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v3.20.2

Property, Plant and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Property Plant And Equipment [Line Items] |  |
Assets held-for-sale | $ 6 | $ 34
International [Member] |  |
Property Plant And Equipment [Line Items] |  |
Assets held-for-sale | $ 2 |

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- Definition Amount of assets held-for-sale that are not part of a disposal group. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 15 -Paragraph 4 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121558832&loc=d3e400-110220 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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- Details
Name: | srt_StatementGeographicalAxis=dnow_InternationalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |