Commitments and Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014 retirement_plan	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Number of defined contribution plans sponsored by company	2uri_NumberofDefinedContributionPlans
Defined contribution plan, contributions	$ 19	$ 17	$ 11

Defined Contribution Plan and Deferred Profit Sharing Plan, Employer Contribution Amount

No definition available.

Name:	uri_DefinedContributionPlanandDeferredProfitSharingPlanEmployerContributionAmount
Namespace Prefix:	uri_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration