Goodwill and Intangibles - Net Book Values of Identified Intangible Assets by Segment and Major Classification (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance	$ 68us-gaap_FiniteLivedIntangibleAssetsNet		$ 74us-gaap_FiniteLivedIntangibleAssetsNet
Additions	10
Gross	90	80	80
Accumulated Amortization	(5)	(6)	(6)
Finite lived intangible assets,Ending balance	73us-gaap_FiniteLivedIntangibleAssetsNet		74us-gaap_FiniteLivedIntangibleAssetsNet
Net Book Value	73us-gaap_FiniteLivedIntangibleAssetsNet		74us-gaap_FiniteLivedIntangibleAssetsNet
United States [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance	50		53
Additions	10
Accumulated Amortization	(3)	(3)
Finite lived intangible assets,Ending balance	57		53
Net Book Value	57		53
Canada (Member)
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance		2	3
Accumulated Amortization	(1)	(1)
Finite lived intangible assets,Ending balance	1	2	3
Net Book Value	1	2	3
International [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance		16	18
Accumulated Amortization	(1)	(2)
Finite lived intangible assets,Ending balance	15	16	18
Net Book Value	15	16	18
Tradenames, Trademarks and Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance		57	60
Gross	61	63	63
Accumulated Amortization	(9)	(6)	(3)
Finite lived intangible assets,Ending balance	52	57	60
Net Book Value	52	57	60
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance		10	11
Gross	24	13	13
Accumulated Amortization	(4)	(3)	(2)
Finite lived intangible assets,Ending balance	20	10	11
Net Book Value	20	10	11
Other (Covenant Not to Compete) [Member]
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets,Beginning balance		1	3
Gross	5	4	4
Accumulated Amortization	(4)	(3)	(1)
Finite lived intangible assets,Ending balance	1	1	3
Net Book Value	$ 1	$ 1	$ 3

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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

- Definition

Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, resulting from a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_FinitelivedIntangibleAssetsAcquired1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=dnow_TradenamesTrademarksAndPatentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_OtherIntangibleAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=dnow_InternationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: