Line of credit facility covenant terms minimum asset coverage ratio.

No definition available.

Name:	dnow_LineOfCreditFacilityCovenantTermsMinimumAssetCoverageRatio
Namespace Prefix:	dnow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility covenant trigger percentage.

+ References

No definition available.

+ Details

Name:	dnow_LineOfCreditFacilityCovenantTriggerPercentage
Namespace Prefix:	dnow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit amount unused expressed as a percentage.

+ References

No definition available.

+ Details

Name:	dnow_LineOfCreditUnusedCapacityPercentage
Namespace Prefix:	dnow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum debt to capitalization ratio allowable.

+ References

No definition available.

+ Details

Name:	dnow_MaximumDebtToCapitalizationRatioAllowable
Namespace Prefix:	dnow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage increase in commitment fee.

+ References

No definition available.

+ Details

Name:	dnow_PercentageIncreaseInCommitmentFee
Namespace Prefix:	dnow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of equity in customary security interest.

+ References

No definition available.

+ Details

Name:	dnow_PercentageOfEquityInCustomarySecurityInterest
Namespace Prefix:	dnow_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Senior secured revolving credit facility commitment.

+ References

No definition available.

+ Details

Name:	dnow_SeniorSecuredRevolvingCreditFacilityCommitment
Namespace Prefix:	dnow_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
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

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility first became available, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInitiationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=dnow_SwingLineLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=dnow_AccordionDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Additional Information (Detail) - USD ($)		6 Months Ended	12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Jan. 20, 2016	Jun. 30, 2017	Dec. 31, 2015
Debt Instrument [Line Items]
Agreement date		Apr. 18, 2014
Minimum asset coverage ratio	150.00%
Maximum capitalization ratio	45.00%		50.00%
Base rate	0.75%
Percentage increase in commitment fee	0.05%
Percentage of equity in customary security interest	65.00%
Senior secured revolving credit facility commitment		$ 750,000,000
Line of Credit Facility, Expiration Date		Apr. 18, 2019
Minimum [Member]
Debt Instrument [Line Items]
Line of credit covenant trigger percentage		25.00%
Standby Letters of Credit
Debt Instrument [Line Items]
Line of credit facility borrowings	$ 40,000,000
Swing Line Loan
Debt Instrument [Line Items]
Line of credit facility borrowings	$ 25,000,000
Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility borrowings		$ 128,000,000
Line of Credit Facility, Available Borrowing Capacity		$ 437,000,000
Line Of credit Unused Capacity Percentage		77.00%
Accordion Debt [member]
Debt Instrument [Line Items]
Senior secured revolving credit facility commitment		$ 250,000,000