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Income Taxes - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Effective tax rate	(5.50%)	0.60%

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- Definition

Effective tax rate continuing operations.

+ References

No definition available.

+ Details

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Namespace Prefix:	dnow_
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Balance Type:	na
Period Type:	duration

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- References

No definition available.

+ Details

Name:	us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration