
Period Type:	instant