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v3.21.1

Income Taxes - Additional Information (Detail) | 3 Months Ended
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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_
Data Type: | num:percentItemType
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