Quarterly Financial Data - Summarized Quarterly Result (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,006us-gaap_Revenues	$ 1,070us-gaap_Revenues	$ 952us-gaap_Revenues	$ 1,077us-gaap_Revenues	$ 1,041us-gaap_Revenues	$ 1,113us-gaap_Revenues	$ 1,070us-gaap_Revenues	$ 1,072us-gaap_Revenues	$ 4,105us-gaap_Revenues	$ 4,296us-gaap_Revenues	$ 3,414us-gaap_Revenues
Operating expenses
Cost of products	801us-gaap_CostOfGoodsSold	857us-gaap_CostOfGoodsSold	759us-gaap_CostOfGoodsSold	869us-gaap_CostOfGoodsSold	844us-gaap_CostOfGoodsSold	907us-gaap_CostOfGoodsSold	874us-gaap_CostOfGoodsSold	874us-gaap_CostOfGoodsSold	3,286us-gaap_CostOfGoodsSold	3,499us-gaap_CostOfGoodsSold	2,803us-gaap_CostOfGoodsSold
Operating and warehousing costs	110dnow_WarehousingAndDistributionCosts	108dnow_WarehousingAndDistributionCosts	105dnow_WarehousingAndDistributionCosts	102dnow_WarehousingAndDistributionCosts	104dnow_WarehousingAndDistributionCosts	104dnow_WarehousingAndDistributionCosts	103dnow_WarehousingAndDistributionCosts	101dnow_WarehousingAndDistributionCosts	425dnow_WarehousingAndDistributionCosts	412dnow_WarehousingAndDistributionCosts	315dnow_WarehousingAndDistributionCosts
Selling, general and administrative	69	55	45	44	43	39	40	39	213	161	128
Operating profit	26us-gaap_OperatingIncomeLoss	50us-gaap_OperatingIncomeLoss	43us-gaap_OperatingIncomeLoss	62us-gaap_OperatingIncomeLoss	50us-gaap_OperatingIncomeLoss	63us-gaap_OperatingIncomeLoss	53us-gaap_OperatingIncomeLoss	58us-gaap_OperatingIncomeLoss	181us-gaap_OperatingIncomeLoss	224us-gaap_OperatingIncomeLoss	168us-gaap_OperatingIncomeLoss
Other income	(2)us-gaap_OtherOperatingIncomeExpenseNet	(1)us-gaap_OtherOperatingIncomeExpenseNet			(2)us-gaap_OtherOperatingIncomeExpenseNet	(4)us-gaap_OtherOperatingIncomeExpenseNet	2us-gaap_OtherOperatingIncomeExpenseNet	2us-gaap_OtherOperatingIncomeExpenseNet	(3)us-gaap_OtherOperatingIncomeExpenseNet	(2)us-gaap_OtherOperatingIncomeExpenseNet	(3)us-gaap_OtherOperatingIncomeExpenseNet
Income before income taxes	24	49	43	62	48	59	55	60	178	222	165
Provision for income taxes	8us-gaap_IncomeTaxExpenseBenefit	17us-gaap_IncomeTaxExpenseBenefit	16us-gaap_IncomeTaxExpenseBenefit	21us-gaap_IncomeTaxExpenseBenefit	14us-gaap_IncomeTaxExpenseBenefit	20us-gaap_IncomeTaxExpenseBenefit	22us-gaap_IncomeTaxExpenseBenefit	19us-gaap_IncomeTaxExpenseBenefit	62us-gaap_IncomeTaxExpenseBenefit	75us-gaap_IncomeTaxExpenseBenefit	57us-gaap_IncomeTaxExpenseBenefit
Net income	$ 16us-gaap_NetIncomeLoss	$ 32us-gaap_NetIncomeLoss	$ 27us-gaap_NetIncomeLoss	$ 41us-gaap_NetIncomeLoss	$ 34us-gaap_NetIncomeLoss	$ 39us-gaap_NetIncomeLoss	$ 33us-gaap_NetIncomeLoss	$ 41us-gaap_NetIncomeLoss	$ 116us-gaap_NetIncomeLoss	$ 147us-gaap_NetIncomeLoss	$ 108us-gaap_NetIncomeLoss
Earnings per share
Basic earnings per common share	$ 0.15us-gaap_EarningsPerShareBasic	$ 0.30us-gaap_EarningsPerShareBasic	$ 0.25us-gaap_EarningsPerShareBasic	$ 0.38us-gaap_EarningsPerShareBasic	$ 0.32us-gaap_EarningsPerShareBasic	$ 0.37us-gaap_EarningsPerShareBasic	$ 0.31us-gaap_EarningsPerShareBasic	$ 0.37us-gaap_EarningsPerShareBasic	$ 1.07us-gaap_EarningsPerShareBasic	$ 1.37us-gaap_EarningsPerShareBasic	$ 1.01us-gaap_EarningsPerShareBasic
Diluted earnings per common share	$ 0.14us-gaap_EarningsPerShareDiluted	$ 0.30us-gaap_EarningsPerShareDiluted	$ 0.25us-gaap_EarningsPerShareDiluted	$ 0.38us-gaap_EarningsPerShareDiluted	$ 0.32us-gaap_EarningsPerShareDiluted	$ 0.36us-gaap_EarningsPerShareDiluted	$ 0.31us-gaap_EarningsPerShareDiluted	$ 0.37us-gaap_EarningsPerShareDiluted	$ 1.06us-gaap_EarningsPerShareDiluted	$ 1.37us-gaap_EarningsPerShareDiluted	$ 1.00us-gaap_EarningsPerShareDiluted
Weighted-average common shares outstanding, basic	107,000,000	107,000,000	107,000,000	107,000,000	107,000,000	107,000,000	107,000,000	107,000,000	107,058,843	107,053,031	107,053,031
Weighted-average common shares outstanding, diluted	108,000,000	108,000,000	108,000,000	107,000,000	107,000,000	107,000,000	107,000,000	107,000,000	107,556,144	107,468,868	107,468,868

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Total costs related to goods produced and sold during the reporting period.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The net result for the period of deducting operating expenses from operating revenues.

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The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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