Segment Information (Financial information by segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information
Equipment rentals	$ 1,125	$ 1,005
Sales of rental equipment	116	110
Sales of new equipment	33	26
Contractor supplies sales	18uri_SalesRevenueGoodsNetSalesofSupplies	19uri_SalesRevenueGoodsNetSalesofSupplies
Service and other revenues	23us-gaap_MaintenanceRevenue	18us-gaap_MaintenanceRevenue
Total revenues	1,315us-gaap_SalesRevenueNet	1,178us-gaap_SalesRevenueNet
Gross profit	524us-gaap_GrossProfit	448us-gaap_GrossProfit
Assets	12,282us-gaap_Assets		12,467us-gaap_Assets
Operating Segments
Segment Reporting Information
Equipment rentals	1,125	1,005
Sales of rental equipment	116	110
Sales of new equipment	33	26
Contractor supplies sales	18	19
Service and other revenues	23	18
Total revenues	1,315	1,178
Depreciation and amortization expense	304	277
Capital expenditures	345	351
Assets	12,282		12,467
Operating Segments \| General rentals
Segment Reporting Information
Number of geographic regions entity operates in (locations)	12
Equipment rentals	976	924
Sales of rental equipment	108	106
Sales of new equipment	26	24
Contractor supplies sales	15	17
Service and other revenues	19	17
Total revenues	1,144	1,088
Depreciation and amortization expense	262	259
Capital expenditures	311	331
Assets	10,788		10,935
Operating Segments \| Trench, power and pump
Segment Reporting Information
Equipment rentals	149	81
Sales of rental equipment	8	4
Sales of new equipment	7	2
Contractor supplies sales	3	2
Service and other revenues	4	1
Total revenues	171	90
Depreciation and amortization expense	42	18
Capital expenditures	34	20
Assets	1,494		1,532
Equipment rentals
Segment Reporting Information
Gross profit	446	379
Equipment rentals \| Operating Segments
Segment Reporting Information
Gross profit	446	379
Equipment rentals \| Operating Segments \| General rentals
Segment Reporting Information
Gross profit	383	344
Equipment rentals \| Operating Segments \| Trench, power and pump
Segment Reporting Information
Gross profit	$ 63	$ 35

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Revenue derived from maintenance services provided under contracts or arrangements with clients. For example, it may include the maintenance of software, plant and equipment, and facilities.

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The total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue.

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The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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